Background: Despite its many shortcomings, body mass index (BMI) is the most widely used screening tool for obesity, in part, because of its practicality. Other more physiologic measurements of obesity are based on body fat (BF). However, the correlation between BMI and BF has not been well-characterized, especially in patients with coronary heart disease (CHD).
Methods: We retrospectively studied 581 patients with CHD following major CHD events, who were divided according to BMI (calculated as weight divided by height squared), based on the World Health Organization standard cutoff points (underweight [<18.5 kg/m], normal [≥18.5 and <25 kg/m], overweight [≥25 and <30 kg/m], and obese [≥30 kg/m]). Second, the population was divided according to BF, on the basis of the age- and gender-adjusted Gallagher BF classification into underweight, normal, overweight, and obese categories.
Results: Body mass index and percent BF correlated significantly (r = 0.60; P < .0001) and classified patients in the same category in about 59% of patients. In approximately 27% of the sample, BMI underestimated BF, while in about 14% of cases BMI overestimated BF. The relationship between BMI and BF was influenced by age, gender, and BMI itself.
Conclusions: Even though a correlation exists between BMI and BF, they frequently classify individuals differently in a population of CHD patients. When defining overweight/obesity, care must be taken when using a crude screening tool such as BMI. While it is not expected for all clinicians to add BF assessments within routine patient assessments, the results of this study may be helpful to guide clinicians and researchers who are considering different aspects of body composition.