Energy from fat is associated with obesity in U.S. men: results from the Prostate Cancer Prevention Trial.

BACKGROUND

Diets high in fat have been proposed as one cause of obesity, primarily because fat is more energy-dense than other macronutrients. However, the literature on fat consumption and human obesity is inconclusive. This research examines associations between dietary fat intake and obesity in men participating in the Prostate Cancer Prevention Trial.

METHODS

Data in this cross-sectional study are from 15,266 men (55-79 years) who completed questionnaires on usual diet, physical activity, and health-related characteristics. Height and weight were collected by clinic personnel. Obesity was defined as body mass index (BMI) greater than or equal to 30 kg/m2.

RESULTS

In this healthy cohort, 23.3% were obese. Younger age, a sedentary lifestyle, lower education, and black race were positively associated with obesity (all P < 0.001). Using two statistical approaches, both total energy and energy from fat, but not total energy from other macronutrients, increased linearly and significantly with increasing BMI. Mean fat intake increased from 691 kcal (31.4% energy) among normal-BMI men to 797 kcal (34.3% energy) among the obese (P for trend <0.001). After controlling for demographic and health-related characteristics in regression models, BMI increased by 0.53 and 0.14 kg/m(2) for every 500 kcal of fat and total energy consumed, respectively. Energy underreporting, based on estimated basal metabolic rate and physical activity, was fourfold higher among obese compared to normal-weight men.

CONCLUSIONS

In this large cohort of healthy older men, energy from fat was associated with obesity, suggesting that high-fat dietary patterns are contributing to the high rates of obesity in U.S. men.