The volume of the stomach is increased in obese individuals when compared to their lean counterparts. This might suggest that increased food intake causes an increase in the size of the stomach over time. Further, it might be assumed that reducing food intake may have a reverse effect on the stomach, such that volume is reduced. This is important because it is known that satiety is dictated in part by stretch receptors on the stomach wall, and if these receptors are activated at a lower threshold because the stomach is smaller, food intake may be curtained more quickly. This is the basis for the uses of stomach reduction operations and appears to be an effective way of decreasing subsequent food intake. Some research suggests that stomach volume can be reduced with energy restriction, resulting in the enlarged stomach of obese individuals reducing in size equal to lean individuals.
For example, researchers1 have fed obese but healthy individuals (age 19 to 50 years with a body mass index of ≥27kg/m2) either a very low energy diet or an ad libitum diet for 4 weeks. The very low calorie diet consisted of a formula that contained 600kcal. At baseline the gastric capacity of the subjects was assessed by insertion of a latex balloon that was expanded within the stomach until discomfort was experienced, and this process was repeated after the 4 weeks diet protocol. The low calorie diet caused the subjects to lose 9.1kg of body weight, but the study did not differentiate between lean mass and body fat. This amount represented about ≥5% of body weight, suggesting good compliance with the very low calorie formula. In contrast the control group lost 0.02kg of weight, which was not significant from baseline.
The gastric capacity of the diet group was reduced by 27%, with no significant change in the control group from baseline. Based on the use of a second index of stomach volume, the volume in the diet group was shown to be reduced by 36%, with no change in the control group. The correlation between the weight lost and the reduced stomach capacity was positive but not significant. Comparisons of the post-diet stomach volume of the obese women with that measured in normal weight women by another study showed that there was no significant difference. These results suggest that stomach capacity can be reduced in obese individuals by calorie restriction. However, it is not clear if it was the formula diet or the calorie restriction that caused this effect as no control was performed. Evidence also suggests that post dieting, this volume reduction would be reversed.
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