The science is in: exercise won’t help you lose much weight.
We’ve been conditioned to think of exercise as a key ingredient – perhaps the most important ingredient for weight loss effort. You know the drill: Join the gym on January 1 if you want to reach your New Year’s resolution for weight loss. But in truth, the evidence has been accumulating for years that exercise, while great for health and the energy used, isn’t actually all that important for weight loss.
To learn more about why, I read through more than 60 studies (including high-quality, systematic reviews of all the best-available research) on exercise and weight loss for a recent installment of Show Me The Evidence. Here’s a quick summary of what I learned.
Exercise accounts for a small portion of daily calorie burn
One very underappreciated fact about exercise is that even when you work out, the extra calories you burn only account for a small part of the energy used even with physical activity.
There are four main components to energy expenditure, 1) basal metabolic rate, or the energy used for basic functioning when the body is at rest; 2) the energy used to break down food; and 3) the energy used in physical activity 4) the energy used in stressful situations.
What’s important to absorb is the fact that we have very little control over our basal metabolic rate, but it’s actually our biggest energy hog. “It’s generally accepted that for most people, the basal metabolic rate accounts for 60 to 80 percent of total energy expenditure. Digesting food accounts for about 10 percent. So the basal metabolic rate is the key player in the energy department.
That leaves only 10 to 30 percent for physical activity, of which exercise is only a subset. (Remember, physical activity includes all movement, including walking around, fidgeting, et cetera.) The energy used in all those physical activities counts.
The implication here is that while your food intake accounts for 100 percent of the energy that goes into your body, exercise only burns off less than 10 to 30 percent of it. Well physical activity and the energy used with a proper diet for weight loss will help your basal metabolic rate which will still speed up your results for weight loss.
It’s hard to create a significant calorie deficit through exercise
Using the National Institutes of Health’s Body Weight Planner — which gives a more realistic estimation on physical activity for weight loss than the old 3,500 calorie rule — mathematician Kevin Hall created this model to show why adding a regular exercise program is unlikely to lead to significant weight loss. With physical activity you need a diet plan that will speed up your basal metabolic rate.
If a hypothetical 200-pound man added 60 minutes of medium-intensity running four days per week while keeping his calorie intake the same, and he did this for 30 days, he’d lose five pounds. “If this person decided to increase food intake or relax more to recover from the added exercise, then even less weight would be lost. Exercise is a great way to help in weight loss but only with a common sense approach.(Good Nutrition:)
So if one is overweight or obese, and presumably trying to lose dozens of pounds, it would take an incredible amount of time, will, and effort to make a real impact through exercise alone. The energy used in physical activity has to initiate a clean healthy diet to get quick results.
Exercise can undermine weight loss in other, subtle ways
How much we eat is connected to how much exercise we do. When we move more, we sometimes eat more too, or eat less when we don’t exercise.
One 2009 study shows that people seemed to increase their food intake after exercise — either because they thought they burned off a lot of calories or because they were hungrier. Another review of studies from 2012 found that people generally overestimated how much energy exercise burned for weight loss and the energy used made them eat more.
“You exercise on that machine for an hour, and that work can be erased with five minutes of eating afterward,” Hall says. A single slice of pizza, for example, could undo the benefit of an hour’s workout. So could a cafe mocha or an ice cream cone. The energy you put into your physical activity will have no effect for weight loss with a horrible diet like that.
There’s also evidence to suggest that some people simply slow down after a workout, using less energy on their non-gym activities. They might decide to lie down for a rest, fidget less because they’re tired, or take the elevator instead of the stairs.
We need to reframe how we think about exercise
Obesity doctor Yoni Freedhoff has called for a rebranding of how we think of exercise. Exercise has staggering benefits — it just may not help much in the quest for weight loss (Remember the basal metabolic rate) Exercise is a great health benefit you just have to dial in a nutritious diet for weight loss and the energy used in combination will have the desired effect.
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. Exercise is not a weight loss drug, and so long as we continue to push exercise primarily (and sadly sometimes exclusively) for weight loss without a sound diet, 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.
The evidence is now clear: Exercise is excellent for health; it’s just not that important for weight loss. So don’t expect to lose a lot of weight by ramping up physical activity alone. The energy used for physical activity has to incorporate a clean lifestyle for weight loss.
As a society, we also need to stop treating a lack of exercise and diet as equally responsible for the obesity problem in this country. Public-health obesity policies should prioritize fighting the over-consumption of low-quality food and improving the food environment, but money is money and fast food is a billion dollar industry. As a licensed nutrition guru there is nothing healthier than a nutritious diet for energy and physical activity.