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ObjectiveTo compare body composition parameters estimated by air displacement plethysmography (ADP) to dual x-ray absorptiometry (DXA) in body mass index (BMI) classifications that include extremely obese (BMI≥40.0kg/m2), and to examine if differences between analyses were influenced by BMI.Design and MethodsFat free mass (FFM,kg), fat mass (FM,kg) and body fat (BF,%) were analyzed with both technologies.ResultsAll outcome measures of ADP and DXA were highly correlated (r≥0.95,P<0.001 for FFM, FM and BF), but Bland-Altman analyses revealed significant bias (P<0.01 for all). ADP estimated greater FFM and lower FM and BF (P<0.01 for all). BMI explained 27% of the variance in differences between FFM measurements (P<0.001), and 37% and 33% of the variances in differences between FM and BF measurements, respectively (P<0.001 for both). Within normal weight and overweight classifications, ADP estimated greater FFM and lower FM and BF (P<0.001 for all), but the opposite occurred within the extremely obese classification; ADP estimated lower FFM and greater FM and BF (P<0.05 for all).ConclusionsBody composition analyses by the two technologies were strongly congruent, but systematically different and influenced by BMI. Caution should be taken when utilizing ADP to estimate body composition parameters over a wide range of BMI classifications that include extremely obese.

Background Aging-related disease risk is exacerbated by obesity and physical inactivity. It is unclear how weight loss and increased activity improve risk in older adults. We aimed to determine the effects of diet-induced weight loss with and without exercise on insulin sensitivity, VO2peak, body composition, and physical function in older obese adults. Methods Physically inactive older (68.6 ± 4.5 years) obese (BMI 37.4 ± 4.9 kg/m 2) adults were randomized to: Health education control (HEC; n=25); Diet-induced weight loss (WL; n=31); or Weight loss and exercise (WLEX; n=28) for 6 months. Insulin sensitivity was measured by hyperinsulinemic euglycemic clamp, body composition by DXA and MRI, strength by isokinetic dynamometry, and VO2peak by graded exercise test. Results WLEX improved (p&lt;0.05) peripheral insulin sensitivity (+75 ± 103%) vs. HEC (+12 ± 67%); WL (+36 ± 47%) vs. HEC did not reach statistical significance. WLEX increased VO2peak (+7 ± 12%) vs. WL (-2 ± 24%), and prevented reductions in strength and lean mass induced by WL (p&lt;0.05). WLEX decreased abdominal adipose tissue (-16 ± 9%) vs. HEC (-3 ± 8%) and intermuscular adipose tissue (-15 ± 13 %) vs. both HEC (+9 ± 15%) and WL (+2 ± 11%) (p&lt;0.01). Conclusions Exercise with weight loss improved insulin sensitivity and VO2peak, decreased ectopic fat, and preserved lean mass and strength. Weight loss alone decreased lean mass and strength. Older adults intending to lose weight should perform regular exercise to promote cardiometabolic and functional benefits, which may not occur with calorie restriction-induced weight loss alone.

The nitrate-nitrite-NO pathway regulates NO synthase–independent vasodilation and NO signaling. Ingestion of inorganic nitrite has vasodilatory and blood pressure–lowering effects. Preclinical studies in rodent models suggest there may be a benefit of nitrite in lowering serum triglyceride levels and improving the metabolic syndrome. In a phase 2 study, we evaluated the safety and efficacy of chronic oral nitrite therapy in patients with hypertension and the metabolic syndrome. Twenty adult subjects with stage 1 or 2 hypertension and the metabolic syndrome were enrolled in an open-label safety and efficacy study. The primary efficacy end point was blood pressure reduction; secondary end points included insulin-dependent glucose disposal and endothelial function measured by flow-mediated dilation of the brachial artery and intima-media diameter of the carotid artery. Chronic oral nitrite therapy (40 mg/3× daily) was well tolerated. Oral nitrite significantly lowered systolic, diastolic, and mean arterial pressures, but tolerance was observed after 10 to 12 weeks of therapy. There was significant improvement in the intima-media thickness of the carotid artery and trends toward improvements in flow-mediated dilation of the brachial artery and insulin sensitivity. Chronic oral nitrite therapy is safe in patients with hypertension and the metabolic syndrome. Despite an apparent lack of enzymatic tolerance to nitrite, we observed tolerance after 10 weeks of chronic therapy, which requires additional mechanistic studies and possible therapeutic dose titration in clinical trials. Nitrite may be a safe therapy to concominantly improve multiple features of the metabolic syndrome including hypertension, insulin resistance, and endothelial dysfunction. Registration— URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01681810.

Objective: To determine effects of physical activity (PA) with diet-induced weight loss on energy metabolism in adults with severe obesity. Methods: Adults with severe obesity (n 5 11) were studied across 6 months of intervention, then compared with controls with less severe obesity (n 5 7) or normal weight (n 5 9). Indirect calorimetry measured energy metabolism during exercise and rest. Markers of muscle oxidation were determined by immunohistochemistry. Data were presented as medians. Results: The intervention induced 7% weight loss (P 5 0.001) and increased vigorous PA by 24 min/wk (P 5 0.02). During exercise, energy expenditure decreased, efficiency increased (P 0.03), and fatty acid oxidation (FAO) did not change. Succinate dehydrogenase increased (P 5 0.001), but fiber type remained the same. Post-intervention subjects' resting metabolism remained similar to controls. Efficiency was lower in post-intervention subjects compared with normal-weight controls exercising at 25 W (P 0.002) and compared with all controls exercising at 60% VO 2peak (P 0.019). Resting and exercise FAO of post-intervention subjects remained similar to adults with less severe obesity. Succinate dehydrogenase and fiber type were similar across all body weight statuses. Conclusions: While metabolic adaptations to PA during weight loss occur in adults with severe obesity, FAO does not change. Resulting FAO during rest and exercise remains similar to adults with less severe obesity.