If you’d asked me a decade ago what was the best method of weight loss was if I could choose only exercise or diet, I would have said exercise all day. That is, increase exercise, lean body mass, and so forth, to create a caloric deficit vs reducing calories if I could only choose one of those two approaches. That conclusion appears to have been wrong, and I’m here to explain why. On the surface, that conclusion turns a sacred cow of the fitness world on its head, but in retrospect, I think we knew it all along. Hey, someone said “you can’t out exercise a bad diet” and that’s essentially true. Who ever said it, just didn’t realize just how true it is.
We all know those people who are consistent in the gym and actually do work hard at it, yet look essentially the same year after year in terms of their bodyfat levels, and it’s not until they really get their act together on the nutritional side, do they see real changes in body composition. End of the day, exercise, regardless of type, is just not as important as once thought it was for weight loss. Will some use that as an excuse not to exercise? Sadly, yes. But those types are usually looking for excuses not to exercise anyway, so they’re not going to change in that respect. The rest of us realize regular exercise has so many benefits to general health, well-being, disease prevention, cardio vascular health, mood, anti-aging, how we look, and so forth, this news really changes nothing for us.
Like it or not however, exercise, regardless of the type, is just not a major contributor to weight loss. Understandably, many in the fitness community have rejected that idea (I was one of them until the data became simply overwhelming) as it causes some cognitive dissonance* in them, and or other reasons to reject it, such as a a perceived loss of revenue perhaps.
“Exercise is not a major contributor to weight loss? Madness!” they will say.
Unfortunately, that’s the fact of the matter, and whether I/we like it, science don’t care… Bottom line: A reduction in calorie via dietary changes is far more effective for weight loss then any attempts to increase either volume or intensity of exercise to lose weight. Obviously, the combination of both – dietary changes and exercise – is going to be the most effective, but the exercise component contributes much less to that caloric deficit than we thought. Yet again, the human body is able to outsmart us as it relates to efficiently dealing with total energy flux. In a nut shell, exercise itself does not use as many calories as we thought, added muscle mass does not require as many calories as we thought to sustain itself (approx. 6-9 cals per lb of LBM), and the post workout calorie expenditure (via EPOC), you guessed it, does not contribute a great deal to energy expenditure. All of them combined contributes to TDEE, but it’s not nearly as substantial as was assumed. I know, some will view that as an attack on exercise by scrawny researchers and aerobic weenies, and dad bod lovers, but it’s not. The fact is It’s actually difficult to create a sustained calorie deficit by exercise alone to see meaningful weight loss in the form of bodyfat, unless you’re running marathons regularly, or involved in Iron Man competitions and such, and the reality is, that’s not sustainable long term, the effect does plateau, which I will discuss shortly.
I’m not going to throw a bunch of numbers out regarding the above, as they continue to be something of a moving target, but the general conclusion is the same and well supported by a multitude of different directions; the major variable we all thought was the “key” to weight loss at it related to exercise, as outlined above, don’t contribute all that much to our total daily energy expenditure (TDEE) we’d all thought. File under shit happens.
Amazingly, some studies find exercise may actually undermine weight loss in some, as they tend to simply eat more, often due to the effects of exercise on appetite as well as assuming they “burned” far more calories than they actually did during their workout and other factors, some subtle, some not. For example, studies find some people actually move less via NEAT (non-exercise activity thermogenesis or non-exercise activity energy expenditure) during the day once they start exercising regularly, partially or fully offsetting the calories used during their workouts. That’s not an excuse to not exercise while attempting to lose some bodyfat, but it’s a reason why one must pay strict attention to the nutritional aspect of their efforts to see real results in bodyfat. If you think about it, it does make intuitive sense, even if the reality that exercise is not all it was cracked up to be as it applies to weight loss will come as a shock to so many. OK, take a breath and think about it for a few minutes. While exercise is not a great weight loss drug, I think obesity researcher, Yoni Freedhoff summarized it well in an article via VOX magazine:
Make smart food choices!
“By preventing cancers, improving blood pressure, cholesterol and sugar, bolstering sleep, attention, energy and mood, and doing so much more, exercise has indisputably proven itself to be the world’s best drug – better than any pharmaceutical product any physician could ever prescribe. Sadly though, exercise is not a weight loss drug, and so long as we continue to push exercise primarily (and sadly sometimes exclusively) in the name of preventing or treating adult or childhood obesity, we’ll also continue to short-change the public about the genuinely incredible health benefits of exercise, and simultaneously misinform them about the realities of long term weight management.”
Enter The Constrained Total Energy Expenditure hypothesis
The human body is incredibly adaptable to differences in energy and energy output, and the total energy expenditure (TEE) not a wide as people might think between say couch potatoes and those digging ditches all day or running marathons and such. In fact, those who exercise regularly do not have a markedly different TEE then those who do not, leading researchers to conclude the human body actively modulates metabolism to adjust to energy flux from increased or decreased activity levels and or caloric intakes. Most people will assume “more is better” when it comes to exercise and “burning” calories, but it appears the human body actually keeps a fairly tight control of that by various mechanisms, some not yet fully elucidated. (1) That is, the body “constrains” how many calories are used via metabolic adaptations and more does not appear to actually be better as far as exercise is concerned. For those who want to get into the details, I highly recommend reading the full report Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans in Volume 26, Issue 3, 8 February 2016, Pages 410-417 of Journal home page for Current Biology. A less dense discussion of that study and related matters, is “Constrained Energy Expenditures and Not Outrunning Our Forks” and “Why you won’t lose weight with exercise alone” as two excellent reads.
There’s a lot under the hood in this discussion and plenty of confounding variables to all this, but the take home is pretty straight forward: exercise is not a major factor to weight loss that many assumed in decades past, the human body proves itself to be far more adaptable to maintaining homeostasis than we realized, and when it comes to weight loss, “you can’t out exercise a bad diet” to paraphrase who ever said that originally. If weight loss is the goal, the major focus should be on creating the caloric deficit by nutrition, with exercise perhaps adding and additional 10% to that deficit, and good things will happen.
Finally, you still have to exercise for all the reasons covered above, and thus, it’s moot as to whether these findings actually change anything for health conscious individuals. A decade ago I would have said weight loss without regular exercise is going to result in failure to lose weight. While exercise will assist to be sure – as every little bit helps – it’s not the weight loss panacea once assumed. Hey, don’t kill the messenger. Now get in the gym and healthy up!
(1) Exercise: Is More Always Better? Journal home page for Current Biology.Volume 26, Issue 3, 8 February 2016, Pages R102-R104