A new study published in the journal Nutrients suggests that body mass index (BMI) may place over a third of adults in the wrong weight category when compared to more precise measurements of body fat.
The cross-sectional study included over 1,300 men and women ranging from 18 to 98 years old from a general population in Northern Italy. The participants had their BMIs measured and were classified as underweight, normal weight, overweight, or obese. After the initial measurements, the participants underwent dual-energy X-ray absorptiometry (DXA) scans, which are known to give very precise measurements of body composition, including body fat percentage. The two weight status categorization methods, BMI and DXA scan, were then compared. BMI, which is based on weight and height, is a widely used health metric due to its accessibility and low expense. However, BMI cannot distinguish between fat and muscle mass, and it may incorrectly categorize many individuals with either very high or very low muscle mass. Accurate weight status categorizations are important for determining individual risk of many diseases, including heart disease, type 2 diabetes, and metabolic syndrome.
The comparison of BMI and DXA scan results showed that BMI miscategorized over one third of the individuals in the study. Among those who were classified as having obesity according to BMI, 34% were actually in the overweight category. Additionally, over half (53%) of those classified as overweight were in the wrong category. The normal weight range was more accurate based on BMI, with 78% agreement, while the underweight category had the largest discrepancy at 68.4%.
The authors of the study noted that BMI measurements appear to misclassify a large percentage of the general population, which could lead to overestimations of the prevalence of being underweight, overweight, or having obesity. These misclassifications could also lead to poor estimates of individual risk for heart disease and other chronic conditions, potentially delaying treatments and the implementation of preventive measures.
Sources: Nutrients, Science Daily
