Acute effect of dietary fatty acid composition on postprandial thermogenesis and substrate oxidation in normal weight and obese females
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Background: The Composition of fatty acids in a diet may differentially affect metabolism, thus playing a role in the development of obesity. Our purpose was to study the effects of three high-fat (HF) meals with different dietary fatty acid compositions on diet induced thermogenesis (DIT) and substrate oxidation in obese premenopausal women. Methods: 15 healthy normal weight and 16 obese women, aged 18-39 years, participated in a single-blinded randomized cross over study, in which they consumed isocaloric HF meals (70% of energy from fat) rich in either saturated fat (SFA) (40% of total energy) , monounsaturated fat (MUFA) (42% of total energy) or polyunsaturated fat (PUFA) (42% of total energy). Indirect calorimetry was used to measure respiratory gases for a 5-hour postprandial period. Data collected was used to determine respiratory exchange ratio (RER) for assessing substrate oxidation, and energy expenditure for the determination of DIT. Results: For normal weight women, the area under the curve for DIT following the PUFA-rich HF meal was greater than that of the SFA- or MUFA-rich HF meals (19.9±1.4, 17.1±1.7 and 17.9±2.3 kcals/5-hours (p=0.02) for PUFA, MUFA and SFA, respectively). No significant difference was found in RER (0.86±0.01, 0.85±0.01 and 0.85±0.01 for PUFA, MUFA, and SFA-rich HF meals, respectively) or substrate utilization following the three different HF meals (24.4±1.9, 22.4±1.1 and 23.3±1.9 grams for cumulative postprandial carbohydrate oxidation following the PUFA, MUFA, and SFA-rich HF meals, respectively; 7.7±0.7, 8.3±0.5 and 8.2±0.6 grams for cumulative fat oxidation the PUFA, MUFA, and SFA-rich HF meals, respectively). For obese subjects there was a significant time effect on both substrate oxidation and DIT (p<0.05). No treatment difference was found in DIT (21.6±1.6, 22.0±1.9 and 21.3±1.8 kcals/5 hours for SFA, MUFA, and PUFA-rich HF meals, respectively) or substrate utilization following the three different HF meals (26.4±1.8, 26.5±1.0 and 27.7±1.2 grams for cumulative postprandial carbohydrate oxidation following the SFA, MUFA, and PUFA-rich HF meals, respectively; 9.9±0.8, 9.7±0.6 and 9.2±0.7 grams for cumulative fat oxidation the following SFA, MUFA, and PUFA-rich HF meals, respectively). Conclusions: Acute ingestion of a PUFA-rich HF meal induced a greater DIT in normal weight women compared to SFA- or MUFA-rich HF meals. No significant differences were found for substrate utilization. In obese women, acute ingestion of HF meals enriched in SFA, MUFA or PUFA did not elicit differences in substrate oxidation or DIT.