Torstveit, M. K., & Sundgot-Borgen, J. (2012). Are under- and over-weight female elite athletes thin and fat? A controlled study. Medicine & Science in Sports & Exercise, 44, 949-957.

This study related the body mass index (BMI) to body fat percentage in female elite athletes from different sports and non-athletic controls. It determined some characteristics of athletes with unhealthy low and high body fat values. The study was conducted in three phases: 1) screening with a detailed questionnaire, 2) body composition measurement (dual-energy x-ray absorptiometry), and 3) clinical interview. All female elite athletes (aged 13-39 years, N = 938) representing national teams at the junior or senior level and an age group-matched randomly selected population-based control group (N = 900) were invited to participate. A stratified random sample was invited to participate in parts 2 and 3 of the investigation. A total of 186 athletes and 145 controls participated in all three study phases.

Among the athletes were those within a normal range of BMI values (N = 150; BMI 18.5-24.9), 2.0% were classified with low body fat levels (<12%), and 6.7% were classified with obese body fat levels (>33%). The median value for the entire group was 24.3% body fat. For the controls, normal BMI values were in 96 Ss, none was classified with low body fat levels, and 50% were classified with obese body fat levels (median = 33.1%). The correlation between BMI and body fat percentage was 0.671 for the athletes and 0.813 for the controls. Both under- and over-fat athletes self-reported menstrual dysfunction, stress fractures, history of weight fluctuation, and use of pathogenic weight control methods and were diagnosed with clinical eating disorders and/or low bone density.

Implication. The body mass index (BMI) is not a valid measure for assessing or monitoring body composition in female elite athletes. It should be used carefully in female non-athletes.

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