BMI from 3–6 y of age is predicted by TV viewing and physical activity, not diet

Abstract

OBJECTIVE: To investigate whether, diet, physical activity, sedentary behavior or television (TV) viewing predicted body mass index (BMI) among 3-7-y-old children. DESIGN: A triethnic cohort of 3-4-y-old children was followed for 3 y from 1986 to 1989. MEASUREMENTS: BMI was assessed at the beginning and end of each measurement year. Heart rate monitoring and observation were used to assess physical activity. Diet (calories, % calories from fat and carbohydrate), sedentary behavior and TV viewing were assessed by direct observation in each year. A repeated measures regression analysis with year as a factor and BMI at the end of each year as dependent variables was run. Nonsignificant variables were removed in a stepwise backward deletion process and significant interactions graphed. RESULTS: The interactions between minutes of TV viewing per hour and study year and minutes of physical activity per hour and study year were significant (Po0.05). There were also significant main effects for TV viewing, physical activity and BMI from the beginning of the study. The model accounted for 65% of the variance in BMI across the three study years. Plotting the significant interactions demonstrated that physical activity was positively associated with BMI in year 1, and negatively associated in years 2 and 3 with a stronger negative relationship in year 3 than 2. TV viewing became positively associated with BMI during the third study year. CONCLUSION: Physical activity and TV viewing were the only significant predictors (other than baseline BMI) of BMI among a triethnic cohort of 3-4-y-old children followed for 3 y with both physical activity (negatively associated) and TV viewing (positively associated) becoming stronger predictors as the children aged. It appears that 6 or 7 y is a critical age when TV viewing and physical activity may affect BMI. Therefore, focusing on reducing time spent watching television and increasing time spent in physical activity may be successful means of preventing obesity among this age group.

Physical activity and sedentary behavior: a review of longitudinal studies of weight and adiposity in youth

“…97 A positive relationship between television and BMI was also seen in preschool (3-4 y) children followed for 3 y. 66 Horn et al 78 reported a significant relationship between TV and adiposity in girls, but not boys; Mohawk girls (age 7.5) who watched 44.5 h/week of TV had graded increases in subscapular skinfold thickness over 2 y. Finally, in a study of young US children (age 5 y), those who watched more TV had higher BMI at age 9, but only if they were from families with no overweight parents.…”

“…Only five of the studies used objective measures of physical activity. 35,48,[65][66][67] The others relied on self-reported measures, either by the children themselves, 61,[68][69][70][71] by their parents, [72][73][74][75][76][77] or by a combination thereof. 78 In the Framingham Children's Study, children wore accelerometers for up to 5 days twice per year.…”

“…Among Native American second-grade children in the Pathways Project, activity based on accelerometry was associated with lower adiposity among children of normal weight status, but with higher adiposity and BMI among overweight children. 65 In 3-4-y-old children from Texas, heart rate telemetry from multiple days was used to assess physical activity over 3 y. Repeated-measures regression analysis showed that physical activity was positively associated with BMI in year 1 of follow-up, but negatively associated in years 2 and 3, 66 an interaction which the researchers interpreted as developmental differences emerging at age 6-7. Kettaneh et al 67 used 7 days of data from pedometers to classify French children as having low or high activity levels.…”

“…66,73,[75][76][77][78]81,96,97 Of the studies with younger subjects, most reported positive associations between television viewing and adiposity. 66,77,78,81,96,97 Each additional hour of TV watched by Australian children at age 6 was associated with a 40% increased odds of overweight at age 8. Associations remained significant after adjusting for birth weight, maternal BMI, maternal smoking, and children's PAL.…”

Beyond-brand effect of television food advertisements on food choice in children: the effects of weight status

“…Moreover, TV viewing behaviour predicts later adiposity, suggesting a causative role (9,11,12) . While this relationship is in part mediated by exercise (11) , much research has also demonstrated that TV viewing is also associated with specific differences in food intake and diet.…”