An ad libitum reduced-GL diet appears to be a promising alternative to a conventional diet in obese adolescents. Large-scale randomized controlled trials are needed to further evaluate the effectiveness of reduced-GL and -glycemic index diets in the treatment of obesity and prevention of type 2 diabetes.

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Context Fast food consumption has increased greatly among children in recent years, in tandem with the obesity epidemic. Fast food tends to promote a positive energy balance and, for this reason, may result in weight gain. However, if fast food and obesity are causally related, the question arises of why some children who frequently eat fast food do not become overweight. Objective To test the hypothesis that overweight adolescents are more susceptible to the adverse effects of fast food than lean adolescents. Design and Setting In study 1, we fed participants an "extra large" fast food meal in a naturalistic setting (a food court). The participants were instructed to eat as much or little as desired during this 1-hour meal. In study 2, we assessed energy intake under free-living conditions for 2 days when fast food was consumed and 2 days when it was not consumed. Data were collected in Boston, Mass, between July 2002 and March 2003. Participants Overweight (n=26) and lean (n=28) adolescents aged 13 to 17 years. Overweight was defined as a body mass index exceeding sex-and age-specific 85th percentiles based on the 2000 Centers for Disease Control and Prevention growth charts. Main Outcome Measures Energy intake determined by direct observation in study 1 and by unannounced 24-hour dietary recalls, administered by telephone, in study 2. Results In study 1, mean (SEM) energy intake from the fast food meal among all participants was extremely large (1652 [87] kcal), accounting for 61.6% (2.2%) of estimated daily energy requirements. Overweight participants ate more than lean participants whether energy was expressed in absolute terms (1860 [129] vs 1458 [107] kcal, P=.02) or relative to estimated daily energy requirements (66.5% [3.1%] vs 57.0% [2.9%], P=.03). In study 2, overweight participants consumed significantly more total energy on fast food days than non-fast food days (2703 [226] vs 2295 [162] kcal/d; +409 [142] kcal/d; P=.02), an effect that was not observed among lean participants (2575 [157] vs 2622 [191] kcal/d;-47 [173] kcal/d; P=.76). Conclusions In this study, adolescents overconsumed fast food regardless of body weight, although this phenomenon was especially pronounced in overweight participants. Moreover, overweight adolescents were less likely to compensate for the energy in fast food, by adjusting energy intake throughout the day, than their lean counterparts.

We showed no evidence that an LGD and an LFD differ in efficacy for the reduction of BMI or aspects of metabolic syndrome in obese Hispanic youth. Both diets decreased the BMI z score when prescribed in the context of a culturally adapted, comprehensive weight-reduction program.