Reduced risk for overweight and obesity in 5- and 6-y-old children by duration of sleep--a cross-sectional study.

OBJECTIVE: To assess the relationship between sleep duration and adiposity in 5- and 6-y-old Bavarian children. DESIGN: Cross-sectional study. SUBJECTS: A total of 6862 German children aged 5-6 y participating in the obligatory health examination in Bavaria, southern Germany. MEASUREMENTS: Routine data were collected on the height and weight of children at the time of school entry in six public health offices in 1999 and in another two in 2000. Body fat mass was estimated by BIA performed in three of those offices. An extensive questionnaire was given to all children's parents in order to assess risk factors for overweight and obesity. The main outcome measures were overweight, defined by a body mass index (BMI) above the 90th centile and obesity, defined by a BMI above the 97th centile for the German children in Bavaria. Excessive body fat was defined as fat mass above the 90th centile for all German children seen in this survey. The main exposure was usual sleeping hours on week days. RESULTS: The prevalence of obesity decreased by duration of sleep: < or =10 h, 5.4% (95% CI 4.1-7.0), 10.5-11.0 h, 2.8% (95% CI 2.3-3.3), and > or =11.5 h, 2.1% (95% CI 1.5-2.9). Similar relations were found with the prevalence of overweight and excessive body fat. These effects could not be explained by confounding due to a wide range of constitutional, sociodemographic and lifestyle factors. The adjusted odds ratio for obesity were: for sleeping 10.5-11.0 h, 0.52 (95% CI 0.34-0.78) and 0.46 (95% CI 0.28-0.75) for sleeping 11.5 h. CONCLUSION: The effect of sleep duration on obesity in children reflects a higher body fat composition and appears to be independent of other risk factors for childhood obesity.

Excessive infant crying: often not confined to the first 3 months of age.

Excessive crying/fussing in infancy may account for serious problems in mother-infant interactions but is believed to be self-limiting around the age of 3 months. A random digit dialling telephone survey weighted by sex, age, and population density and yielding 662 children aged 9 to <36 months was used to estimate prevalence and the proportion of cases where this problem extends beyond the third month postpartum. Excessive infant crying/fussing during the first 3 months of age was found in 21.0% (95% CI 17.9-24.1) and persisted for longer in 39.6% (95% CI 31.5-47.7) of these. Professionals consulting parents on crying problems should take into account its possible persistence for longer periods of time.

Restrained eating and leptin levels in overweight preadolescent girls.

The relationship between restrained eating and leptin levels 6 months later was investigated. Twenty obese girls, ages 8-12 years, were studied. Degree of restrained eating was assessed with the Three-Factor Eating Questionnaire. Serum leptin levels were determined 6 months after the measurement of cognitive restraint. Restraint score and leptin levels showed a significant negative correlation (r = -0.43) The correlation was also significant when controlling for fat mass (r = -0.61), which is the strongest biological predictor of leptin levels. If lower leptin levels cause a diminished energy expenditure, then paradoxically, restrained eating might be responsible for weight gain in obese individuals because of its promotion of a positive energy balance.

Resting metabolic rate in preadolescent girls at high risk of obesity.

OBJECTIVE: To investigate whether children at high risk of obesity have a reduced resting metabolic rate (RMR). DESIGN: Cross-sectional study. SUBJECTS: 93 healthy girls (age: 8-12 y) were allocated to one of four groups, according to the subjects' and their parents' weight status: group 1, overweight children with both parents overweight (OB/OB2; n = 17); group 2, normal weight children with both parents overweight (N/OB2; n = 28); group 3, overweight children of discordant parents (OB/OB1; n = 21) and group 4, normal weight children with both parents normal weight (N/OB0; n = 27). MEASUREMENTS: Weight, height, fat-free mass (FFM) and fat mass (FM) by bioelectrical impedance analysis (BIA), RMR (indirect calorimetry) for the duration of 25 min. RESULTS: Controlling for disparities in body composition, age and physical maturity, significant differences were found in adjusted group means of RMR (OB/OB2 1181 kcal/d; N/OB2 1276 kcal/d; OB/OB1 1234 kcal/d; N/OB0 1199 kcal/d; P < 0.02) with the OB/OB2 girls showing the lowest energy expenditure. CONCLUSION: We found evidence that preadolescent girls at risk of obesity, are not generally predisposed to a higher body weight, because of a greater metabolic efficiency. In fact, our data show that more emphasis should be laid on defining different subgroups of both overweight and normal weight subjects in studies investigating metabolic rate.

A comparison of resting metabolic rate, self-rated food intake, growth hormone, and insulin levels in obese and nonobese preadolescents.

The objective was to investigate metabolic (resting metabolic rate), behavioral (energy intake), and endocrine variables (fasting insulin and growth hormone levels) potentially responsible for a positive energy balance in obese children in a cross-sectional study. The study was in 25 obese children aged 8 to 12 years and 21 nonobese children of the same age range. Weight, height, lean body mass (LBM) and fatmass (FM) were measured by bioelectrical impedance analysis, resting metabolic rate (indirect calorimetry) for the duration of 25 min, 7-day food records and fasting levels of insulin and human growth hormone (HGH). In the total sample, no differences were found in resting metabolic rate (RMR controlled for differences in weight) and energy intake between groups, whereas fasting insulin level was significantly higher and basal growth hormone concentration was significantly lower in the obese children. In RMR, there were significant age-dependent differences only in 10-year-old children, with the obese subjects showing lower values. The results fit in a multidimensional model, taking into account a critical period in prepubertal age for the development of childhood obesity. This period may be characterized by a reduced RMR, which results in an increased body weight, even if there is no excessive energy intake.

Beta 3-adrenergic-receptor allele distributions in children, adolescents and young adults with obesity, underweight or anorexia nervosa.

OBJECTIVE: The missense mutation (64Trp to 64Arg) in the beta 3-adrenergic-receptor has previously been described to confer a genetic predisposition to the development of obesity. DESIGN: To test the hypothesis we evaluated allele frequencies in children, adolescents and young adults who belonged to different weight groups that were delineated with percentiles for the body mass index (BMI; kg/m2). SUBJECTS: 99 underweight probands (BMI < or = 15th percentile). 80 normal weight probands (BMI: 5th-85th percentile). 238 obese children and adolescents (BMI > or = 97th percentile). 84 patients with anorexia nervosa (AN). MEASUREMENTS: The cohorts were screened by polymerase chain reaction with subsequent restriction fragment length polymorphism (PCR-RFLP) analysis. Data were statistically analysed for association. In addition to these case control studies, the transmission disequilibrium test (TDT) was applied to 80 families of obese probands and to 52 families of patients with AN. RESULTS: Both the tests for association and linkage were negative. The Trp64Arg allele frequencies in the three weight groups (obesity: 0.071; normal weight: 0.081; underweight: 0.056) and the AN patients (0.054) were similar. Extremely obese individuals showed no excess of the Trp64Arg allele. No homozygotes for the Trp64Arg allele were detected. CONCLUSION: Heterozygosity for the Trp64Arg allele is not of major importance in regulation of body weight in individuals younger than 35 y. Additionally, the extreme obese subgroup is not enriched for the polymorphism.

Evaluation of a Cys23Ser mutation within the human 5-HT2C receptor gene: no evidence for an association of the mutant allele with obesity or underweight in children, adolescents and young adults.

Serotonin is a neurotransmitter involved in a large number of psychophysiological processes including the regulation of mood, arousal, aggression, sleep, learning, nociceptions, nerve growth and importantly, appetitive functions. Alterations of 5-HT receptor activity have been shown to occur in many psychiatric diseases including depression, anxiety, eating disorders, schizophrenia etc. Hence, genetic variation in genes coding for serotonin receptor proteins might well be involved in the genetic predisposition to these diseases and therefore are of great pharmacogenetic relevance. Knockout mice deficient of a functional 5-HT2C receptor have implicated a potential role of this receptor subtype in the serotonergic control of appetite. A Cys23Ser mutation in the human 5-HT2C receptor gene discovered recently prompted us to investigate this mutation with regard to the development of human obesity. We have evaluated this mutation in 241 obese children and adolescents (mean BMI > or = 97th percentile), 80 normal weight children (BMI 5th-85th percentile) and 92 underweight probands (BMI < or = 15th percentile) for a possible association with obesity. The frequencies of the mutant allele in all three weight groups (obese subjects: 0.1597; normal weight: 0.168; underweight: 0.1575) were very similar. Association as well as linkage studies were negative. Therefore it is unlikely that this receptor mutation plays a direct role in the development of human obesity.

Resting metabolic rate and diet-induced thermogenesis in restrained and unrestrained eaters.

OBJECTIVE: The hypothesis was studied whether restrained eaters had reduced resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) and whether the effect was caused by weight cycling. METHOD: 12 restrained and 12 unrestrained eaters (classified by the Three Factor Eating Questionnaire) were studied with regard to RMR an DIT by direct calorimetry using a ventilated hood system. In a second study 12 weight cycling restrained eaters and 12 weight stable restrained eaters were compared. RESULTS: Restrained eaters had significantly lower RMR than unrestrained eaters. No difference in DIT was found. Weight cycling and no weight cycling restrained eaters did not differ with regard to RMR and DIT. DISCUSSION: These data indicate that restrained eating but not weight cycling significantly reduces RMR.