Here is a study that looked at resting energy expenditure (REE) under a calorie restricted diet (L C Henson D C Poole C P Donahoe D Heber. Effects of exercise training on resting energy expenditure during caloric restriction. The American Journal of Clinical Nutrition, Volume 46, Issue 6, 1 December 1987, Pages 893–899).
The seven subjects were moderately obese women put on a calorie restricted diet. The test was lasted nine weeks. They were exercised for three weeks at the end of their diet at 70% of their VO2max.
Resting energy expenditure (REE), maximum oxygen uptake (VO2max), and body composition were measured in seven moderately obese women during 9 wk of dietary restriction (800 kcal/d). During weeks 4-6, subjects underwent exercise training (30 min cycling/d, 5 d/wk, at 70% VO2max).
The conclusions were:
The first 3 wk of caloric restriction decreased REE by 13% (from 1437 +/- 76 to 1254 +/- 66 kcal/24 h, means +/- SEM, p less than 0.05).
That shouldn’t be a surprise since weight loss results in a reduction of Energy Expenditure. The numbers need to be compared closely to the actual weight loss to see how much of the reduction in TDEE was from the weight difference and how much was from metabolic adaptation.
How was their performance affected?
Exercise training increased VO2max (from 1717 +/- 108 to 1960 +/- 120 mL/min, means +/- SEM, p less than 0.05)
Their VO2max showed a substantial improvement for only three weeks of training. It would have been interesting to have a control group which was not put on the exercise program to tease out whether some of this was due to weight reduction or it was due to the exercise.
but did not elevate the dietary-depressed REE (from 1254 +/- 66 to 1262 +/- 62 kcal/24 h).
It looks like the REE did show an increase but it was not statistically significant.
The greatest decrease in body fat (3.7 +/- 0.4 kg) occurred during exercise training, resulting in a small apparent increase in REE when expressed per kilogram total body weight. However, expressed per unit lean body mass, REE remained suppressed throughout the period of caloric restriction.
At 70% of VO2max they were at a good rate for loss of both carbohydrates and fat stores. It would be interesting to see their actual rates of substrate metabolism.
We conclude that exercise training of sufficient intensity to substantially increase VO2max does not reverse the dietary-induced depression of REE.
This is interesting since there’s a common assumption that exercising will cause people to burn more calories at rest but that wasn’t the case in this particular situation.
However, the increase in VO2max itself was worthwhile as it indicates a gain in fitness.