Dietary measures of physical activity.

The relationships between cardiovascular fitness, body fatness, and the number of calories required to maintain stable body weight over a baseline period of three weeks were studied in 21 healthy obese males aged 20-44 years who participated in a controlled feeding experiment at the Division of Epidemiology (formerly the Laboratory of Physiological Hygiene) of the School of Public Health, University of Minnesota, in August 1980-June 1981. statistically significant relationships were found between the number of calories actually consumed per kg of body weight (kcal/kg) and body fatness (r = -0.79, p = 0.001), and number of calories consumer per kg of body weight and physical work capacity (VO2 max) (r = 0.76, p = 0.001). Using body fatness quartiles, the caloric intake per kg of body weight and VO2 max decreased progressively as body fatness increased through its four quartiles. These relationships were also seen when reported caloric intake from a three-day food record was used; however, the magnitude was attenuated. On the other hand, caloric intake unadjusted for body weight, whether actual or reported, was unrelated to both body fatness and VO2 max. To determine whether these relationships hold true for less obese subjects, the authors have also analyzed and compared their results with the data from previously reported feeding experiments done at the University of Minnesota. Correlations between body fat indices and actual caloric intake were similar for both studies. Therefore, the authors conclude that in these relatively young, healthy, and sedentary males with a wide range of body fatness and body weight, the observed relationships between caloric intake adjusted for body weight, body fatness and VO2 max reflect habitual physical activity. These data confirm epidemiologic observations of an inverse relationship between caloric intake per kg of body weight and body fatness, and provide a rationale for using caloric intake adjusted for body weight as a measure of long-term habitual physical activity. Thus, these data bolster the interpretation that an inverse relationship between caloric intake per kg of body weight and mortality reflects a positive health effect of long-term physical activity. This index may be particularly useful in large population studies.