Relative Fat Mass (RFM) as Abdominal Obesity Criterion for Metabolic Syndrome

Aim: To assess whether Relative fat mass (RFM), a newly suggested obesity marker, can replace Waist circumference (WC) as the obesity criterion of metabolic syndrome.

Methods: Observational, cohort study, performed between 2008-2016 among patients who visited the Rambam Periodic Examinations Institute [RPEI]. We analyzed the differences in prevalence and characteristics of patients with metabolic syndrome using the traditional criteria and using RFM instead of WC as the obesity criterion.

Results: The study included 20,167 patients. Metabolic syndrome was diagnosed in 14% of the cohort (14.1% of men, 13.7% of women). The baseline characteristics of men and women with metabolic syndrome were significantly different. Women had higher proportions of abnormal WC (89.9% vs. 52.6%, p<0.001), men had significantly higher proportions of hypertension (59.1% vs. 43.6%, p<0.001), impaired fasting glucose (92.4% vs. 77.1%, p<0.001), hypertriglyceridemia [76.9% vs. 59.9%, p<0.001) and low HDL [89.3% vs. 79.8%, p<0.001). Using RFM as the obesity criterion of metabolic syndrome, 29.8% of the cohort diagnosed with metabolic syndrome (35% of men, 17.9% of women). There was no significant difference in the mean age (men 55.9±10.1 Vs. women 55.6±8.8, p=0.35), the prevalence of obesity (99.5% of men, 99.2% of women, p=0.16), impaired fasting glucose (72.4% of men, 71% of women, p=0.35) and hypertriglyceridemia (56.3% of men, 55.5% of women, p=0.66). Low HDL was more common among women (78.7% Vs. 72.3% of men, p<0.001), and hypertension among men (45.8% Vs. 38.4% of women, p<0.001), but the absolute differences were much smaller than using traditional criteria.

Conclusions: compared to WC, RFM as the obesity criterion of metabolic syndrome define a larger proportion of the population as suffering from metabolic syndrome, with much higher prevalence among men than women but with less intra-gender differences. Further prospective studies are needed to determine whether it predict better the cardiometabolic risk.