1. The oxygen utilization of ten women was measured after consuming meals supplying 230–1200 kcal (0.96–5.02 MJ) in three experiments.

2. In the first experiment four subjects consumed one-ninth, one-third or one-half of the daily allowance and the oxygen consumption was measured for 3 h after the meal. The response was unrelated to the size of the meal.

3. Resting conditions were rigidly controlled in the second experiment. Each woman reclined on a bed for 5–7 h while the effect of a meal providing 600 or 900 kcal (2.51 or 3.77 MJ) for the two lighter subjects and 800 or 1200 kcal (3.35 or 5.02 MJ) for two heavier subjects was measured. A greater increment in energy expenditure was obtained after the larger meal for each subject. The effect of two 30 min walks before and after the large meal was negligible.

4. In a third experiment the effect of exercise was measured with five women consuming 900 kcal (3.77 MJ) (a) followed by 5 h rest and (b) preceded and followed by exercise (two 30 min walks on a treadmill). The energy increment during 90 min after the meal was equivalent in (a) to 15 kcal (63 kJ) per h and in (b) to 16 kcal (67 kJ) per h, whereas the response following exercise but without food was insignificant.