Objective: To compare the value of body fat mass (%FM) to indirect measures of general (body mass index (BMI)) and central adiposity (waist circumference (WC); waist-to-height ratio (WC/ht)) for the prediction of overweight-and obesity-related metabolic risk in a study population with a high prevalence of metabolic syndrome (MSX). Methods: BMI, WC, WC/ht, body composition (by air-displacement plethysmography) and metabolic risk factors: triglycerides, cholesterol, HDL-cholesterol (HDL-C), uric acid, systolic blood pressure (BPsys), insulin resistance by homeostasis model assessment (HOMA-IR) and C-reactive protein (CRP) were measured in 335 adults (191 women, 144 men; mean age 53 713.9 years, prevalence of MSX 30%). Results: When compared with BMI and WC, %FM showed weaker associations with metabolic risk factors, except for CRP and BPsys in men. In women, HDL-C and HOMA-IR showed the closest correlations with BMI. For all other risk factors, WC or WC/ht were the best predictors in both sexes. Differences in the strength of correlations between an obesity index and different risk factors exceeded the differences observed between all obesity indices within one risk factor. In stepwise multiple regression analyses, WC/ht was the main predictor of metabolic risk in both sexes combined. However, analysis of the area under receiver operating characteristic curves for prediction of the prevalence of X2 component traits of the MSX revealed a similar accuracy of all obesity indices. Conclusions: At the population level, measurement of body FM has no advantage over BMI and WC in the prediction of obesityrelated metabolic risk. Although measures of central adiposity (WC, WC/ht) tended to show closer associations with risk factors than measures of general adiposity, the differences were small and depended on the type of risk factor and sex, suggesting an equivalent value of methods.
Objective: We aimed to define the effect of L-3,5,3 0 -tri-iodothyronine (T 3 ) on metabolic adaptation in underweight patients with anorexia nervosa (AN) as well as during weight gain. Methods: This involved clinical investigation of 28 underweight patients with AN, who were compared with 49 normal-weight controls. A subgroup of 17 patients was followed during weight gain. Resting energy expenditure was measured by indirect calorimetry. Body composition was measured by anthropometry as well as bioelectrical impedance analysis. Energy intake (EI) was assessed by a 3-day dietary record. Plasma concentrations of thyroid hormones (thyroxine (T 4 ), T 3 and thyrotropin (TSH)) were analyzed by enzyme immunoassays. Results: When compared with normal-weight women, underweight patients with AN had reduced fat mass (FM) (271.3%), fat-free mass (FFM) (2 13.1%), resting energy expenditure (REE) (221.8%), T 3 -(2 33.4%) and T 4 -concentrations (2 19.8%) at unchanged TSH. REE remained reduced after adjustment for FFM (2 24.6%). T 3 showed a close association with REE. This association remained after adjustment of REE for FFM. Treatment of underweight AN patients resulted in a mean weight gain of 8.3 kg. This was mainly explained by an increase in FM with small or no changes in FFM. REE and T 3 also increased (þ9.3% and þ 33.3% respectively) at unchanged TSH and T 4 . There was a highly significant association between weight gain-induced changes in T 3 and changes in adjusted REE (r ¼ 0.78, P , 0.001, based on Pearson's correlation). An increase in plasma T 3 concentrations of 1.8 pmol/l could explain an increase in REE of 0.6 MJ/day (that is, a 32% increase in T 3 was associated with a 13% increase in REE). Conclusions: Our data provide evidence that the low T 3 concentrations add to metabolic adaptation in underweight patients with AN. During weight gain, increases in T 3 are associated with increases in REE, which is independent of FFM. Both results are evidence for a physiologic role of T 3 in modulation of energy expenditure in humans.
Leptin contributes to metabolic adaptation in women with AN. The leptin response is associated with weight gain.
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