In 1950 Otto Wolff set up one of the first clinics in the United Kingdom specifically for the study and treatment of obesity in children. His original observations on the effects of over-nutrition on the development of children and of the outcome of hospital treatment (Wolff, 1955; Lloyd et al., 1961) have never been surpassed. His continuing interest in the subject has promoted work into many aspects cellular, biochemical, psychological and epidemiological and, together with the studies of numerous workers in many countries, has greatly enhanced our knowledge of this important nutritional disorder. Nevertheless many questions wait for answers and many problems for solutions. This review will discuss some of them. Because obesity in children is only rarely associated with endocrine diseases or other syndromes, these will not be considered here and the topic remains that of 'simple obesity' in itself a grave misnomer!
The prevalence of overweight at ages 7 and 11 years and in late adolescence was compared in two nationally representative cohorts of British children born in 1946 and 1958. Overweight was defined as weight that exceeded the standard weight for height, age, and sex by more than 20% (relative weight greater than 120%). The prevalence of overweight among 7 year olds born in 1958 was nearly twice that among those born in 1946. Changes in infant feeding practices, food supply, and level of physical activity might be responsible for this difference. By adolescence the prevalence of obesity in both cohorts had increased but the difference between cohorts had almost disappeared. Around 9% of adolescent girls and 7% of adolescent boys were overweight. If infant feeding practices have an influence on prevalence of overweight at 7 years the data from the two cohorts suggest that such an effect does not persist. In neither cohort was there a significant relation between the prevalence of obesity and social class in boys, but in girls the prevalence was higher among those from the lower socioeconomic groups. Correlation coefficients showing the strength of the relation between relative weights at different ages were remarkably similar for both cohorts. The risk of being obese later in childhood for those who had not been obese at the age of 7 was less than one in 10, whereas for those with a relative weight greater than 130% the risk exceeded six in 10.
In a nationally representative cohort of 5362 children born in one week in March 1946 weights and heights were recorded at 6, 7, 11, 14, 20, and 26 years. Overweight was defined as a weight that exceeded the standard weight for height, age, and sex by more than 20% (relative weight greater than 120%). The prevalence of overweight was 1.7% and 2.9% in boys and girls respectively at 6 years; 2.0% and 3.8% at 7 years; 6.4% and 9.6% at 11 years; 6.5% and 9.6% at 14 years; 5.4% and 6.5% at 20 years; and 12.3% and 11.2% at 26 years. The risk of being overweight in adulthood was related to the degree of overweight in childhood and was about four in 10 for overweight 7-year-olds. Analysis of the data in the reverse direction showed that 7% and 13% respectively of 26-year-old overweight men and women had been overweight at the age of 7. These results suggest that there is no optimal age during childhood for the prediction of overweight in adult life and that excessive weight gain may begin at any time. Overweight children are more likely to remain overweight than their contemporaries of normal weight are to become overweight.
In the National Child Development Study (1958 cohort) information on their age at menarche and their weights and heights measured at 7, 11, and 16 years was available for 4427 girls. The distribution of age at menarche was not influenced by social class. Weight adjusted for height did not play an important part in the timing of sexual maturation of the girls in the study. Relative weight (weight expressed as a percentage of standard weight) at the ages of 7 and 11 years explained only 3.2%, and 4.9%, respectively of the variation in age at menarche, and changes in relative weight between these two ages accounted for 2%. Girls with early menarche were more likely to be overweight at ages 7, 11, and 16 years than those with late menarche, although early menarche was also reported by girls who were underweight or of average weight. These findings support the hypothesis that in well nourished populations the relation between menarche and body size is largely regulated by genetic factors and that nutrition is less important.
The purpose of this study was to investigate the relation between blood pressure at age 36, and birth weight and body mass index (BMI) in childhood, adolescence and adulthood.Prospective longitudinal survey over a period of 36 years in England, Scotland, and Wales.A nationally representative sample consisting of 3332 men and women born in one week in March 1946. Altogether 82% of these subjects had complete data for the present analysis.There was an inverse linear relation between birth weight and blood pressure at age 36. The relation between BMI and blood pressure at age 36 was initially inverse and became increasingly positive throughout life. Weight gain in childhood was positively associated with adult blood pressure, although less important than weight change in later life. The associations between blood pressure and birth weight, and blood pressure and adult BMI were independent, and together they accounted for no more than 4% of the variation in adult blood pressure. Both low birth weight (birth weight < or = 2.5kg) and high BMI at age 36 (BMI > 30kg/m2) were associated with hypertension (> 140/90mmHg), but the per cent population risk of hypertension attributable to low birth weight was less than 5%, and to high BMI less than 12%.Low birth weight and high BMI at age 36 were independently related to high blood pressure. A reduction in the percentage of low birthweight babies born in the fourth decade of this century would only have a negligible effect on the incidence of adult hypertension 30-40 years later.