Objective: To evaluate the effects of 2 low-calorie diets but with different distributions of calories throughout the day on weight loss and other major obesity-related metabolic parameters.
Methods: We randomly assigned 42 nonsmoking homemakers (age = 46.3 ± 2.3 years, body mass index [BMI] = 35.7 ± 0.8 kg/m(2), mean ± SD) in 2 groups of 21 subjects (G1 and G2). The participants underwent a 3 month individualized Mediterranean-style diet (55% carbohydrate, 30% fat, 15% protein and fiber > 30 g), calorie (600 kcal daily deficit compared to the total energy expenditure measured by a metabolic Holter). Diets consisted of the same food and complied with cardiovascular disease prevention guidelines but differed in the distribution of calories throughout the day (G1: 70% breakfast, morning snack, lunch and 30% afternoon snack and dinner; G2: 55 breakfast, morning snack, lunch and 45% afternoon snack and dinner). Dual-energy X-ray absorptiometry was used for pre- and postintervention body composition assessment.
Results: Thirty-six subjects completed the study (G1 = 18, G2 = 18). Both groups had significant improvements in body composition and metabolic parameters but G1 had enhanced results for weight loss (G1: -8.2 ± 3.0 kg; G2: -6.5 ± 3.4 kg; p = 0.028), waist circumference reduction (G1: -7 ± 0.6 cm; G2: -5 ± 0.3 cm; p = 0.033), and fat mass loss (G1: -6.8 ± 2.1 kg, G2: -4.5 ± 2.9 kg, p = 0.031; mean ± SD). Improvements were detected in both groups for blood pressure and blood and lipid parameters. G1 subjects showed a greater improvement in insulin sensitivity measured by homeostasis model assessment-estimated insulin resistance (G1: -1.37 ± 0.27, G2: -0.74 ± 0.12, p = 0.017).
Conclusions: These data suggest that a low-calorie Mediterranean diet with a higher amount of calories in the first part of the day could establish a greater reduction in fat mass and improved insulin sensitivity than a typical daily diet.
Keywords: 7-day diet diaries; Mediterranean; body composition; breakfast; diet; fat loss; lifestyle; metabolic Holter; morning.