The women enrolled in the study were slightly younger than the men (38.5 ± 14 years vs 39.2 ± 13.3 years), but this difference was not statistically significant (t = 0.201, p = 0.841).
On average, the men recorded higher body weight, waist circumference and BFMI values than the women, while the women had a higher %BF and metabolic syndrome risk (Table ). Body fat percentage measured by DXA was significantly linearly related to that measured by BIA (rPearson = 0.827, p < 0.0001).
Summary of statistics by sex (mean values and standard deviations in square brackets).
According to the classification based on BMI, 6.3% of subjects were underweight, 52.4% were normal weight, 30.2% were overweight, and 11.1% were obese. Abdominal adiposity was not increased in 63.5% of subjects, increased in 11.1%, and substantially increased in 25.4%. Total body fat, considered alone, was low in 3.2% of subjects, normal in 49.2%, increased in 19.0%, and high in 28.6%. Metabolic syndrome risk related to %BF was low in 7.1% of subjects, normal in 37.5%, increased in 21.4%, and high in 33.9%. BFMI was low in 3.6% of subjects, normal in 42.9%, increased in 32.1%, and high in 21.4%.
Metabolic syndrome risk was the only criterion to show significant gender-related differences (χ2 = 9.430; p = 0.024): greater percentages of the women compared to the men showed a high metabolic syndrome risk (37.1% vs 28.6%), and a low and normal metabolic syndrome risk (8.6% vs 4.8% and 45.7% vs 23.8%, respectively); conversely, a greater proportion of the men had an increased metabolic syndrome risk (42.9% vs 8.6%).
Agreement between the BMI categories and the other classification criteria categories varied (Table ). The most notable discrepancy emerged in the underweight and overweight categories. Of the subjects classed as underweight on the basis of BMI, 75% had normal %BF and metabolic syndrome risk values, and none had an increased waist circumference. In the BMI normal weight subjects, increased abdominal fat was found in 9.1%, increased %BF in 15.2%, and increased metabolic syndrome risk in 20%; a high %BF was found in 6.1% of the normal weight subjects and a high metabolic syndrome risk in 16.7%. In the overweight subjects, a marked discrepancy emerged between the BMI and the adiposity indices: more than 50% of the subjects had a high %BF and metabolic syndrome risk and just under 50% high abdominal fat. In the subjects rated as obese on the basis of their BMI, there was good agreement between all the criteria.
Agreement between the BMI categories and the other classification criteria categories expressed as percentage values. The values in bold represent the main diagonal of the agreement matrix.
Comparing the BMI with the BFMI categories, 75% of the underweight subjects had a normal fat status. In the BMI normal weight category, 30% of the subjects were "overfat" according to the BFMI, while in the overweight category only 6.7% of subjects had a normal fat status and 40% had a severely "overfat" status. There was good agreement between BMI and BFMI in the obese subjects. Overall, the BMI showed good agreement with BFMI (tau-b Kendall = 0.722, p < 0.001) and waist circumference (abdominal fat) (tau-b Kendall = 0.704, p < 0.001). The level of agreement between the various BMI categories and the %BF and metabolic syndrome risk categories was moderate (tau-b Kendall = 0.672, p < 0.001 and tau-b Kendall = 0.563, p < 0.001 respectively).
The percentages of subjects for whom weight loss treatment would be recommended and strongly recommended, on the basis of each criterion, are summarised in figure . The proportion of subjects for whom clinicians would recommend weight loss on the basis of their BMI (41.3%) was not significantly different from the proportions in whom it would be recommended on the basis of %BF (p = 0.344) and abdominal fat (p = 0.508). Conversely, a significant difference emerged in relation to the criteria metabolic syndrome risk (p = 0.022) and BFMI (p = 0.021). The picture changes when analysing the proportion of subjects for whom weight loss would be strongly recommended, with the proportion identified on the basis of BMI (11.1%) differing significantly from the proportion identified by abdominal fat (p = 0.004), %BF (p = 0.003), and metabolic syndrome risk (p = 0.002). Instead, no significant difference was found between the proportions of subjects whom clinicians, on the basis of BMI versus BFMI, would be strongly urged to lose weight (p = 0.125).
Figure 1 Weight loss treatment recommendations for each criterion. Percentage of subjects for whom weight loss would be recommended, including those for whom it would be strongly recommended, on the basis of the different criteria: BMI (Body Mass Index), WC (waist (more ...)