A randomized controlled trial of a moderate-fat, low-energy diet compared with a low fat, low-energy diet for weight loss in overweight adults.

Context: Long-term success in weight loss with dietary treatment has been elusive.

Objective: To evaluate a diet moderate in fat based on the Mediterranean diet compared to a standard low-fat diet for weight loss when both were controlled for energy.

Design: A randomized, prospective 18 month trial in a free-living population.

Patients: A total of 101 overweight men and women (26.5-46 kg/m(2)).

Intervention: (1) Moderate-fat diet (35% of energy); (2) low-fat diet (20% of energy).

Main Outcome Measurements: Change in body weight.

Results: After 18 months, 31/50 subjects in the moderate-fat group, and 30/51 in the low fat group were available for measurements. In the moderate-fat group, there were mean decreases in body weight of 4.1 kg, body mass index of 1.6 kg/m(2), and waist circumference of 6.9 cm, compared to increases in the low-fat group of 2.9 kg, 1.4 kg/m(2) and 2.6 cm, respectively; P < or = 0.001 between the groups. The difference in weight change between the groups was 7.0 kg. (95% CI 5.3, 8.7). Only 20% (10/51) of those in the low-fat group were actively participating in the weight loss program after 18 months compared to 54% (27/50) in the moderate-fat group, (P<0.002). The moderate-fat diet group was continued for an additional year. The mean weight loss after 30 months compared to baseline was 3.5 kg (n = 19, P = 0.03).

Conclusions: A moderate-fat, Mediterranean-style diet, controlled in energy, offers an alternative to a low-fat diet with superior long-term participation and adherence, with consequent improvements in weight loss.