Expression of Metabolic Syndrome in Women with Severe Obesity

Abstract

Background: The prevalence of metabolic syndrome (MetS) generally rises with increasing adiposity, but tends to plateau at the highest levels of body mass index (BMI) with some individuals, even with severe obesity, expressing few or no components of MetS. We examined factors associated with the expression of MetS in severely obese women participating in a large observational study.

Methods: Anthropometrics, including Heath equation-adjusted bioimpedance-determined fat-free mass (FFM) and fat mass (FM), lipids and related laboratory measurements, resting energy expenditure (REE), and respiratory quotient (RQ), were studied in 949 women with severe obesity.

Results: Even though the mean BMI was 45.7 kg/m² and all participants met MetS criteria for increased waist circumference, 30% of subjects did not have MetS. Unadjusted FM (P = 0.0011), FFM (P < 0.0001), and REE (P < 0.0001) were greater in the women with MetS. Surprisingly, in multivariate logistic regression FFM was positively associated with MetS (P = 0.0002), while FM was not (P = 0.89). Moreover, FFM, not FM, was significantly associated with all five components of MetS except for triglyceride levels. REE and RQ were higher in those with MetS, and REE was strongly associated with multiple components of MetS.

Conclusions: In women with severe obesity, higher FFM and REE were paradoxically associated with increased rather than decreased risk of MetS, while FFM-adjusted FM was unrelated to MetS.

Keywords: insulin; liver enzymes; metabolic syndrome; obesity.

FIG. 1.

Association of MetS with FFMI and FMI. For purposes of illustration, prevalence of MetS by tertiles of FFMI and FMI are shown. For analysis, a continuous logistic model adjusting for age, higher FFMI was strongly associated with increased risk of MetS (P = 0.0004), while FMI was not (P = 0.79). FFM, fat-free mass; FM, fat mass; FFMI, FFM index; FMI, FM index; MetS, metabolic syndrome.

FIG. 2.

Association of FFM and FM with MetS and related factors. FM and FFM were considered independent variables (along with age and height) in logistic regression models to predict presence/absence of variables shown along the vertical axis. Shown on the horizontal axis are values for the standardized β-coefficients for FM and FFM obtained from each of these logistic regression models. Cutpoints for variables other than MetS factors represent median values except for GGTP whose cutpoint was the upper limit of normal. P-values are designated with the following symbols: *<0.05, ^†<0.01, ^‡<0.001, ^§<0.0001. GGTP, gamma-glutamyl transpeptidase.

FIG. 3.

Resting energy expenditure is higher in women with severe obesity who have MetS. Shown are least square means and SE from analysis of covariance, adjusted for age, FM, and FFM (all with P < 0.0001). SE, standard error.