[Required Effekt Sizes of Preventive Measures for Overweight in Children and Adolescents]. / Wie groß muss die Wirkung von Prävention auf das Übergewicht von Kindern und Jugendlichen sein?

BACKGROUND AND AIM OF THE STUDY: Successful preventive measures can stop a further increase in the prevalence of overweight in children and adolescents. However, up to now, the required effect sizes of interventions for reducing childhood overweight remain unclear. The calculation of the energy gap (excess calories consumed over calories expended) offers the possibility to estimate the required effect sizes. In this work 2 approaches to calculate the energy gap will be compared. METHODS: Longitudinal data of 1690 children and adolescents of the Kiel Obesity Prevention Study (KOPS) on measured height, weight, fat mass and fat-free mass (using bioelectrical impedance analysis) at age 6 and 10 years will be used to calculate energy gap with 2 different approaches: (i) using age-independent changes in fat mass and fat-free mass (old approach) and (ii) using a mathematic model of weight dynamic (new approach). RESULTS: Energy gap according to the old approach was 140 kcal/day; by contrast, new modeling resulted in an energy gap between 270 and 370 kcal/day. Both, BMI and fat mass were suitable to calculate energy gap and led to nearly same results. Exceeding the 90(th) percentile of BMI or fat mass (incidence approach) as well as large changes within the normal range (i.e. between the 10(th) and the 90(th) percentile) led to large energy gaps. Thus, all children with large energy gaps have to be characterized as at risk for overweight. CONCLUSION: The new approach seems to be convincing because it considered the additional energy expenditure for building fat-free mass due to increasing age and weight.Calculating energy gap offers a new approach for prevention of overweight. It shows that the required effect sizes of prevention measures have to be in a region of 140 to 400 kcal/day. This differs clearly from energy reduction of diets in the therapy of obesity.

Adiposity rebound is misclassified by BMI rebound.

BACKGROUND/OBJECTIVES: Adiposity rebound (AR) is defined as the nadir or the inflexion point of body mass index (BMI) percentiles between the age of 3 and 7 years. An early rebound is seen as a risk of obesity and, thus, AR is considered as a suitable time period for prevention. As BMI does not reflect body composition, we aimed to examine the rebounds of fat mass index (FMI) and fat-free mass index (FFMI) together with BMI. SUBJECTS/METHODS: Cross-sectional data of 19 264 children aged 3-11 years were pooled from three German studies (Kiel Obesity Prevention Study, the project 'Better diet. More exercise. KINDERLEICHT-REGIONS' and regular examinations of Jena children). Height and weight were measured. Fat mass (FM) and fat-free mass (FFM) were obtained from bioelectrical impedance analysis and analysed using a population-specific algorithm. Percentiles of BMI, FMI and FFMI were constructed by the LMS method. RESULTS: Both BMI and FMI percentiles showed a rebound, whereas FFMI percentiles steadily increased with age. On P90, FMI rebound was about 1.6-1.8 years later compared with that of BMI, that is, at ages 4.2 years (BMI) and 5.8 years (FMI) in boys and at 4.2 years (BMI) and 6.0 years (FMI) in girls. At AR, the slope of the BMI-P90 was explained by increases in FFMI rather than FMI. By contrast, at FMI rebound, the slope of BMI was strongly related to FMI. CONCLUSIONS: BMI rebound does not equal the rebound of FM. At AR, the slope in BMI is determined by the increase in FFMI. AR should be defined as FMI rebound rather than BMI rebound.

[Longitudinal data of the Kiel Obesity Prevention Study (KOPS)]. / Längsschnittdaten der Kieler Adipositas-Präventionsstudie (KOPS).

The Kiel Obesity Prevention Study (KOPS) has been performed since 1996. Examinations were performed at age 6, 10 and 14 years. In addition, birth weight as well as height and weight at age 2 years were collected retrospectively. For the study 4,997, 1,671 and 748 children were recruited at baseline (at age 6 years) as well as at 4 and 8-year follow-up, respectively. In this paper we will analyze and discuss (i) the important time period for preventive measures, (ii) effect sizes needed for successful interventions and (iii) suitable approaches for preventive measures. The main results were: (i) at age 6 years persistence of overweight was 69% while at younger ages persistence was 21% only. Thus, school entry was shown to be an important period for preventive measures. (ii) Interventions have to reduce energy balance by 140 kcal/day to prevent overweight (e.g. a reduction of energy intake). (iii) Prevention programs should involve the family and focus on increasing physical activity.

Effects of brief perturbations in energy balance on indices of glucose homeostasis in healthy lean men.

BACKGROUND: Little is known about the effects of short-term caloric restriction (CR) and overfeeding (OF) on glucose homeostasis in healthy lean individuals. In addition, it remains unclear whether the effects of CR and OF are reversed by a complementary feeding period. METHODS: Ten healthy men participated in two cycles of controlled 7-day periods of CR and refeeding (RF; protocol A), and OF and CR (protocol B) at ±60% energy requirement. At baseline, insulin sensitivity (IS) was assessed by euglycemic clamp (M). Before and during each feeding cycle, fasting and oral glucose tolerance test-derived indices were used to estimate glucose tolerance, IS and glucose-stimulated insulin secretion. RESULTS: Clamp tests revealed normal IS at baseline (M-values 9.4±2.1 mg kg⁻¹ min⁻¹, coefficient of variation (CV)(inter) 22%). M-values were significantly correlated with indices of IS. In protocol A, CR-induced weight loss (-3.0±0.4 kg) was associated with an increase in fasting IS. Postprandial IS and glucose-stimulated insulin secretion remained unchanged, but glucose tolerance decreased. RF decreased fasting and postprandial IS at increased glucose-stimulated insulin secretion. In protocol B, OF significantly increased the body weight (+1.6±0.9 kg). Concomitantly, fasting and postprandial IS decreased at increased glucose-stimulated insulin secretion. Subsequent CR reversed these effects. Inter-individual variability in indices of glucose metabolism was high with coefficients of variation ranging from 9 to 59%. CONCLUSION: Significant changes in glucose metabolism are evident within 7-day periods of controlled OF and underfeeding. Although IS was impaired at the end of the CR-RF cycle, IS was normalized after the OF-CR cycle. At different feeding regimens, homeostatic responses of glucose metabolism were highly variable.