RESUMEN
BACKGROUND: Few data exist on the energy cost of specific activities in children. The influence of body weight on the energy cost of activity when expressed as metabolic equivalents (METs) has not been vigorously explored. OBJECTIVE: To provide MET data on five specific activities in 12-y-old girls and to test the hypothesis that measured MET values are independent of body weight. SUBJECTS AND METHODS: In 17 12-y-old girls, resting metabolic rate (RMR) and the energy expended while sitting, standing, walking on a flat treadmill at 3.2 and at 4.8 km/h, and walking on a treadmill at a 10% incline at 4.8 km/h were measured using indirect calorimetry. MET values were calculated by dividing the energy expenditure of an activity by the subject's RMR. The influence of body weight was assessed using simple linear regression. RESULTS: The observed METs were more consistent with published values for similar activities in adults than those offered for children. Body weight was a statistically significant predictor of the MET of all three walking activities, but not the MET of sitting or standing. Body weight explained 25% of the variance in the MET value for walking at 3.2 km/h, 39% for walking at 4.8 km/h, and 63% for walking at a 10% incline at 4.8 km/h. CONCLUSION: METs for the three walking activities were not independent of body weight. The use of average MET values to estimate the energy cost of these three activities would result in an underestimation of their energy cost in heavier girls and an overestimation in lighter girls. These results suggest that the estimation of total energy expenditure from activity diary, recall, and direct observation data using average MET values may be biased by body weight.
Asunto(s)
Peso Corporal/fisiología , Metabolismo Energético/fisiología , Actividad Motora/fisiología , Metabolismo Basal/fisiología , Niño , Prueba de Esfuerzo , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Estudios ProspectivosRESUMEN
BACKGROUND: Overweight adults are at an increased risk of developing numerous chronic diseases. METHODS: Ten-year follow-up (1986-1996) of middle-aged women in the Nurses' Health Study and men in the Health Professionals Follow-up Study to assess the health risks associated with overweight. RESULTS: The risk of developing diabetes, gallstones, hypertension, heart disease, and stroke increased with severity of overweight among both women and men. Compared with their same-sex peers with a body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meters) between 18.5 and 24.9, those with BMI of 35.0 or more were approximately 20 times more likely to develop diabetes (relative risk [RR], 17.0; 95% confidence interval [CI], 14.2-20.5 for women; RR, 23.4; 95% CI, 19.4-33.2 for men). Women who were overweight but not obese (ie, BMI between 25.0 and 29.9) were also significantly more likely than their leaner peers to develop gallstones (RR, 1.9), hypertension (RR, 1.7), high cholesterol level (RR, 1.1), and heart disease (RR, 1.4). The results were similar in men. CONCLUSIONS: During 10 years of follow-up, the incidence of diabetes, gallstones, hypertension, heart disease, colon cancer, and stroke (men only) increased with degree of overweight in both men and women. Adults who were overweight but not obese (ie, 25.0 < or = BMI < or = 29.9) were at significantly increased risk of developing numerous health conditions. Moreover, the dose-response relationship between BMI and the risk of developing chronic diseases was evident even among adults in the upper half of the healthy weight range (ie, BMI of 22.0-24.9), suggesting that adults should try to maintain a BMI between 18.5 and 21.9 to minimize their risk of disease.