If you’re perplexed by the information above, don’t worry. There’s a simple explanation behind it, which we’ll break up into two parts.
Reason 1. Calorie expenditure through exercise is relatively small in the grand scheme of things.
In order to see why exercise-focused weight loss programs might yield low efficacy, it’s important to understand the accounting behind our daily caloric expenditure.
We spend most of our calories every day just “staying alive.” This is known as our “resting metabolic rate.” The Katch-McArdle formula, which takes into account one’s body fat percentage, is the most accurate way to calculate this number, which is equivalent to:
9.81 x your amount of non-fat mass + 370 calories per day
Let’s say you are a 200 pound man who is at 30% body fat. You expend 1,743 calories per day just staying alive. (200 x (1-.30) * 9.81 + 370 calories)
He’ll expend about 10% on top of that by what’s known as the Thermic Effect of Food (TEF): the amount of calories that he spends digesting and absorbing his dietary intake.
Add another 10% on top of that through a metabolic process known as NEAT ( Non Exercise Adaptive Thermogenesis). This is the amount of calories wasted through things such as fidgeting. Unfortunately, this can vary greatly from individual to individual.
This means that without so much as getting out of bed, our subject has already expended 2,100 calories.
Now, add another 10% for getting out of bed and going about his daily routine and he’s already burned 2,300 calories.
Adding exercise into the equation barely makes a dent in his overall caloric expenditure; most of the work is done before he puts on his running shoes. Now I am not saying that you shouldn’t exercise, but rather, it’s important to realize where a majority of your caloric expenditure is coming from. You wouldn’t take up a paper route in order to supplement a 100k/year salary, would you?
Reason 2. People are horrible estimators of calories in vs. calories out.
Take a look at another study, this one in the Journal of Sports Medicine and Physical Fitness, in which researchers asked the subjects to exercise, estimate their caloric expenditure, and then took them to a buffet afterwards. Subjects were asked to consume the amount of food that they believed they burned in calories. (Sidenote: Where can I sign up for one of these?)
The subjects ended up eating 2-3 times the amount of calories that they burned.
The takeaway from all of this information is that calorie expenditure doesn’t count for much, and human beings are generally terrible at estimating both expenditure and intake.