Susan Carnell

BACKGROUND: Childhood obesity increases the risk of obesity in adulthood, but how parental obesity affects the chances of a child's becoming an obese adult is unknown. We investigated the risk of obesity in young adulthood associated with both obesity in childhood and obesity in one or both parents. METHODS: Height and weight measurements were abstracted from the records of 854 subjects born at a health maintenance organization in Washington State between 1965 and 1971. Their parents' medical records were also reviewed. Childhood obesity was defined as a body-mass index at or above the 85th percentile for age and sex, and obesity in adulthood as a mean body-mass index at or above 27.8 for men and 27.3 for women. RESULTS: In young adulthood (defined as 21 to 29 years of age), 135 subjects (16 percent) were obese. Among those who were obese during childhood, the chance of obesity in adulthood ranged from 8 percent for 1- or 2-year-olds without obese parents to 79 percent for 10-to-14-year-olds with at least one obese parent. After adjustment for parental obesity, the odds ratios for obesity in adulthood associated with childhood obesity ranged from 1.3 (95 percent confidence interval, 0.6 to 3.0) for obesity at 1 or 2 years of age to 17.5 (7.7 to 39.5) for obesity at 15 to 17 years of age. After adjustment for the child's obesity status, the odds ratios for obesity in adulthood associated with having one obese parent ranged from 2.2 (95 percent confidence interval, 1.1 to 4.3) at 15 to 17 years of age to 3.2 (1.8 to 5.7) at 1 or 2 years of age. CONCLUSIONS: Obese children under three years of age without obese parents are at low risk for obesity in adulthood, but among older children, obesity is an increasingly important predictor of adult obesity, regardless of whether the parents are obese. Parental obesity more than doubles the risk of adult obesity among both obese and nonobese children under 10 years of age.

CONTEXT: Polymorphisms within the FTO gene have consistently been associated with obesity across multiple populations. However, to date, it is not known whether the association between genetic variation in FTO and obesity is mediated through effects on energy intake or energy expenditure. OBJECTIVE: Our objective was to examine the association between alleles of FTO known to increase obesity risk and measures of habitual appetitive behavior. METHODS: The intronic FTO single nucleotide polymorphism (rs9939609) was genotyped in 3337 United Kingdom children in whom measures of habitual appetitive behavior had been assessed using two scales (Satiety Responsiveness and Enjoyment of Food) from the Child Eating Behaviour Questionnaire, a psychometric tool that has been validated against objective measures of food intake. Associations of FTO genotype with indices of adiposity and appetite were assessed by ANOVA. RESULTS: As expected, the A allele was associated with increased adiposity in this cohort and in an independent case-control replication study of United Kingdom children of similar age. AA homozygotes had significantly reduced Satiety Responsiveness scores (P = 0.008, ANOVA). Mediation analysis indicated that the association of the AA genotype with increased adiposity was explained in part through effects on Satiety Responsiveness. CONCLUSIONS: We have used a unique dataset to examine the relationship between a validated measure of children's habitual appetitive behavior and FTO obesity risk genotype and conclude that the commonest known risk allele for obesity is likely to exert at least some of its effects by influencing appetite.