The Effect of Dietary Choice on Body Size and Insulin Resistance in Children: a Longitudinal Study.

Rates of childhood obesity are increasing but few longitudinal studies have examined the contribution of dietary choice. We examined the impact of dietary choice on the development of obesity and insulin resistance in healthy young children from the EarlyBird Study (140 boys, 111 girls). The following measures were made annually from 5 to 9 years: BMI(sds), sum of 5 skinfolds (SSF), fasting glucose and insulin to calculate insulin resistance (HOMAIR); % abdominal fat by Dexa at 9y. Food frequency questionnaires were completed annually by a parent and three variables calculated (number of days consumed per week expressed as a percentage of maximum possible frequency): HS (composite of 6 high sugar foods and drinks including cola), HF (11 high fat foods), FV (3 foods: fruit, vegetables, salad). No food was assigned to more than one group. 1. Dietary reports were consistent year-on-year (in each food group year-on-year correlation r=0.3-0.5, p<0.001). 2. From 5-9 years, BMI(sds) rose (0.34 to 0.48, p=0.007); SSF rose (3.98cm to 5.62cm, p<0.001) yet frequency of HF fell (25.5% to 22.1%, p<0.001) and HS fell 54.4% to 49.3%, p<0.001). 3. Frequency of FV remained unchanged (11.4% to 11.6%, p=0.5) and was not associated with BMI or SSF in either gender, or with HOMA-IR in boys (r<0.1). In girls at 5y and 6y, FV was positively associated with HOMA-IR (r=0.21, 0.22, p<0.05). 4. Frequency of HF correlated with HS foods at each age (r=0.2-0.6, p<0.01). 5. BMI at 8 and 9y was inversely related to HF in both genders (r=-0.18 to -0.28, p<0.05). 6. BMI and SSF were inversely related to HS at every age, significantly so in girls (r= -0.18 to -0.29, p<0.05). 7. HS at 5y predicted lower BMI, SSF, HOMA-IR and % abdominal fat at 9y in girls (r=-0.26, -0.30, -0.24, -0.26, p<0.05 respectively). Parental reports regarding children's dietary habits are consistent year-on-year. Body size appears unrelated to frequency of consumption of healthy foods. Unexpectedly, children whose diets are highest in fat and sugar seem to be the leanest and metabolically healthiest. This could be due to parental misreporting, but it is also possible that meal size is more important than content in childhood obesity. [ABSTRACT FROM AUTHOR]