One of the most common reasons people increase activity is to burn more calories, create a calorie deficit, and lose weight.
A new study demonstrates that this might not work as simply as we think.
Using the most extensive dataset on human energy expenditure ever assembled ( n = 1754), researchers demonstrated that increasing activity is compensated by a decrease in basal or resting energy expenditure.
So for every 100 calories of additional activity, we only burn 72 calories - a compensation of 28%.
This relationship was similar for men and women, young and old.
Making matters worse for people seeking to lose weight through increased energy expenditure is the observation that the level of compensation increases with weight.
People at the 90th percentile weight (BMI = 33) in this study compensate almost half of their calories.
Finally, there is a significant variation amongst people - some compensate more or less than others.
This finding has several implications:
The potential relationship between the increase in appetite associated with increased activity and this energy compensation was not touched upon in the study but has significant real-world implications.
The increase in appetite (and consumption) for some people may be equal or potentially greater than the increase in actual calories burned.
These combined effects may be why exercise alone generally does not work for significant weight loss.
Another potential implication not touched upon in the study is that the compensatory decrease in energy expenditure may have possible health benefits (i.e. decreased immune system activity, decreasing chronic inflammation).
This may be one reason why exercise has been shown to have such significant health benefits despite its lack of efficacy for weight loss.
Dr. Brendan Byrne