Body mass index and its correlates in 1,212 ultramarathon runners: baseline findings from the ULTRA study.

Background: Little is known about the sociodemographics and lifestyle behaviors of ultramarathon runners, and the effects of these characteristics on body weight and body mass index (BMI).

Methods: We cross-sectionally analyzed baseline data of 1212 ultramarathoners on sociodemographics, lifestyle behaviors and BMI from the initial 12-month enrollment period in a longitudinal observational study.

Results: The ultramarathoners were mostly middle-aged men who were more educated, more likely to be in a stable relationship, and more likely to use over-the-counter vitamins/supplements than the general population. They appear to gain less body weight with advancing age than the general population. Factors with the greatest effect on current BMI were BMI at 25 years of age and sex, which explained 48% and 3% of the variance. Negligible, but statistically significant direct relationships, with BMI were observed for age, work hours per week, television watching hours per week, and composite fat consumption frequency score. Negligible, but statistically significant inverse relationships, with BMI were observed for running distance during the prior year, and composite fruit and vegetable consumption frequency score.

Conclusions: While lifestyle decisions were found to impact BMI within this group of ultramarathoners, BMI at age 25 was the strongest predictor of current BMI.