Monday, July 30, 2012

Weight is Food. Health is Fitness.

A fascinating albeit small study out of PLoS ONE adds to my personal confirmation bias that the driving force behind societal weight gain isn't a decrease in burnt calories, but rather an increase in consumed ones.

Now to date we've seen doubly labeled water studies (our current gold standard in measuring total daily caloric expenditures) which have demonstrated that we're not burning any fewer calories now than we did in the early 1980s, and that we city folks living in North American luxury burn just as many daily calories as folks living in developing nations.

Here the authors took things one step further back into human history and using doubly labeled water they measured the energy expenditure of 30 Hadza foragers - a hunter gatherer society that live in a savannah-woodland area in Tanzania (that's a few Hadza up above).

According to the authors,
"the Hadza hunt and gather on foot with bows, small axes, and digging sticks, without the aid of modern tools or equipment"
The authors hypothesized that if a lack of physical activity were responsible for the rapid rise in global obesity, that the Hadza's lifestyles ought to burn a great many more calories than ours.

Not surprisingly the Hadza were found to be highly physically active and quite lean (their average BMI was reported as roughly 20). But what about their daily burns?  The authors found that energy expenditure among both Hadza men and women did not differ from those of men and women living in our modern day utopia.

The authors report too that their multivariate analyses confirm that the lack of difference is independent of weight (meaning that the increased calories associated with simply carrying heavier weights here in North America don't account for the equivalency of findings) and body composition differences (lean and fat mass).

Interestingly too the authors did not find any correlation between total daily Hadza walking and their total energy expenditures meaning that regardless of how many kilometres they walked daily, they burned roughly the same number of calories.

All of these findings led the authors to hypothesize,
"that TEE may be a relatively stable, constrained physiological trait for the human species, more a product of our common genetic inheritance than our diverse lifestyles"

We haven't slowed down at all over the course of these past 50 years and perhaps not since the Pleistocene era which lasted from roughly 2.5 million to 11,700 years ago.

Further translation?

If we haven't slowed down in 11,700 years and yet our weights have risen dramatically the only other possibility, and it's the one I subscribe to, is that we're eating a lot more than we used to.

But please don't read this piece and think that exercise isn't important. Instead read it and recognize that while your weight may be primarily determined by what you eat, there's likely nothing more beneficial to your health than regular exercise. The gym may not make you slim, but study after study after study reports that it will keep you living longer, and living better - and those outcomes are far more important to your quality and quantity of life than what your stupid scale might tell you in the morning.

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  1. Darius Szpilewski7:06 am

    While I believe increased physical activity coexisting with over-consumption of calories will not prevent weight gain, I do believe proper training (not walking) plays crucial role in weight loss. Not because of calories it burns, but because of physical and physiological (and perhaps mental/emotional) adaptations.

    1. John U4:44 pm

      Why do you believe that? Is this just your feeling or is there some science behind it?

  2. I'm unconvinced by the constant evocation of 11,700 years.

    The time-frame does contain the digits 1,7 & 0 but just look back 170 years to Europe & North America in the 1840's.


  3. Anonymous7:18 am

    I purchased a heart rate monitor a while ago & was really surprised by how few calories are burned during exercise. I still exercise of course, but I do it with the mindset that it's good for my overall health and not necessarily the way to lose weight. I guess the old saying is true - weight loss is 90% what we eat and 10% exercise.

  4. Anonymous7:54 am

    It seems the study touches on this, but I wonder if you could explain a little bit how the study takes into account lean body makeup (like maybe traditional socities don't do any more "work" over the course of the day, but have more muscle and thus burn more calories regardless).

  5. I love this article. I am so tired of everyone posting how many calories the burned and using it as an excuse to eat more. I didn't manage to lose weight until I added exercise and increased activity in my life - but I firmly believe this worked because by doing that I shifted my social focus from social eating events (movies, dinners, coffee shops) to more activity-oriented social events (hiking, river walks, bike trips, swimming, exercises classes). It's nice to see "back-up" for my beliefs, as it gives me strength to believe I can maintain this change.

    1. Ah, that sums it up, Deborah! Perfect!

  6. I would say I agree that first calorie control is the contributor to weight gain. To combat this I think people can benefit from a food journal where they record everything they eat along with its nutrient composition (it really helps open your eyes to how your eating!)

  7. Can always count on you to post about the newest, most relevant studies, Yoni! :)

  8. I agree; food choices are paramount. I am a physician who lost 125 lbs over ~18 months and have maintained that weight loss for 2.5 years now.
    I believe simple carbs cause us (and used to cause me) to eat more later. I also believe there are important distinction between aerobic exercise and resistance/weight training. Both types of exercise have been crucial to my weight loss and maintenance, though I believe food choices account for 2/3 of weight loss.

  9. I think the important question is - why are we eating more calories.

  10. Anonymous2:44 pm

    fyi, typo in paragraph three. "hunger gatherer" I think should be "hunter gatherer"

  11. As a trainer, I've always said to my clients that they should never count exercise calories towards their daily food intake of calories. Exercise and forget it is my motto!

  12. Late to the party but I have a question. Did they also then compare calorie consumption? It seems like a fairly easy measure and would provide the most convincing evidence right?