Exercise and weight loss Part 3: Fat

Fueled by fat:  Fat burning 101

There are many reasons to want to burn fat during exercise.  For obvious reasons, in the context of the series I'm currently doing, people want to burn fat during exercise to lose weight.  In that regard, one must emphasize that as much as we talk about weight loss, fat burning (or rather, a change in body composition) is the priority for most people who commit to exercise and diet to lose weight.

I must emphasize (and this is a late addition to the post) that the principles we've been speaking about in our previous three posts in this series do not suddenly cease to exist - in other words, the fundamental issue is still total calorie balance, not necessarily fat burned.  And so this post looks at fat use during exercise, but I don't want to overplay the concept that you can burn fat to accelerate fat loss.  In fact, in the long term, it's the creation of the calorie deficit that is needed, as we discussed in Part 2 A and B of this series.  If in doubt, read the whole series as one "book" and it should be clearer...

For those who are more interested in performance, fat burning is equally important. Ever since the 1970s, when the muscle biopsy technique first allowed scientists to "look inside" our muscles during exercise, we have understood that fatigue and performance are associated with a depletion in the body's glycogen stores.  Delaying this depletion of your body's carbohydrate stores is seen as an important adaptation to training, and we know that highly trained endurance athletes have a much greater capacity to use fat.  This is also the reason why science has looked at all kinds of strategies, like caffeine use, fat-loading, high fat diets and fat during exercise to try to delay carbohydrate depletion.

So, having made the case for fat burning, let's look at how it plays out.

A car with multiple fuel tanks:  Fat vs carbs

You'll know that our body is capable of using numerous sources of energy during exercise - think of your body as a car with multiple fuel tanks.  The first tank is glycogen, the storage form of carbs in the muscle and liver.  The second is fat (strictly speaking, it is free fatty acids), which is stored in the muscle and in adipose tissue as triglyceride.  This is summarized in the diagram below.

The problem we face is that our body's glycogen stores are finite - muscle and liver glycogen supply energy for exercise for about two hours (depending, of course, on the intensity, level of training and habitual diet, among other factors), and once they are depleted, hypoglycemia (from liver glycogen depletion) and fatigue are the result. 

On the other hand, much to most people's dismay, fat stores are not limited.   "Infinite" is not the correct word, because they're not, but in terms of physiology, you have more than enough fat to power exercise for much longer than you can ever exercise, even if you're an elite athlete.  Most of us are not, and so our objective is to cut down these already abundant fat stores into something a little more "acceptable"!

For now, I won't go into the concept of "preferred fuels" and how the heart can use lactate, while the brain is able to use ketone bodies.  I've also oversimplified by leaving protein out, but that's because I want to focus on fat vs carbs today.



Burning fat - how fast, how long?


Perhaps the best approach to this topic is to ask when each of the fuel stores is used?  In otherwords, how does your body decide when to use fats versus carbs as a source of fuel, and to 'fuel' the discussion by starting with some of the theories around fat burning.

The first theory is that you burn more fat when you exercise at a low intensity.  That is, walking is better than running, and cycling slowly is better than cycling fast, and so on.  The idea is that your body uses carbs more and more as exercise intensity rises - this is the basis for target heart zones and the fat burning zone you see in books and on gym equipment.

Let's look at that in more detail.  Below is a diagram that shows an example of how the use of fat and carbs are related as exercise intensity rises. 

So, on the left, in the pink shaded box, you can see that at low intensities (walking, slow cycling), about 80% of your energy comes from fat, while only 20% comes from that carbohydrate (CHO) "tank".  As the exercise intensity rises, the relative contribution of fat falls while CHO rises.  The result is that at about 60%, shown by the green zone, the contribution is equal - 50% from fat, 50% from CHO.  This point, at which the contribution from CHO becomes greater than that from fat, was called the Cross-over point by George Brooks, a very famous exercise physiologist, who wrote a great textbook on the field (the book that was prescribed to us in my studies, in fact).

Then, as exercise intensity rises even more, the contribution from fat declines, so that by the time you're exercising vigorously, between 80 and 90% of the energy comes from CHO, and only about 15% from fat.

Just to comment on how you can measure intensity, my value is calculated as a percentage of VO2max, which is not accessible to many people.  It's impossible to say exactly what heart rate that corresponds to, because it is very much dependent on the person and the context of exercise.  For some, it's a one-to-one relationship, so that 50% VO2max is 50% HRmax, whereas for others, heart rate will be higher than VO2max - 50% of VO2max would correspond to say 60% of heart rate max.  I wouldn't get too hung up about this, for reasons explained below.  I know it sounds simple, but if you're wondering what 60% corresponds to, it's 6 out of 10 on a scale of exertion, where 10 is maximum effort.

Note also that the cross-over point, and in fact the whole pattern of the two lines is quite 'malleable' in that training, diet and genetic differences affect the relative percentage.  For example, a highly trained athlete burns fat more efficiently than an untrained person, and so they tend to use more fat at a given intensity.  People who habitually eat high fat diets are also shifted to the right, meaning that they burn more fat at a given intensity.  Sympathetic nervous system activity does the reverse, shifting the lines to the left, so that you burn more CHO and less fat at any intensity.  So the point is, the above graph is an example, not an absolute guide.

Low intensity is better, right?

So, what you're probably thinking is that theory that low intensity exercise is better if you want to burn fat is correct.  Well, think again.  It is true that at low intensity, when you walk, most of your energy comes from fat, and that as you increase the intensity, less and less comes from fat.

But what is missing in this picture is the TOTAL amount of energy.  Let me phrase it this way:  Would you rather have 20% of the money in Jonathan's bank account, or 80% of the money in my bank account?

Your answer of course, should be that you don't know.  And what you should be asking is "How much money is in your bank accounts?".  The reason is, you'd be pretty annoyed if you took 80% of my money, because my bank account might be empty.  Jonathan, on the other hand, might be loaded, and 20% of his money sees you retiring at 40! (Truth is, neither of us retiring early, which is why your donations are welcome! Kidding...)

So, look at the graph again.  You should not be too pre-occupied with the percentage, but rather the total amount of fat that you are burning, because that 50% that comes from fat in the green zone might be more than the 20% that comes from fat in the pink zone.  For answer to that, we look at a study done many years ago by Romijn.

Below is a graph that I've redrawn with some calculated figures, based on Romijn's study.

So, you're looking at the same kind of graph as before, showing how much of your energy comes from fat and CHO at different intensities (I've further divided it into muscle, liver and adipose sources, but that detail is not vital right now.  Note, however that "Plasma FFA" refers to the fatty acids that originate from the adipose tissue - the triglyceride is broken down into free fatty acids which are used).   This time though, there is also a measure of HOW MUCH total energy is being used, shown by the y-axis (in kCal/hour, for an 80kg man in this case)

So again, at low intensities (25% VO2max), you'll see again that most of the energy comes from fat (75% in this case), with only 25% from CHO.  Jump to 60% and the fat contribution falls to 48% and then at 85%, fat provides only 20% of the total energy.  This confirms what we saw in the first graph.

But, the key is that the TOTAL energy, shown here on the y-axis, rises as well, and so the 48% of energy from fat that you get at moderate intensity actually adds up to more TOTAL fat use than the 25% did at low intensity.  Think of the y-axis (total energy) as the size of the bank account, if you will.  The green boxes above each bar show the total amount of fat burned in an hour - 24g, 37g and 23g per hour at the three intensities.

The moral of the story, which is shown further in the graph below, is that if your objective is to maximize fat burning, low intensity is not necessarily the best option.  Rather, moderate intensity burns more fat per hour, before a decline in fat use as the intensity rises beyond about 60%. The reasons for these shifts, incidentally, include increased sympathetic response to exercise, activation of different muscles as intensity increases, local regulation of metabolism in the muscle, and also the exponential nature of physiological responses to an increase in intensity.  That's a post of its own!

Remember also that these are graphs based on calculations and measurements for a typical person - the actual values may vary for different people depending on training, diet and sympathetic activity, as mentioned.  One also has to make some assumptions, such as VO2max values, the RER during exercise and how it changes with intensity.  But I want to highlight the principle, not the values, so bear with those assumptions.

What does this all mean?  The role of time and putting it into perspective with diet

So, what this means is that if your goal is maximum fat use, then lower intensities may mean a greater relative contribution, but it is moderate intensity that gives you greater fat use per unit time.

Time is key though, as many of you are no doubt thinking.  If you do a low intensity session, walking (25% VO2max in the above graphs), then while your total fat use per hour is not as high as at say 60%, you might be able to do this exercise for three hours, compared to only one hour at a moderate intensity.  Three hours with 24 g per hour (see figure) beats one hour with 37g.  So duration plays an equally important role.  What I am emphasizing is that for a given time, you will be better off at a moderate intensity somewhere between 50% and 65%.

The next point, before we get too carried away, is that the actual differences are pretty small.  Not to discourage you too much, because exercise is vital for weight management and health, but one rule of thumb is that you can estimate total energy use during running by saying that you burn 1 kcal per kilometer per kilogram.

So, taking our 80kg man, who runs 8km (5 miles), he'll burn about 640 kcal.  It doesn't matter how fast he runs, thid amount is the same (the difference, of course, will be how much time he spends burning it).  Now, assume that half his energy comes from fat and half from carbohydrates.  That means 320 kCal from fat, corresponding to 35 g (this is about the same as in the graph, since I based that graph on this kind of calculation).

So, 35 g of fat in 8 km or 5 miles.  To burn 1 kg of fat, he therefore has to run 230 km (142 miles).  Not very encouraging.  There is an additional 'after exercise' effect, which one can't ignore, but I want to make the point that actually burning fat is not as simple as we often assume.  In the words of Bengt Kayser, who pointed out this principle, it puts into perspective the resolution that says "I want to burn off 10kg of fat by running".

You can work out a similar thing for cycling.  If you ride for an hour at 200W, your energy use is probably going to be about 800 kcal.  If 50% of this comes from fat, then you've got 400kCal, or about 44g of fat.  That is about the same rate of fat use as your 8km run gives you, and a lot of cycling to burn those 10kg of fat.

The value is in energy, not necessarily one fuel

And then perhaps most significantly, the key is still to create a calorie deficit, which means that you need not worry too much about whether your energy use is coming from fat or carbs - the key is to create that deficit, because in the long run, the energy will have to be provided and you will achieve similar results regardless.  Again, I'm oversimplifying a little, because we have discussed how efficiency changes, and there are some issues as to how the nutrients are oxidized as they are ingested, but the principle is not necessarily to burn the most fat, but to create an energy deficit.

And this is where diet comes into the picture.  If you want to create the energy deficit in order to lose weight, and notwithstanding that this is an oversimplification as we described in Part 2B of this series, then the combination of diet and exercise the way to do it, because to actually burn energy directly is a lot more difficult than people think.  This is why the combination, and the long-term approach is so important.  Things do not happen overnight in physiology, particularly when it comes to weight loss.

The progress can be slow, and invariably, when it is not, it's not sustainable.  Crash dieting, starvation might lead to rapid results, but they also lead to subsequent rebounds, and health problems that we won't go into now.

But for the purposes of this post, which I'll wrap up because it's been rather heavy on numbers, the key point is that burning fat during exercise happens right across the range, and the ideal intensity, if you are looking to make the most of your time, is a moderate intensity, and not the low intensities that you'll often hear recommended.

Next time, we'll look a little more at energy use during exercise and the role of diet.

Ross

Exercise and weight loss, Part 2B

Calorie complexities

No, not part 3 of the weight loss series, don't worry.  Rather, it's a response to your many emails and comments to Part 2 of the series that looked at calories in, calories out, and the principle of weight loss.  As usual, there are too many good comments to do justice to with an answer, so I'll thank you once again and move ahead to a general response.  Also, I wanted to write briefly on what is still coming, because there are some things I want to cover in future posts which come up over and over in the early posts as well. 

One common theme in your responses has been 'complexity', and this is something that has weighed (pardon the pun!) on me as I've written these last two posts.  As I stressed yesterday, weight loss is not simple (obesity wouldn't be the fastest growing cause of death if it were), but at the same time, it must be simplified, because so many layers of misinformation have been added over the years (and the 87,000 books) that many have become entrenched as 'best practice' that it actually serves to go back before going forward!

The simplicity is the calories argument, the principle that energy out must exceed energy in for weight loss to occur.  However, I wouldn't recommend taking the approach of counting calories to try to balance the equation, because of inaccuracy and unknowns on both sides of the 'scale'.  I explained this a little yesterday, but there were two points that I didn't stress enough, and I have some of you to thank for raising them.

Energy sources

First, let's look hypothetically at someone whose energy intake is 3000 kCal per day, and who exercises regularly and is in weight balance.  This person could, in theory, get that energy from 333 grams of fat.  They could also get it from 750 g of starches.  Neither is desirable, for both the obvious reason that a diet consiting entirely of only one food group would be sorely lacking in important nutrients and you'd end up less healthy than Morgan Spurlock (the guy from Supersize Me).

However, what is more vital is to recognize that you don't simply add up the numbers, because the macronutrients (carbs, fats and proteins) have a more complex role than simply adding calories to the body.  Carbohydrates are the primary source of energy during exercise, and for the brain pretty much all the time.  Fats play a role in cell function, and proteins are crucial for cell repair and for muscle recovery after exercise.  You can have too little of each, particularly carbohydrates.  Perhaps the biggest trend in fad diets in recent years is the shift away from carbohydrates, with the principle that fat can provide energy.  That's true, but only up to a point, and an athlete without carbohydrates is a dangerous proposition - impaired performance and immune function are two of the consequences.

The point is that your objective with diet is not to simply tally up the calories, you also have to manage the diet for health reasons.  There are many theories on how to achieve this - there's a 40-30-30 principle, which says that 40% of your energy should come from carbs, and 30% each from fats and proteins.  Then there's the theory that those doing more exercise should aim for 60-30-10, then there are the "anti-carb" diets where only 10% of the energy comes from carbohydrates, with most from proteins.  There is a great deal of debate around these diets, which balance is optimal.  I'll try to get to that later in the series, or in a separate post in collaboration with a dietician (because if you want to offend people, tell them their diet is not optimal).  I firmly believe, however, that anyone who is basing their weight loss on exercise, or who is training for performance, must ensure that their carbohydrate intake is sufficient, or they will be compromised.

Now, before this becomes a post of its own, let me address the second point.

Complexity in calories

Take the case of a person who has recently come down from 250 to 230 lbs, and is attempting to lose a further 20 lbs (± 10 kg), through the use of diet and exercise.  But, much to their dismay, they lose nothing.  Some will say that this person has matched their calories in and calories out but not lost weight, thus discrediting the principle.

The problem is, you can never know with certainty what has happened to energy output.  Until you measure it exactly (which requires complex equipment and is highly impractical), you assume that calories out is accurate.  It may not be - there is a lot of evidence that muscle becomes more efficient when weight is lost, which would impact on how the estimation for energy expenditure is made.  Suddenly the energy intake is again greater than it should be.

Similarly, metabolic adaptations to conserve energy have been identified.  For example, a reduction in body weight (specifically, fat) causes a fall in the levels of two hormones, leptin and thyroid hormone.  Problem is, when these hormone levels fall, appetite rises and metabolic rate actually goes down.  If you inject leptin, incidentally, you can prevent this drop in metabolic rate (Rosenbaum, 2002 & Rosenbaum, 2005).  So, referring again to the figure from yesterday (shown again below, but with the modification after metabolic adjustments), your body actually reduces the resting energy expenditure in response to weight loss, which may create an energy surplus.

This is yet another reason why I don't advise the approach of counting calories to try to match the two sides - your body is too smart, and too complex for that in the longer term!  Trying to pre-emptively calculate the body's response is fraught with error, because of inaccuracy of measurement, and complexity of physiology.  Yesterday, I mentioned the example of an individual who remains weight stable over a 10 year period.  What I was getting at, but didn't put across correctly, is that weight balance is incredibly complex - over 9 million calories balanced in a ten-year period.  That doesn't happen by accident, and it doesn't happen by preemptive design.  It happens by physiology!  And so losing weight requires the same principle - don't micro-manage the scale, rather be sensible and allow the theory to work for you, not to work the theory!

Final word on appetite

Then finally, something I absolutely must cover (and hope to) is the "listen to your appetite" theory.  Your body is remarkable and it does signal to us when we need to rest, to eat, to drink, and even what (a salt craving for example, is part of the exquisitely regulated osmolality homeostat that sports drink companies don't want to recognize!).

However, in the case of diet, we're subjected to too many external influences that affect appetite that many people cannot rely solely on how they feel in order to eat correctly. There's some great research on this - Brian Wansink has done some studies with interesting titles like "Is this a meal or snack? Situational cues that drive perceptions.", and "How visibility and convenience influence candy consumption."  He has also written a book called Mindless Eating: Why We Eat More Than We Think, detailing this fascinating phenomenon.   (just a note - at the end of the series, I'll do a book list with some recommended reading on weight loss, looking at both exercise and diet)

Then there is the psychological component of food, which cannot be ignored, because our desire to eat is not simply 'physiological' in that stress and emotional cues trigger eating (we all know this as "comfort food", among other things).  I would argue that these are still physiological, mediated by neurotransmitters in the brain, but this is semantics.  Point is, we may not be able to trust that our body signals when to stop or to cut back.  And then finally, I've already mentioned that with reduced weight (and fat mass) comes a fall in leptin, which then increases our appetites, playing havoc with the theory as our weight changes.

All in all, a complex issue, and another one to tackle in detail later (if not in this series, then in another).

Looking ahead

So that's it for my "short" reply to your posts.  I just wanted to consolidate yesterday's posts, but I guess there were a couple of key points to make.  The principle of increasing energy expenditure and cutting down energy intake is without doubt the simple solution.  Achieving this is difficult (but this does not make the principle wrong, take note), and there is a physiological layer of complexity that makes it impossible to preemptively manage energy in and energy out.  What it boils down to is systematic sensible choice, with expert support to get the principles correct.

Part 3 on fat is on the way - probably later in the week, I have a presentation to work on first, so forgive the sudden "loss in momentum" of the series.  

Ross

Exercise and weight loss part 2

The calorie conundrum:  In vs Out

Thanks to everyone for your comments and emails in response to part 1 of our series on Weight loss and exercise.  It's always great to debate the issues, and in this particular case, I value your thoughts even more because it will help steer the remainder of this series in a direction that I hope meets most expectations.

I realized overnight what an enormous challenge this topic presents - there is simply too much content and too many angles to cover, and so I have no doubt that I will fail to do justice to some of the sub-plots in this fascinating area.  However, as I stressed yesterday, my approach here is to look at weight loss from a general point of view, not an elite one, because weight loss transcends performance boundaries.  Of course, it will feature, and I know many of you work in that performance realm - we're all about high performance here, so it will come up, but I hope to tap into a different area of exercise physiology in this series.

Perhaps one day, I can team up with a dietician and some researchers in this field and produce the book that covers ALL the angles!  Thinking back to yesterday's post, where I mentioned that there are already 84,000 books on weight loss, I think a good title for a book would be "The devolution of weight loss.  Back to basics", because it occurred to me that the evolution of the obesity pandemic has co-incided with the explosion in "knowledge", when all along, the answers are pretty basic.  Tough to implement, make no mistake, but basic in theory.

And that, the basic approach, is what I will try to unpack in this series, starting today with the basics of energy balance.

Calories in vs calories out:  Simple principle, with complex implications

I have no doubt that all of you know the basic premise behind the "scale" of weight loss, which says that your body mass is a function of the balance between the energy intake and the energy output on a daily, weekly, monthly or yearly basis.

On the left hand side of the scale, you have energy intake, in the form of food.  Each has a caloric 'implication' - 1 g of carbohydrate and protein adds 4 kCal, whereas 1 gram of fat contains 9 kCal (alcohol, incidentally, is 7 kCal/g).

On the right is energy output, and that is made up of resting energy expenditure (a combination of sleeping and awake), the thermic effect of food, because when we eat we actually increase energy use for a short period and different foods produce a different response.  And then finally, there is the energy expenditure from activity, which is where exercise fits in, and which is the most "malleable" of the different components - it can be zero, or it can be enormous, if you exercise like a Tour de France cyclist and burn 5000 kCal per day in training or racing!  This is shown in the diagram below.

The basic premise of weight loss is this:  weight loss requires that your energy output exceed your energy intake for a prolonged period.  Much like financial management, weight management is simply a balance between spending and saving - if you wish to save money, spend less than you earn.  If you want to lose weight, eat less than you burn (eat your heart out, Shakespeare.  Thanks Bruce!)

In any event, this principle is behind pretty much every strategy ever devised to lose weight.  Hours of exercise to add to the right hand side of the scale, or starvation diets or any one of the millions of other diets to reduce the left.  Or weight training to try to increase resting metabolic rate, and even eating specific foods like chillies to try to increase the thermic effect of food.  Some of these are more effective than others, as you can imagine, and it's the intelligent reduction in energy intake combined with the increase in energy expenditure that will ultimately lead to weight loss (and note that the operative word is "intelligent").

So, in Time magazine's controversial article, exercise took a knock because of what was called the compensation effect.  An hour of exercise could burn anything between 300 and 1500 kCal, depending what you do - run like a Kenyan and you'll be up at 1500 kCal, walk slowly and you're at the bottom end (this huge range illustrates one of the biggest problems with this calorie "counting" approach, as we'll see shortly).  The problem is that if you do this time, but don't also manage your diet, then it's possible to replace all that energy, and then some, with just one meal or snack.  The end result is that the scale tilts in the WRONG direction and you gain weight, not because of exercise, but because of the dietary choices you make in association with exercise!

For example, compare the following two ways to spend a Sunday afternoon:

So, on the left, the exercise option can be all but canceled out by diet, in this case a can of Coke.  In that regard, you'd be better off watching television for 30 minutes and eating nothing.  This was basically the take home message in Time's article, which clearly misses a big part of the picture.  If you make the same dietary choices by drinking a Coke in Option B where you remain inactive, then you shift in the other direction, and may gain weight.  All things being equal with regards to diet, exercise is valuable - how many people exercise as a reason to indulge in foods that they otherwise would not be able to?

Let me emphasize, however, that there are many other reasons why Option A is the better one - for one, you can't simply not eat in order to lose weight, and so Option B is not really feasible in the long term.  Second, life is not a game to see if you can balance your calories - there's more to it than that!  Third, the health benefits from exercise are not captured in a single number of calories out minus calories in.  These are all crucial aspects and I want to stress that one should not get too hung up on the minutiae, but rather understand the principle.

When details matter

All of this is obvious, and forgive me for oversimplifying the situation, but you'd be surprised at how easy it is to be tripped up by this simple principle.  If you are embarking on a weight loss plan, and have yet to see significant results despite diligently exercising for 45 minutes a day, then the answer is likely that you still haven't addressed the other side of the scale adequately.  If you have reached a plateau in weight loss, then the same may be true - it's time to consider how much you eat, when you eat it, and what you are eating, because you may unwittingly be negating your exercise with simple dietary practices.  And I must stress this - what you read in books and see on TV is generic advice - it can only take you so far.  There will come a point where you need specific advice and that is where consulting a dietician becomes vital, especially for the more complex situations.

Take for example a more serious athlete, who is looking to lose the final 2 or 3 kg to get down to racing shape.  They may train for 2 hours a day, and burn in excess of 2000 kCal during those two hours.  However, even a "healthy meal option" can put that back in one sitting.  Here in SA, we have a chain of health shops called Kauai, and most serious athletes would not think twice about eating there (think organic food, smoothies, rye breads and everything you read is healthy - I'm sure you have these stores in your country).

Problem is, a typical meal at one of these stores, consisting of a breakfast wrap and a low fat protein smoothie, adds back 1600 kCal.  The end result is that 2 hours of exercise goes nowhere, and our cyclist, despite training as hard as his body can tolerate, does not lose that weight.  The only solution here is to manage the details - portion sizes, content and even the timing of the meal.

For example, there is evidence that if you delay eating after exercise for about an hour, you burn more fat than if you eat right away.  This has to do with keeping insulin levels down, and insulin is a hormone that drives carbohydrate use, while "tuning down" fat use.  The problem is, if you delay eating, you may compromise your recovery, which means you can't sustain high quality training day after day.  You also can't cut carbohydrates out, and you certainly can't under eat - there is compelling evidence that the biggest risk factor for becoming sick during intensive training is an energy deficit.  

You may also have read that if you train before eating, you rely more on fat and this would lead to greater weight loss.  In theory, yes (it has to do with availability and insulin again), but practically, you might battle, because the risk of hypoglycemia is higher, you may not recover well from the metabolic stress, and because the body is often too smart to be tricked in the long term.  You therefore have a dilemma if you are trying to train hard and struggling with stubborn weight.  Each case would have to be managed on a case by case basis, and I can't stress enough that seeking out expertise to discuss these details is essential - generic advice only takes one so far, after which time books, websites and magazines can't help any longer.  Dieticians fulfill this role, although I will touch briefly on these issues in future posts, so don't worry, I'm not leaving you hanging completely!

Calorie counting - guaranteed weight loss or futile exercise?

Returning to the energy balance scale, everything I have written so far is probably steering you into thinking that if you simply measure what you eat, and measure how much you exercise, you can balance your own scale and lose weight.

And you'd be swimming into dangerous waters by doing this.  Let's look again at the scale - there are two sides that you would have to manage, Energy Intake and Energy Output.

On the Energy Intake side, you have the following problems:

1. You would have to cook all your own food and measure everything that goes into it, which means you can't eat out and you limit your options to only what you can measure
2. Not all foods have clear labels, so you would invariably miss certain measurements
   

On the energy output, the problems are even more numerous:

1. You can't know with certainty how much energy you have burned during exercise - there are reasonably accurate estimations, based on heart rate and many studies, but precision is beyond us
2. You cannot quantify the other aspects of this side of the scale (see the diagram above), particularly the resting energy expenditure and the thermic effect of feeding, which make up an enormous part of the total.  Get this wrong by even 5% and you're looking at a big error in your calculation.
   
3. There is a substantial increase in energy use AFTER exercise - this post-exercise elevation in metabolic rate is not accounted for by tables.  So you might run for 60 minutes and burn 800 kCal, but the actual total thanks to exercise is higher.  Quantifying this is a problem.

Now, the point is that you cannot measure these things accurately, and therefore you cannot micro-manage this.  Here's an illustration of the complexity:  An 80kg man who remains at the same weight for 10 years has, over this period, managed to balance a grand total of about 9.1 million kCal.  In contrast, if he gains 10 kg over this period, it's because of a mismatch of about 70,000 kCal.  In ten years, that works out at 19 kCal per day.

In other words, you can try to measure your calories in and calories out, but if you're systematically inaccurate by 20 kCal per day (the equivalent of a sip of Coke), you gain 10kg.  My point here is that counting calories, unless it's done with absolute precision, is not a good method to manage your weight.

Where calorie counting is helpful is in creating awareness about diet, and if there's one thing you remember from this series, it is that awareness is perhaps the most powerful ally you have in trying to lose weight.  There are studies, for example, that have found that having people write down what they eat every day (volumes, sizes and content) leads to significant weight loss, even though they are not told to do anything else differently.  Similarly, if you are on an exercise programme, and you write down what you do and what you eat, you lose more weight than if you exercise 'blindly'.  In both instances, it is awareness that helps, because it guides sensible food choices, smart exercise and it is this combination that helps to produce sustainable weight loss.

So knowing what you put into your body, and knowing how much you burn, can help guide you.  It may be the catalyst behind making sensible choices to reduce portion sizes, or change the content of your meals slightly, or maybe increasing the time you spend exercising.  If you have an idea that your daily energy intake is 2500 kCal (give or take, because as I've said, absolute precision is out of reach), and you're exercising for 30 minutes at a moderate intensity (± 400 kCal, added to a typical day of about 2000 kCal), then you can correctly deduce that you need to change something - either train for 40 minutes, or train slightly harder, or cut down on portion sizes, and you'll start to see results.

Next up - fat burning 101

Forgive me for what may seem a very basic approach - I did say that a book on this topic should be called "Back to basics", because so much complexity has been added to this by all kinds of gimmicks and 'revolutionary' ideas that hopefully it's a refreshing reminder that the actual principle behind weight loss (and the reason we often fail) is pretty straightforward.

I don't mean to trivialize the problem, though.  If it were simple, fewer people would struggle.  But the principle is straight-forward - implementing it, sticking with it, not quite as easy!

What we need to do next is discuss exercise and energy use, particularly around fat burning.  What intensity?  How long?  Do you only start burning fat after an hour?  How do you manipulate it?

That's coming up in Part 3.  Sorry for the long post - I wanted to split it into two, but it wouldn't have made sense.  And just so you know, you've probably burned 20 kCal while reading this!  But don't worry about the number!

Ross

Exercise and weight loss

Exercise, weight loss and common sense sensationalism

I've long felt that one of the biggest privileges of being in the field of exercise science is that what we (sports scientists, that is) study is relevant to just about everyone.  If botanists have flowers and gardens, if astronomers have planets and stars, then sports scientists have...performance, and weight loss.

For almost three years on this site, we've focused almost exclusively on performance aspects - elite athletes, pacing, doping, world records, technology, and have had little emphasis on weight loss.  But the reality is that if ever there was an area of exercise science that was relevant to everyone, it is weight loss.  Whether you are into optimal performance, where carrying 1kg of excess weight is the difference between winning and losing, or whether you are an individual who is told to lose 50 kg (110 lbs) to stay alive, weight loss features on everybody's horizon.

And so we turn our attention to the issue of weight loss and exercise, with our new series, which we hope provides food for thought, and maybe inspiration, regardless of which category you fall into!

The global pandemic and meeting the needs of the market

You've all heard the statistics, I am sure - that obesity is the fastest growing cause of death in America.  That two out of every three people in the USA is overweight or obese, and that this figure is rising, both in the US and the rest of the world.  However, statistics like these are often far removed from what would drive you to take up the weight loss challenge for yourself.  It's all good and well knowing that two in three colleagues may die from a preventable disease caused by obesity (and that you may be one of them), but the real driver for most people to lose weight is closer to home.  So as you read this, your primary concern may be the 5, 10, or 50 lbs that you are looking to lose.  And it's that angle that I wish to take in this series, without dismissing that there is a global problem that needs to be addressed.

Now, when it comes to weight loss, there is no lack of a demand - it is created by your desire to perform, to look better or to be healthier.  This market is enormous, a multi-billion dollar industry, and it borrows from science to pitch a dizzying array of exercise machines, programmes and diet plans at consumers, who, desperate for an answer (in a short space of time) will jump at anything that promises to meet their need.  For example, if you do a search on Amazon.com for "weight loss" and you will discover 83,798 books, which is up from 67,000 books back in May last year.  That means that 17,000 books have been added in under a year.  You will also find two TV games, 7 shoes, 6 items of jewellry and 180 music items which have some association with weight loss. 

One of these books is "The Cardio Free Diet", written by a Chicago-based personal trainer, named Jim Karas.  The book cover promises results in only 2 weeks (this is a classic tactic to hook consumers with), and it proclaims "real results in only 60 minutes a week", "lose the cardio, lose the weight", and "Kiss the treadmill goodbye".  The first line of the book, incidentally, is "Cardio kills.  Your joints, your time, your motivation, and your weight loss goals".

We may get into the details later in the series, but for now, suffice it to say that none of this is true.  Where a tiny element of truth exists, it has been twisted beyond all recognition, or buried beneath sensational advice in the interest of the angle.  This book was a bestseller.  Why?  Because it recognized the need, and then it pitched to consumer an idea that was almost irresistible - that they could lose weight in next to no time, with no cardio at all.  Consumers buy this book because they desperately want it to be true, and are willing to try anything to lose the weight they believe they must.

Unfortunately, this book, and many like it, covering topics like diet, exercise, equipment and medicine, represent "cutting edge knowledge" that has witnessed the greatest explosion in obesity we have ever seen.  Something is wrong with this picture...

Enter Time magazine and the "myth about exercise"

Into this environment, you introduce Time magazine in August, 2009.  A cover story, shown left, promised to reveal the "Myth about exercise", saying that it won't make you lose weight.  Inside, the article produced quotes from professors who said that "In general, for weight loss, exercise is pretty useless".  It told us that vigorous exercise would lead to weight gain, and it explained how years of advice to exercise to help with weight loss was only making us fatter.

It was, not surprisingly, met with a fair degree of condemnation within the exercise community.  I have no doubt, however, that it also attracted a fair amount of attention, and maybe led to the sale of a few Time Magazines that may otherwise not have been sold - remember, the market is saturated with advice and information on a very topical issue like weight loss.  Standing out in the crowd requires a hook, and telling thousands of people who have exercised for years that they are wasting their time is a pretty strong hook.

I bring this up only to make the point that the content of the article, and the angle which is uses to approach the subject must be understood in order to interpret what it said.

The compensation effect - a valuable insight on weight loss and exercise

The truth of the matter is that the article raised some very interesting points.  The central theme is what was called "the compensation effect", the phenomenon where people who exercise without concern for how they manage their diet MAY (not WILL, as the article suggests) actually overshoot their requirement and begin to overeat.  The result may be weight gain, or failure to lose weight.

The article cites one or two studies, in adults and in children, where this has happened - exercise fails to induce weight loss, and one theory is that our subconscious energy intakes simply rise to match expenditure.  The article also includes a few quotes from highly respected scientists.  Take for example the following quote from Prof Timoth Church of the Pennington Biomedical Research Center, who is the author of one of the quoted studies:

"I see this anecdotally amongst, like, my wife's friends," he says. "They're like, 'Ah, I'm running an hour a day, and I'm not losing any weight.'" He asks them, "What are you doing after you run?" It turns out one group of friends was stopping at Starbucks for muffins afterward. Says Church: "I don't think most people would appreciate that, wow, you only burned 200 or 300 calories, which you're going to neutralize with just half that muffin."

There is nothing incorrect with this at all - it's true.  It's common sense.  But common sense doesn't sell very well, and it certainly doesn't stimulate huge debate, which is why the context of these quotes was changed in the article.

But the point I am making is that the article is not nonsensical and completely false.  It actually contains some vital information, which may have been overlooked in the heat of the debate.  The bias of the article is shown in the fact that the author, on numerous occasions, writes that "exercise won't make you thin".  One word would have changed everything, because had he written "exercise might not make you thin", the statement would have been accurate!

Weight maintenance and health - what was left out

The other major criticism of the article is what it left out, rather than what it included.  This is often the case of course - it's what you DON'T say that causes the problems!  And in this particular article, there was no mention at all of numerous studies that have found that exercise is beneficial for weight loss, and crucially, weight maintenance, as well as health of physically active people.  A vast body of research exists to show how exercise improves weight maintenance, working hand in hand with diet and other lifestyle choices to help people get to, and then stay at, an optimal body weight.

Then there is plenty of evidence that shows how physical activity improves health - blood pressure, lung and heart function, cholesterol (lipid) profiles, insulin sensitivity, muscle and bone strength, and so forth.  These studies even challenge the notion that weight loss should be a focal point for people who are exercising.  They suggest that it is better to be fit, even if you are overweight, than it is to be within normal weight and unfit or inactive.  However, this did not feature at all in the article.

Where to next?  Unpacking the theory

So, having pointed out what was missing in the article, and how facts may have been embellished for the sake of sensation, we need to actually unpack the compensation effect.

So that will be the next part of the series - the theory of weight loss.  This includes the infamous "calories in vs calories out" equation, the so-called energy balance, and the source of so much frustration and over-analysis.  But the principle is vital, and that's something to look at, especially to consider how exercise and diet interact to change this energy balance.

Then, we'll look also at the benefits of exercise - the health impact of regular physical activity, which was so completely overlooked by the Time magazine article.   For now, this was an introduction, a quick glance back at the Time piece, which sets the scene for the series to come.

Ross

Science of Sport humour

Innovation and truth in physiology: (and a humorous, great tip for fat loss, straight out of the 1930's)

Since it's a Friday afternoon, and few people are focused on anything serious, I thought I'd do something of a humorous post today, linked to what people have been writing in recently about "fact vs fiction" when it comes to human physiology (which is our staple diet, after all).

We have a big week ahead of us, and so we're saving some of the more in-depth analysis for next week, when you can look forward to:

• A discussion of the Kenyan "failures" on the track in Olympic and World Champions in the last 15 years. Why has Kenya won only ONE out of the last ELEVEN major titles at 10,000m, for example?
  
• More analysis on Oscar Pistorius, who runs tonight in Rome. The picture is slowly emerging on the "science" he produced to legally clear his way at the CAS. Next week, we'll bring you discussion of those tests, and present that Pistorius is a physiological impossibility, thanks to his carbon fibre blades.
• Continued coverage of the Tour de France which hits the big mountains on Sunday and Monday. This will include more discussion about the feeding strategies, what riders eat, and the physiology and tactics of the race.

But for today, we look at weight loss (as a prelude to further discussion of this topic, once all the sports news is past):

A hot weight loss tip from the 1930's: Introducing Sylvia-from-Hollywood

So here is a weight loss tip straight out of 1930, which I came across a link from a great blog called Half-Fast, which is worth reading for running humour. The post on narcolepsy is a great read, but spend a while going through the posts if you have time or feel like a laugh. But it was a link to this article on a book from 1930's advocating some truly bizarre methods for weight loss that made me laugh.

It turns out that the 1930's were much like today, with people selling "revolutionary ideas" - all that has changed is the platform and method of communication. The following is an excerpt from a book called "No More Alibis", written by a Sylvia of Hollywood. It seems that Sylvia was something of a Jane Fonda of the 1930's. This is her advice for fat loss:

In case you wondered how this might look, there was a picture:


I guess the less said the better! I have few words to add to Sylvia's description (no, it doesn't work!) Though it would seem that if you squeeze often enough, you develop an upper body like a WWE Superstar!

Innovation and progress: Leading us away from truth

Getting more serious now, the advice above, while laughable, is typical of what you'll find today, in various forms. This post on marketing and weight loss (our first venture into these waters) is inspired by a combination of some of your recent comments, work I did recently here in SA, and then a general theme here at The Science of Sport. Those who've been reading recently will know that we've had some discussion around "innovation" and scientific progress, as applied to things like running technique, training, diet, running shoes, and now weight loss. Our general approach (as scientists and as people) is to be sceptical of anything that is punted as "revolutionary", because the packaging of "revolutions" almost always compromises the facts!

I was then recently asked to give a presentation on "The Science of Weight Loss" here at the Sports Science Institute of SA where I work. In preparing that talk, I got to thinking that when it comes to making a profit, innovation usually leads us further and further away from the truth.

In other words, whenever someone packages and then tries to sell an idea (be it technology and training, technique, shoes, or methods for weight loss), they have to be novel and innovative, in order to stand out among the clutter. When you do a search on Amazon.com for "weight loss", you find 60,000 books in the results! Now, if you're the guy writing book number 60,001, you have to innovate, find a point of differentiation. That is obvious, but the problem is that this innovation often leads us away from truth and into fiction.

Weight loss: We've lost sight of the truth thanks to rampant marketing

Take for example the following article, which was sent to us by Steve (thanks Steve!)

The Cardio-free diet: Optimal method for weight loss?

We'll discuss this concept in more detail at some stage. But briefly, it talks about a revolutionary new method for weight loss, where ZERO cardio training should be done. We won't discuss the merits of the argument here, other than to say that it's a very (very) shaky theory, to say the least. The entire basis for the argument is flawed, and the "evidence" to back up the theory is weak and empty. Truth is, cardio is needed, and is crucial to weight loss success. But remember, Jim Karas wants your money, and why would you pay for something that everyone else is doing?

The same goes for running technique - you'd never pay hundreds of dollars to be told that you should run using common sense principles! But when a technique is packaged and then sold, with someone cashing the cheque on the other end, then you have a market. And that is unfortunately what happens.

I must make clear that this is NOT always the case, and there are some excellent ideas and products. And even the theory is often sound - in the case of running techniques, for example, I think the principles are good, I'd advocate them, but it's the "packaging" and sale of technique as a product that I have issue with, as you'll have seen reading our series on Running technique from start to finish!

Quite where the discerning consumer must go to distinguish between genuine progress in understanding and marketing fad is difficult to know. I guess knowledge is power and insurance, but the fact that these concepts have existed for perhaps 80 years (and more) is evidence that the market will always exist, and people will always try to exploit it.

Weight loss - an unexplored territory

At the risk of committing to yet another topic that we should look into in the future, weight loss is a great topic for physiology, because it provides good context for discussion. So I'm sure we'll pick it up in the future, just don't know when!

Have a great weekend, enjoy The Tour de France and the Golden League athletics from Rome!

Ross

Credit to 15minute lunch for the Sylvia article - also some funny content on his site