Diet vs. Exercise

It has long been assumed that a lack of physical activity is one reason for the alarming rates of overweight and obesity seen in the United States and other developed countries. According to this theory, our bodies have evolved to be far more active than they are with today’s typical sedentary lifestyle, and therefore the body burns fewer calories than it would with a substantially higher level of physical activity. While it seems reasonable, this explanation has not held up well to scientific scrutiny — including a new study involving people whose lifestyle could not be more different from what is typical in Western countries.


As one of the researchers noted last month in an essay in The New York Times, he and his colleagues decided to examine whether a consistently higher level of physical activity corresponds to a consistently higher number of calories burned by the body. Their subjects were members of the Hadza tribe in Tanzania, a group that lives much the way all humans are believed to have lived before the agricultural revolution began some 12,000 years ago. The Hadza live in grass huts and spend the day gathering food, with the women digging up roots and picking berries while the men hunt with traditional poison-tipped arrows and gather honey. As a separate article in the Times notes, men walk an average of seven and women an average of three miles each day. While this represents significantly more physical activity than the typical American gets, and the Hadza burn just as many calories through exercise as would be expected, their overall energy expenditure — the number of calories burned — is no greater than what is typically seen in more sedentary people. (Overall energy expenditure was measured through a sophisticated type of urine analysis.)

As the second Times article notes, this finding is actually consistent with weight-loss studies that have been carried out in the United States. Contrary to popular belief — or at least popular hope — exercise doesn’t raise the metabolic rate of most people when they’re not exercising and can, in fact, actually slow it down. According to the Hadza researcher, this may be because our bodies have evolved to keep energy expenditure as consistent as possible. Since lack of food rather than overabundance of it has been a greater problem throughout most of human history, it makes sense that the body would not want to burn extra calories in the face of increased physical activity — especially since that activity may be necessary to get the food in the first place, as in cases of hunting and foraging. This stasis in energy expenditure supports the idea that the Western diet is more responsible for overweight and obesity than is a sedentary lifestyle.

And yet most weight-loss experts, even when they consider that overall energy expenditure does not necessarily increase with more physical activity, recommend exercise as part of a weight-loss program. This invites speculation that physical activity may have benefits that are distinct from its direct effect on calories burned, such as helping to regulate hunger. And, of course, exercise does burn a greater number of calories while it is being performed, so getting a very large amount of it will almost certainly lead to more calories being burned overall.

What do you think — in your experience, does your diet or level of physical activity seem to have a greater effect on your weight? Is it reasonable to expect people in modern societies to have the same activity level, or to follow the same diet, as hunter-gatherers? Do you feel like your body wants more physical activity, or is it a struggle to motivate yourself to exercise? Do you feel it would be easier for you to get more exercise, or to change your diet? Leave a comment below!

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  • joan

    My first thought is that because of a mixed DNA for most of us, we inherit some factors that contribute to lifestyle, including choice of food items!

    Perhaps I am a hunter-gatherer in one sense….have home-grown strawberries, pick wild berries, fresh fish twice a week, gather nuts and wild berries, pick up kelp, sea lettuce, mussels from the ocean. – and use some products from the super market but mostly from health food stores. I have a combination of the new and the old cultural behaviors that work for me.

    Today there may be far fewer hunter-gathers. On average, I believe it is a mixed bag of lifestyles within any society.

    My meal plans are carefully chosen to enjoy my favorite foods and recipes prepared without the junk ingredients found in most packaged foods today.

    My choice of meals and exercise does help me to maintain a healthy lifestyle. It is easier for me to watch both meal planning and exercise; a great combination to enjoy life

    There is nothing more satisfying and helpful to us as diabetics than to practice moderation within our lifestyle.

  • Steve

    As a diabetic, dieting has a more immediate effect on my weight but exercise in conjunction with dieting has been more effective in the long run. I do not think it is reasonable to expect people in modern society to have the same activity or same diet as hunter-gatherers but most of us do not even do what IS reasonable.
    I feel my body wants more physical activity and yes it is a struggle to motivate myself to do more. I find it easier to change my diet.

    I find it easier to motivate myself to exercise if I do some task that becomes exercise, such as yard work, walking behind a mower or other tasks that need to be done anyway. While this may not be high impact, it can be very beneficial long term. If you think about our society, we drive miles to the gym to walk a mile or two on a treadmill or track. The hunter-gatherers get their exercise in the process of gathering food for survival. The convenience of living in modern society can be a inconvenience to our health.

    Now, let me hit the enter button and exercise my finger…instead of walking to a mailbox and mailing this comment in. LOL

  • jim snell

    Articles such as this do nothing but sow confusion in the diabetic type 2 population.

    In fact I suggest assinine.

    Fact remeains that in order to store fat one needs excess glucose in arteries/veins for cells to have opportunity to store as fat.

    If the exercise done does not lower levels much in the temporary stores of the skeletal muscle cells, then in fact there will be no reliable reduction of weight.

    Once one exercises sufficiently to force skeletal muscle cells temporary glucose storage to go low enough and draw down the glucose in blood stream, one can than have opportunity to burn off excess weight.

    I found this out and in fact made my diabetes worse till I understood the need to exercise sufficiently, cut back liver leakage on metformin and drop diet to 1200 caloroes.

    Self serving studies like tis are totally unhelpful and only prompt continuing body rot out
    in type 2 diabetes.

    Energy balance equations still properly apply and once body hauled back to energy balance by fixing all pertinent issues, then the weight gain and rot are stopped.

    Stupid studies like this are ridiculous and only justify rotting ones body out and doing nothing.

  • al

    Diet has a greater affect on weight ,but the extra muscle helps.

  • Fred

    You just finished explaining how a study shows that men who walk 7 miles a day gathering food have the same overall energy expenditure as post industrial society members, and one that disproves the notion of exercise and metabolic rate, and then say “And, of course, exercise does burn a greater number of calories while it is being performed, so getting a very large amount of it will almost certainly lead to more calories being burned overall.”

    This shows just how deeply embedded the repeatedly scientifically disproved notion of the diet/exercise calories in/out formula is because it fits with our cultural notions of self-deprivation and guilt. You can actually be writing about one of the studies that disprove it, and then repeat it in the next paragraph.

    We have a lot to learn about the metabolic and endocrine systems and we need to follow the science without projecting beliefs on it. Only then will find solutions that work.

  • Sally

    I would agree its largely diet related. Since approaching my mid-40s, I have suddenly had a massive slow down and am constantly fatigued – yet I cycle for an hour (25km) a day as I force myself – its my commute to and from work! – and will regularly walk for between 5 and 10km on the weekends. Despite this exercise, I am always fatigued by days end, get puffed walking up a gentle incline and I have honest-to-goodness not lost a single kilogram of weight as a result of this introduction of regular exercise into my life.

    I know initially some of my exercise exhaustion was overdoing it (not getting any younger!) but since then I’ve built my cycling up from 3 days/week to 5 days/week and maintained that for about 18 months now, I seem to have hit a plateau where I am still tired and not loosing any weight or able to walk up a gentle incline.

    Maybe when I was in my 20s I got away with eating anything, but now that I’m in my 40s I am fairly convinced my diet is too carb/processed-centric and I need to back off and eat more raw foods!
    And I am also rather firmly convinced that you plateau when exercising, just like the Hadza Tribe. I console myself that as long as I don’t increase calorie input, my cycling seems to keep me at the same weight – but I’m certainly not loosing it like the experts say!

  • Veronica

    For me the two options are very important! I love walking and try to avoid harmful foods! I stay in good weight!