Objective: To compare the influence of weight-reducing diets containing different amounts of protein and CHO on body composition in obese adolescents and to examine dietary and physical activity behaviours during follow-up.
Design: Prospective randomised study comparing two weight-reducing diets with the same energy (1750 kcal) and fat (31%) content, but different protein and carbohydrate contents: PROT- (15% protein, 54% CHO) vs PROT+ (19% protein, 50% CHO).
Patients: Massively obese 11- to 16-year-old children (32 boys and 89 girls).
Setting: A 9-month treatment in a medical centre (boarding school) plus a 2-y follow-up in free-living patients examined at home 1 and 2 y after treatment.
Measurements: Anthropometry, bioelectrical impedance, nutritional intakes and physical activity.
Results: Of the 121 eligible children (61 in PROT- and 60 in PROT+), 82% completed the trial until the end of weight loss treatment and 60% were followed 2 y after treatment. Body mass index (BMI) value at inclusion was 36.3 kg/m(2) or 4.3 z-scores (2.9-5.9). BMI z-score decreased to 1.7 at the end of treatment and went back to 2.8 (0.8-6.1) 2 y after treatment. This corresponded to a weight loss of 30.3 kg and weight regain of 21.3 kg. After treatment, energy intake increased and physical activity decreased. The contribution of energy ingested at breakfast decreased while snacking increased. For all measurements, no dietary group differences existed at baseline or at any time during the intervention and follow-up.
Conclusion: A higher protein content of the diet did not confer any benefit in the treatment of childhood obesity. Substantial weight loss was obtained with a moderately energy-restricted diet and normal fat content. After weight loss, mean weight increased in spite of moderate energy intake, together with a drift towards obesity-associated behavioural patterns. The causes of the inability to adopt normal weight subjects' behaviour permanently deserve to be investigated further.