Diet-induced thermogenesis: variations among three isocaloric meal-replacement shakes.

Objective: We determined whether significant differences exist in diet-induced thermogenesis among three low-calorie (1042 kJ, or 250 kcal), liquid meal-replacement shakes of different macronutrient compositions: 1) 100% protein; 2) 62% protein, 28% carbohydrate, and 10% fat (high protein/low carbohydrate); and 3) 17% protein, 75% carbohydrate, and 8% fat (low protein/high carbohydrate).

Methods: Eight subjects (three men and five women) completed a randomized, double-blind, crossover investigation involving three separate resting-and-reclining energy expenditure measurements taken before and after consumption of one of the shakes. Resting-and-reclining metabolic gas-exchange measurements were taken for 30 min; subjects then drank a 20-oz shake, after which 3 h of additional resting-and-reclining gas-exchange measurements were taken.

Results: A statistically significant difference in diet-induced thermogenesis (P<0.02) was found between the low protein/high carbohydrate shake (79+- 48 kJ) and the high protein/low carbohydrate shake (209+/-108 kJ). No significant differences in diet-induced thermogenesis were found in comparison with the 100% protein shake (136+/-81 kJ). No significant differences in the respiratory exchange ratio over 3 h (P=0.33) were found.

Conclusions: Different types of low-calorie meal-replacement shakes do invoke significantly different thermogenic responses over a 3-h period. However, the 130-kJ (31-kcal) difference found in diet-induced thermogenesis represents only a small contribution to daily energy expenditure so that practical applications for weight-control management appear to be minimal.