ESPE Abstracts

Background: Adults have a weight that is normal for them. This is referred to as their ‘set-point’ for weight. Studies have shown physiological protection of this set-point, explaining why most obese adults who diet eventually regain weight.

Objective and hypotheses: We hypothesised that set-points for weight, and their physiological defence, are flexible in childhood but become fixed sometime around puberty. We aimed to show that obese children who lost weight had less ‘reflex’ changes in satiety hormone profiles that would drive weight regain, compared with adolescents who had lost weight.

Method: Prospective cohort study. 41 subjects; 21 obese pre-pubertal children (age 3–7 years; 11 males) and 20 obese adolescents (age 14–18 years; ten males). Obesity defined as BMI >2.4 SDS. Subjects recruited as either ‘reducers’ (relative or absolute weight loss of ≧10% in the preceding 9–15 months) or maintainers (controls). Resting energy expenditure (REE), impedance and fasting and post-prandial satiety hormone profiles with subjective assessments of appetite were taken every 30 minutes over 3 h. Multilevel methods were used to model post-prandial hormone and satiety profiles.

Results: Post-pubertal adolescents had 31% lower Ghrelin concentrations (4–51%, P=0.03) and 50% higher Amylin concentrations than pre-pubertal children (18–91%, P=0.001). Children reducing weight reached maximum GIP slower than weight maintainers (P=0.05). The association between Ghrelin, Amylin and GIP concentration and weight change was similar for both pre- and post-pubertal children (P=0.79, P=0.39, P=0.79 respectively). No associations were found for Peptide YY, PP, active GLP1. Regarding satiety, post-pubertal adolescents who lost weight reported less hunger (P<0.001) and higher satiety (P=0.03) than pre-pubertal children. REE in pre-pubertal weight reducers and maintainers were similar (50 kcal lower, −143 to 242, P=0.6) but post-pubertal reducers had 250 kcal lower REE compared to post-pubertal maintainers (−68 to 572, P=0.1).

Conclusion: Satiety hormone profiles were similar between pre- and post-pubertal subjects, and appeared to contrast with previously published adult data, where weight reduction leads to sustained increases in Ghrelin and reductions in the other hormones. These findings indicate that the physiological mechanisms which act to protect against weight change, may develop later than in the adolescent years.

Funding: Murdoch Children’s Research Institute, Melbourne, Australia.