CONTRIBUTION OF DIETING TO THE INVERSE ASSOCIATION BETWEEN ENERGY-INTAKE AND BODY-MASS INDEX

Objective: To examine the association of energy and % energy from fat with body mass index (BMI) and determine if self-reported dieting alte red observed associations. Design: Dietary intake data based on dietar y recalls from four nonconsecutive days over a 1 year period were exam ined relative to BMI. The relation between energy intake and % energy from fat and BMI was examined by linear regression analysis. Subjects: The sample included 1854 free-living women aged 19-50 years who parti cipated in the 1985-6 Continuing Surveys of Food Intakes by Individual s conducted by the United States Department of Agriculture, Results: R eported energy intake was inversely associated with BMI (regression co efficient (beta) = -0.001 24, standard error (s.e.) = 0.000 31). Contr olling for low energy dieting alone reduced the inverse energy intake- BMI association by approximately 20% (beta = -0.001 00, s.e. = 0.000 3 1), compared to reductions of 16%, 13% and 10%, respectively, when hea lth status, age and education were added individually to the energy in take - BMI linear regression. Physical activity, smoking status, % ene rgy from fat and report of low fat dieting did not reduce the energy i ntake - BMI association. Controlling for nondietary factors related to BMI and potentially influencing energy intake reduced the inverse ene rgy intake - BMI association by similar to 22% (beta = -0.000 97, s.e. = 0.000 25). Further adjustment for low energy dieting on day 1 reduc ed the inverse energy intake - BMI association by 40% (beta = -0.000 7 4, s.e. = 0.000 26), suggesting that intermittent energy restriction w as a significant factor in the reduced energy intake reported among ov erweight women. Percent energy from fat was not associated with BMI (b eta = 0.049, s.e. = 0.025, P = 0.055). Exclusion of 37 women reporting poor health status further attenuated the inverse association between energy intake and BMI (beta = -0.000 64, s.e. = 0.000 26), while it s trengthened the previously non-significant positive association betwee n % energy from fat and BMI (beta = 0.062; s.e. = 0.024). Conclusion: Intermittent energy restriction appeared to be a significant factor in the reduced energy intake reported among overweight women in this sam ple. Adequate assessment of energy expenditure is required to correctl y interpret the association of energy intake to body weight. Sponsorsh ip: National Cancer Institute, National Institutes of Health. Descript ors: body weight, dieting, energy, fat, obesity, physical activity