Long-term effects of consumption of full-fat or reduced-fat products in healthy non-obese volunteers: assessment of energy expenditure and substrate oxidation.

A study was performed to evaluate long-term (6-month) effects of consumption of full-fat products or reduced-fat products on energy and substrate metabolism. Subjects (age, 19 to 35 years; body mass index [BMI], 21 to 28 kg. m-2) were studied during a 36-hour stay in a respiration chamber, before (16 men) and in the third month (16 men) and sixth month (19 men and 17 women) of the study. The diet intervention caused, on average, a change in fat intake of (mean +/- SE) +23 +/- 31 g/d (P < .001) in the full-fat group and of -5 +/- 29 g/d (P .05) in the reduced-fat group. Twenty-four-hour energy expenditure (EE), sleeping metabolic rate (SMR), diet-induced thermogenesis (DIT), and EE for physical activity (ACT) were not different between the groups. Fat oxidation was significantly (P < .05) increased in the full-fat group and was not different from fat intake. During the 6 months of the study, body mass and fat mass were significantly increased in subjects of the full-fat group, whereas there were no changes in body mass or body composition in subjects of the reduced-fat group. It is concluded that in the long run, avoidance of a diet with full-fat products will promote body weight and fast stability.