Resting energy expenditure (REE) is the calories you burn while you’re doing nothing. REE is mostly determined by how big you are. So if you lose weight it goes down. But does it go down even more than that? We know that the energy cost of any activity goes down more than would be predicted by weight loss. It also goes down when you “get in shape,” that is get fit by regular exercise. But it has been reported that REE does not over-compensate like that.
Looking at this question was a study reported this month in Obesity, a research journal and the official publication of The Obesity Society (1).
These investigators used data derived from a study they did and reported in The New England Journal of Medicine in 2009.(2)
You will remember that that study showed that on calorie-reduced diets with different compositions of fat, protein and carbohydrate, a group of obese people lost about 7% of their weight at 6 months and if they hung in there, they managed to maintain 4.7% weight loss by the end of 2 years and the different compositions of fat, protein and carbohydrate didn’t matter.
In a substudy of 99 of these subjects they measured total enegry expenditure and found a decrease during weight loss and that decrease was accounted for primarily by the decrease in REE. (3) In this report they further studied the relation of REE to diet and measured again at 6 months and 2 years. At 6 months the REE was lower than predicted on the basis of the weight lost but at 24 months it was back to a little more than predicted on the basis of the weight lost at that point. The declines in REE were less in women than in men and less in older vs younger but again there was no difference between diets.
So in summary, it would seem like your body fights back harder by turning down REE while you’re losing weight but then resumes burning calories simply on the basis of size.
Furthermore, these days there is a lot of excitement about the possibility that a calorie isn’t always a calorie as we’ve mentioned several times in the recent past. But in the long run and where it really matters most - trying to lose weight - these reports fall into the a-calorie-is-a-calorie column.
1. de Jonge L, Bray GA et al. Effect of diet composition and weight loss on resting energy expenditure in the POUNDS LOST study. Obesity 2012;20:2384-89.
2. Sacks FM, Bray GA et al. Comparison of weight-loss diets with different compositions of fat, protein and carbohydrates. N Egl J Med 2009;360:859-73.
3. Bray GA et al. Effect of diet composition on energy expenditure during weight loss. Int J Obes 2012;36:448-55.