Drop in resting energy expenditure with weight loss

The Study

There is evidence that after weight loss, resting energy expenditure (REE) drops to levels lower than predicted. This is a major reason why so many people quickly regain lost weight. In this case-control study, three different groups of subjects had their resting energy expenditure measured. The first group included 34 subjects that had lost over 30 lbs. and kept the weight off for 1 year. The second group included 35 normal weight subjects. The third group included 33 overweight and obese subjects. Resting energy expenditure was predicted by standardized formulas and then precisely measured with indirect calorimetry. There were several interesting results:

-In the subjects that lost at least 30 lbs., there was no significant difference between predicted and measured resting energy expenditure.

-However, in the 34 subjects that had lost over 30 lbs. and kept it off for a year, there was a lot of variability. When comparing the expected to the actual resting energy expenditure, the range was -257 to +163 calories per day.

-In the weight loss maintainers, a lower than predicted REE was positively correlated with maximum weight, maximum BMI and maximum weight lost. American Journal of Clinical Nutrition 2018; 108:658-66.

Take Home Message

There are 3 really interesting things about this study:

1) The more weight that a subject had to lose, the more severe the reduction in resting energy expenditure. This supports the idea that the more weight you lose, the harder it is to keep it off.

2) Even though these subjects lost a lot of weight, their REE did not drop all that much from what would be expected given their new weight. This is somewhat surprising given previous results.

3) There was a lot of variability in resting energy expenditure after weight loss. The range was 257 calories per day lower than expected to 163 calories higher than expected. It is encouraging that even subjects who had a serious drop in REE were able to maintain their weight loss for over a year. It has been previously argued that a drop in REE makes it impossible to keep lost weight off.

The REE response to weight loss is a fascinating topic that we need to learn more about in order to increase weight loss success. The fact that it varies so much at the individual level is a new concept to me.  Is this because of exercise habits, genetics or something else? We’ll have to stay tuned as further research evolves on this topic.