Background Trials comparing the effectiveness and safety of weight-loss diets are frequently limited by short follow-up times and high dropout rates. Methods In this 2-year trial, we randomly assigned 322 moderately obese subjects (mean age, 52 years; mean body-mass index [the weight in kilograms divided by the square of the height in meters], 31; male sex, 86%) to one of three diets: low-fat, restricted-calorie; Mediterranean, restricted-calorie; or low-carbohydrate, non-restricted-calorie. Results The rate of adherence to a study diet was 95.4% at 1 year and 84.6% at 2 years. The Mediterranean-diet group consumed the largest amounts of dietary fiber and had the highest ratio of monounsaturated to saturated fat (P<0.05 for all comparisons among treatment groups). The low-carbohydrate group consumed the smallest amount of carbohydrates and the largest amounts of fat, protein, and cholesterol and had the highest percentage of participants with detectable urinary ketones (P<0.05 for all comparisons among treatment groups). The mean weight loss was 2.9 kg for the low-fat group, 4.4 kg for the Mediterranean-diet group, and 4.7 kg for the low-carbohydrate group (P<0.001 for the interaction between diet group and time); among the 272 participants who completed the intervention, the mean weight losses were 3.3 kg, 4.6 kg, and 5.5 kg, respectively. The relative reduction in the ratio of total cholesterol to high-density lipoprotein cholesterol was 20% in the low-carbohydrate group and 12% in the low-fat group (P = 0.01). Among the 36 subjects with diabetes, changes in fasting plasma glucose and insulin levels were more favorable among those assigned to the Mediterranean diet than among those assigned to the low-fat diet (P<0.001 for the interaction among diabetes and Mediterranean diet and time with respect to fasting glucose levels). Conclusions Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets. The more favorable effects on lipids (with the low-carbohydrate diet) and on glycemic control (with the Mediterranean diet) suggest that personal preferences and metabolic considerations might inform individualized tailoring of dietary interventions. (ClinicalTrials.gov number, NCT00160108.

There is a consensus that interventions to prevent and treat childhood obesity should involve the family; however, the extent of the child's involvement has received little attention. The goal of the present study was to evaluate the relative efficacy of treating childhood obesity via a familybased health-centred intervention, targeting parents alone v. parents and obese children together. Thirty-two families with obese children of 6-11 years of age were randomised into groups, in which participants were provided for 6 months a comprehensive educational and behavioural programme for a healthy lifestyle. These groups differed in their main agent of change: parents-only v. the parents and the obese child. In both groups, parents were encouraged to foster authoritative parenting styles (parents are both firm and supportive; assume a leadership role in the environmental change with appropriate granting of child's autonomy). Only the intervention aimed at parents-only resulted in a significant reduction in the percentage overweight at the end of the programme (P¼ 0·02) as well as at the 1-year follow-up meeting. The differences between groups at both times were significant (P,0·05). A greater reduction in food stimuli in the home (P,0·05) was noted in the parents-only group. In both groups, the parents' weight status did not change. Regression analysis shows that the level of attendance in sessions explained 28 % of the variability in the children's weight status change, the treatment group explained another 10 %, and the improvement in the obesogenic load explained 11 % of the variability. These results suggest that omitting the obese child from active participation in the health-centred programme may be beneficial for weight loss and for the promotion of a healthy lifestyle among obese children.

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