The Limits of Exercise
“Oh, I ate that cookie earlier today! I'll just burn it off later at the gym.”
How many times have you or a friend said something like this while trying to lose weight?
So is that true? Is burning off the calories that you eat enough to keep you on track on your weight-loss journey?
There is no question that exercise leads to a healthy lifestyle overall and has been shown to decrease the incidence of a number of health concerns, but is exercise alone enough to make you lose weight?
First let’s talk about the science of weight loss. In order to lose 1 pound of weight you need to create a caloric deficit in (burn more than you eat) of about 3500 calories a day. That sounds simple enough, right?
If you’re maintaining your weight currently (not losing or gaining any weight) then you’re eating the same amount of calories that you burn. In order to lose weight you must either eat less or burn more or some combination of the two. But what if you focus purely on exercise and continue to eat whatever you wanted? Would that bring you closer to your weight loss goals?
Let’s take a look at the three different ways that your body burns what you eat and drink:
Basal metabolic rate or BMR is the amount of energy it takes to keep your body running accounts for about 70% of the calories that you burn in a day. BMR is determined by a number of things, including your genetics, your weight, your age and the amount of muscle mass that you carry. You have little to no control over this besides maybe lifting weights to increase your muscle mass and burn more calories.
Breaking down food or the thermic effect of food accounts for another 10 to 20% of how much your body burns.
Physical activity accounts for the last 10 to 20%.. But physical activity includes two different things; one is formal exercise which is what most people think of when they think of physical activity. This includes things like jogging, running and going to a Zumba class. The other type of physical activity are the things that you do that are not formal exercise, like clean your house, take the stairs etc. In our society, labor reducing technology makes it very difficult to increase both formal and informal exercise activities.
So only between 10 and 20% of what you burn is from formal exercise. You can say, “Well simple, I’ll just workout more and burn more calories.” But even athletes only expend approximately 15% of their calories through formal exercise. So if you focus on exercise, you’re only changing a very small portion of the calories that you burn overall, and only focusing on burning a very small portion of your caloric intake or what you consume. This is compared to changing your diet, which is 100% of the calories that you intake.
Let’s say for instance, you ran 13 miles. A value meal at McDonald’s would easily cancel that out. Most people are not running 13 miles daily. If you ran 3 miles, two cookies might knock you out of your deficit for the day and thus, thwart your hard-earned weight loss efforts.
Furthermore, because the body has a tendency to want to return to your genetic set-point, or the weight at which is most comfortable, your hormones begin to signal hunger the more you exercise. Therefore your ability to reduce temptation is compromised.
Of course I am a huge proponent of exercise, both formal and informal and cardio AND weight training. But I suggest that you change your attitude towards exercise to support healthy weight loss. Do it because it leads to a healthier lifestyle and will help support your weight loss, NOT because you think it will automatically lead to weight loss. Exercise, especially cardio, is a very blunt tool when it comes creating a caloric deficit (weight loss). Changing your nutrition habits is where you will see the most results.