A PUFA-rich diet improves fat oxidation following saturated fat-rich meal

Purpose To determine substrate oxidation responses to saturated fatty acid (SFA)-rich meals before and after a 7-day polyunsaturated fatty acid (PUFA)-rich diet versus control diet. Methods Twenty-six, normal-weight, adults were randomly assigned to either PUFA or control diet. Following a 3-day lead-in diet, participants completed the pre-diet visit where anthropometrics and resting metabolic rate (RMR) were measured, and two SFA-rich HF meals (breakfast and lunch) were consumed. Indirect calorimetry was used to determine fat oxidation (Fox) and energy expenditure (EE) for 4 h after each meal. Participants then consumed a PUFA-rich diet (50 % carbohydrate, 15 % protein, 35 % fat, of which 21 % of total energy was PUFA) or control diet (50 % carbohydrate, 15 % protein, 35 % fat, of which 7 % of total energy was PUFA) for the next 7 days. Following the 7-day diet, participants completed the post-diet visit. Results From pre- to post-PUFA-rich diet, there was no change in RMR (16.3 +/- 0.8 vs. 16.4 +/- 0.8 kcal/20 min) or in incremental area under the curve for EE (118.9 +/- 20.6-126.9 +/- 14.1 kcal/8h, ns). Fasting respiratory exchange ratio increased from pre- to post-PUFA-rich diet only (0.83 +/- 0.1-0.86 +/- 0.1, p < 0.05). The postprandial change in Fox increased from pre-to post-visit in PUFA-rich diet (0.03 +/- 0.1-0.23 +/- 0.1 g/15 min for cumulative Fox; p < 0.05), whereas controls showed no change. Conclusions Adopting a PUFA-rich diet initiates greater fat oxidation after eating occasional high SFA meals compared to a control diet, an effect achieved in 7 days.