Background: Metabolic rate is known to rise above basal levels after eating, especially following protein consumption. Yet, this postprandial rise in metabolism appears to vary among individuals. This study examined changes in energy expenditure in response to ingestion of a high protein, high fat (HPHF) meal versus an isocaloric high protein, low fat (HPLF) meal in underweight, normal weight, or overweight females (n = 21) aged 19-28 years.
Methods: Energy expenditure, measured using indirect calorimetry, was assessed before and every 30 minutes for 3.5 hours following consumption of the meals on two separate occasions. Height and weight were measured using standard techniques. Body composition was measured using bioelectrical impedance analysis.
Results: Significant positive correlations were found between body mass index (BMI) and baseline metabolic rate (MR) (r = 0.539; p = 0.017), between body weight and baseline MR (r = 0.567; p = 0.011), between BMI and average total change in MR (r = 0.591; p = 0.008), and between body weight and average total change in MR (r = 0.464; p = 0.045). Metabolic rate (kcal/min) was significantly higher in the overweight group than the normal weight group, which was significantly higher than the underweight group across all times and treatments. However, when metabolic rate was expressed per kg fat free mass (ffm), no significant difference was found in postprandial energy expenditure between the overweight and normal groups. Changes in MR (kcal/min and kcal/min/kg ffm) from the baseline rate did not significantly differ in the underweight (n = 3) or in the overweight subjects (n = 5) following consumption of either meal at any time. Changes in MR (kcal/min and kcal/min/kg ffm) from baseline were significantly higher in normal weight subjects (n = 11) across all times following consumption of the HPHF meal versus the HPLF meal.
Conclusion: There is no diet-induced thermogenic advantage between the HPHF and HPLF meals in overweight and underweight subjects. In contrast, in normal weight subjects, ingestion of a HPHF meal significantly increases MR (69.3 kcal/3.5 hr) versus consumption of a HPLF meal and provides a short-term metabolic advantage.