Diet induced thermogenesis measured over 24h in a respiration chamber: effect of diet composition

OBJECTIVE: To study the effect of diet composition on diet-induced thermoge nesis (DIT) over 24h in a respiration chamber. SUBJECTS: Eight healthy female volunteers (age 27 +/- 3 y; body mass index, BMI 23 +/- 3 kg/m(2)). DIETS: A high protein and carbohydrate (HP/C) (60:10:30; percentage energy (E%)carbohydrate, fat and protein, respectively) and high fat (HF) (30:60:1 0 respectively) diet, both isoenergetic, isovolumetric, composed of normal food items and matched for organoleptic properties (taste, smelt, appearanc e). DESIGN: Subjects spent two 36 h periods each in a respiration chamber consu ming both test diets in random order. Components of 24h energy expenditure (24h EE): sleeping metabolic rate, DIT and activity induced energy expendit ure were measured. RESULTS: DIT was higher in all subjects while on the HP/C diet (1295 kJ/d v s 931 kJ/d; 14.6% vs 10.5% of energy intake; P < 0.02). There was no signif icant difference in other components or total 24 h EE, although there was a trend towards higher EE on the HP/C diet. CONCLUSION: A high protein and carbohydrate diet induces a greater thermic response in healthy individuals when compared to a high fat diet.