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Saturday, January 16, 2010

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!



McTofu said...

Loving this series on weight loss, exercise and the move more, eat less equation. I have in the last year used this equation to great effect [having lost 26lbs so far] and will continue to use it to lose a further 42lbs [to get me down to an optimum healthy weight]. I have started a blog to track my progress and investigate the vast world of diet and fitness, so find The Science of Sport really helpful, thanks guys! Incidentally, I grew up in SA and was hugely active in those years but a return to the UK and lack of sunshine has been my fitness downfall. I'm back on it though and with your great advice, I'm certain I can get back to fit and healthy!!

arthur said...

I think that, actually, quantity is not the only thing that matters, but quality as well.

Is 10 calories from fat really the same 10 calories from protein and really the same 10 calories from sugar?

"Many people think weight loss is simply about cutting calories. But context counts here, too. Calories do have context and that’s what I want to explore today. Is a calorie from fat the same as a calorie from protein or carbohydrate? Depends on the context..........."

Read on.


George Beinhorn said...

Great stuff, but weight-loss if further complicated by the fact - which I've experienced now for five years - that high-nutrient-density foods, high-bulk (salad, nuts, steamed greens, fruit, etc.) absolutely kill hunger. Joel Fuhrman basis his diet on this notion, and it does work (though I disagree with Fuhrman's stringent line on "bad" fats, including eggs and dairy). A new dietary pyramid, with starchy carbs in lowest priority and smallest amounts, does work.

vikram said...

Great post once again. A quick note, while you mention all this about counting intake and exercise calories, there does not seem to be a mention about the body's inherent ability to maintain a balance. Simply dialing into the body tells one when the balance is reached - (that aha, I'm full vs aha, I love the taste of this but will keep on eating ignoring what my tummy tells me feeling). Why the increase in obsession with counting vs ignoring the bodies natural abilities to keep that balance ?


Ron Wolf said...

It is so important to keep things simple. As you observe, there are many subtle details. In my observation, that's where things go off track for most, they get lost in the details (fats, carbs, timing, fads, etc) and loose track of the cals in. And I think it will be a very big challenge for you, in this series to keep it simple.

I sometimes feel like I'm neurotic about diet - my friends would agree. Yet, the simple fact is that us average folks need to pay nearly constant attention to diet if we want to manage weight. Why? Because the balance is so delicate. As I like to think about it, my daily intake needs to stay within plus or minus two pieces of bread a day of my target intake. Two pieces too many I gain. Two too few I lose. That's not much room for error. Seems neurotic, but that's really the way it is as you point out with your sip of coke example.

Also, careful there with the cals out part. Most of us average athletes can't even come close to 1,000 cals and hour output. We just aren't fit enough. So by dropping figures like 1,500 cals an hour out, you are slipping into elite athlete territory.

OK, I'll bite, is "Arousal" what I think it is?

Michelle Simmons said...

Will you address the issue of age at some point in this weight loss series? I'm only 35, but recently have noted a major difference in my ability to drop a couple pounds. I'm not overweight, and I understand the calories in vs calories out, though I do think my body was more forgiving when I was younger. Is this a real phenomenon or am I just imagining it?
Thanks! Great info here.

jathma said...

Thanks for this series, guys. I am enjoying it.

I am going to respectfully differ with your opinion on counting food and exercise calories to balance the input-output equation.

I run about 3 marathons a year, so am constantly training for a race. I was packing a little extra weight a year or so ago and decided to try to lose 5 lbs.: not an easy task amidst high mileage training. The only way I've been able to both lose weight and maintain an intense workout schedule is by carefully tracking my calories.

The benefits have been, as you state, to understand better the nutritional breakdown of the foods I eat. I think it goes a lot further than that. I know that my estimates for input and output are not accurate, but the data I collect is one (inexpensive) way for me to make a connection between how my body responds (energy levels and weight) when I eat X and burn Y number of calories. I have gotten a pretty good idea of what my net average daily calorie need is to maintain my current weight. Of course, then it's easy to develop a sensible reduction in food intake to achieve weight loss.

Letting nature tell me when to eat, as vikram suggests, hasn't worked for me since often times, in order to take in enough calories, I have to eat when I'm not hungry. Having a tally of my day's intake helps with meal planning and ensures I don't go into an unsustainable deficit situation which is deadly for endurance athletes.

I successfully lost 5 lbs. using this method and knocked 5 minutes off of my marathon PR in the process. It takes a lot of dedication, to be sure, but it does work.

donncha said...

re: your 'devolution of weight loss' book idea, have a read of "The Diet Delusion" by Gary Taubes. Covers the last 100 years of research into diet, and the associated dietary norms/recommendation, with copious references to relevant research on the topic. It's a long book, but bloody interesting and v. well researched.

Simon M said...

Calories in vs calories out doesn't work for weight loss and not just because of the practical difficulties.

As *arthur* points out in pointing to Mark Sissons' blog, calories are NOT equal - a calorie from protein, carb or fat is processed differently and has a different metabolic cost. As Mark says - the context is everything. The "calorie is a calorie" idea is really out of date scientifically.

Some of the most startling research has shown that even the amount and balance of bacteria in your gut effects how many calories you get from food; without the "right" sort you won't get as many calories from carbohydrates as you could. ("Rodents raised in a sterile environment and lacking in gut flora need to eat 30% more calories just to remain the same weight as their normal counterparts. http://en.wikipedia.org/wiki/Gut_flora)
And that's just one example of why the calories in/calories out "balance" theory of weight management is dead in the water.

elodie said...

To further complicate the calorie-counting exercise, there's some doubt as to how accurate food labels are. The method of cooking can affect how many calories are available for absorption. For some foods, cooking makes more calories available, whereas for others, calories are essentially 'burned' in the cooking. Food product manufacturers (as well as home cooks) simply sum up the calories from all of the ingredients, but what's available to the body in digestion often differs from this number by as much as 25%.

Thom said...

One of the best benefits of competitive cycling is that I can eat a lot of great food and still lose weight! But I do have to pay attention. What works for me is to consistently stop eating when I'm full instead of waiting until I'm stuffed. Cut out most if not all of the sugary snacks, which has benefits beyond merely losing weight. Also, I try to lose weight during the off-season when performance is not critical, so I can afford to be a little underpowered. And lastly, doing a short session before bed and not eating afterwards has been effective as of late.

Anonymous said...

Ok, if we are going to swap anecdotes, how about this then? My experience over forty five years of running competitively and training very hard for months at a time for races from 1500m to the marathon is that my appetite almost completely disappeared, to the point where I was having to force myself to eat a nutritious, balanced diet to keep up my daily energy intake sufficiently for the next training session.

I still have a minimal appetite compared to all the non-athletes I know, especially females such as my wife and daughter, most of who seem unable to go for more than a few hours without announcing that they are starving hungry and have to eat again! By contrast, it's only when I start to eat and stimulate my appetite that I ever feel hungry. I've tried testing this theory on and off over the years and have found indeed that I can easily eat just a few times a week without any apparent ill-effects in the short term, other than my ability to train quite as hard or for so long, particularly the day following a hard training session.

I have also found that I tend to glut on beer, wine or whisky, eat volumes of mature cheddar, wolf down chocolate etc, when I'm not training for some worthwhile goal because, frankly, I'm so bored, I lack a stimulus and I need something to help fill the vacuum of my miserable, worthless existence! (Writing only goes so far – one ought to pray for a healthy mind in a healthy body (Orandum est ut sit mens sana in corpore sano [Juvenal])

The final point I would make is that when, many decades ago, I played rugby competitively, my playing mass was almost twenty kilos heavier than my optimal racing mass. Being light is essential for hard training and running fast. The heavier you are the more injuries you get when you train, the lower the quantity, the quality and the maintainable frequency of your training, and the slower you are when you race.

Having the extra body mass and concomitant inertia and momentum, however, is also equally essential, up to a point, when bursting through a tackle or knocking back a large, heavy opponent in a very hard, head on tackle at thigh level, at which I excelled despite my relatively small size, when they’re about to cross the touch line.

MJ said...

Good stuff guys. I've got one more thing to add to the difficulty in counting calories expanded.

Not sure if you read any of Rosenbaum's work, but he has a series of nice studies indicating an alteration in work efficiency present only at low levels (10-25W) after subjects lose 10% of their BW. The opposite is true with a gain in 10%. They have "rescued" this gain in efficiency by giving exogenous in the 10% loss group. Similar efficiency alterations have been seen with a rat weight cyling model by Paul Mclean's group.

To me it strongly suggests that this new set point will be hard to maintain if you only relay on food restriction and daily ambulatory activity. Exercise, where the efficiency no longer exists, would be essential to a maintenance or further weight loss.

Ray said...

Regarding calorie counting, I've always seen two problems:
- Doesn't "poo" contain any calories? If you are counting calories, shouldn't your accounting be complete?
- I recently read that the calories listed on food (in the US anyway), can be off by as much as 20%, without really violating any FDA accuracy guidelines. In restaurants, it can be as much as 50%, as they may add ingredients and sauces, or worse, side dishes, which often don't get counted in "low-cal" offers.

There is a thing, it probably has another name, but I call it "hibernation mode". If you restrict yourself to a low calorie diet, your body slows down its metabolism, going into "hibernation mode", because food is scarce. Your body is fighting against the desired effect. Any simple equation somehow needs to include change in daily metabolism.

Mel said...

Dieting is much more complex than calories in vs. calories out. As a dietitian, I see every day how hormonal and biochemical differences play in to weight loss. On the simpler side of things, most people, athletes included, make the mistake of "backloading" calories. The person eating 2,000 calories with the majority being consumed in the front half of the day during breakfast and multiple snacks will be able to perform better athletically and stay trim. The same person eating 2,000 calories with a light or no breakfast, light lunch, and limited snacking will eat the majority of their calories in the evening and inherently gain weight. Eat during the day, diet at night - flip your day around and lose a few & run/swim/cycle faster and stronger!

Ross Tucker and Jonathan Dugas said...

Hi Melissa

Thanks for the comment. You may not have seen the post AFTEr this one, where I discuss the complexities of calories in vs calories out further, and the biochemical and hormonal aspects of weight management.

I agree 100% with you, but I would argue that these factors, the metabolic changes (like leptin, for example) that affect this balance still apply to the same principle, it is just that the application is made infinitely more complex as a result. If we could manage that complexity, then of course the equation would still apply. So to me, the principle is sound, but its application is difficult, if not impossible.

The latest post hopefully covers some aspects of that.

As for the point about backloading, that's a really good point, thank you!


Farhad Kapadia said...

""The "calorie is a calorie" idea is really out of date scientifically.""

Not really. The calorie or KiloCal or Joule is a simple unit of measureof energy: 1 calorie= the ammount of heat energy needed to raise the temp of 1 ml of water by 1 degre C. One could equally scientifically accurately say that a kg is a kg, or a mile is a mile or a ml is an ml.

What is out of date scientifically is when one makes extrapolations from this basic measure like "a slice of bread has 50 Cal" or "a 1 hour run burns 750 Cal".

Radical Running said...

Thanks Ross and Jonathan for analyzing this topic.

Your observations about awareness are bang on. I blogged my experience with weight loss.

Can't wait to read the whole series.

Duff said...

Hey my advanced exercise physiology class has a specific question about The calorie conundrum: In vs. Out. Directly in the text:
"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."

Will you please show the references and support for this statement, we would love to study this topic further. Thank you very much.