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Objective Weight regain after weight loss is common, and there is evidence to suggest negative effects on health because of weight cycling. This study sought to investigate the impact of weight regain in formerly obese mice on adipose tissue architecture and stromal cell function. Methods A diet-switch model was employed for obesity induction, weight loss, and weight regain in mice. Flow cytometry quantified adipose tissue leukocytes in adipose tissue. Liver and adipose tissue depots were compared to determine tissue-specific effects of weight cycling. Results Epididymal white adipose tissue of formerly obese mice failed to expand in response to repeat exposure to high-fat diet and retained elevated numbers of macrophages and T cells. Weight regain was associated with disproportionally elevated liver mass, hepatic triglyceride content, serum insulin concentration, and serum transaminase concentration. These effects occurred despite an extended 6-month weight loss cycle and they demonstrate that formerly obese mice maintain durable alterations in their physiological response to weight regain. Conditioned media from epididymal adipose tissue of formerly obese mice inhibited adipogenesis of 3T3-L1 preadipocytes, suggesting a potential mechanism to explain failed epididymal adipose tissue expansion during weight regain. Conclusions Metabolic abnormalities related to defects in adipose tissue expansion and ongoing dysfunction manifest in formerly obese mice during weight regain.

Objective Obesity has been associated with markers of increased systemic inflammation in both human and animal studies. Increased inflammation is linked to metabolic and cardiovascular disease. The objective of this study was to evaluate the association between percentile body fat and inflammation in a nationally representative sample of US children. Methods: 6,950 children 8-18 years of age between 1999 and 2004 were studied. Measurement of body fat percentage was measured by dual-energy X-ray absorptiometry scan and converted to an age- and sex-adjusted percentile. The main outcome measures were abnormal c-reactive protein (CRP > 1.0 mg/dl) and absolute neutrophil count (ANC > 6,600). Results Children with higher levels of body fat (≥70th percentile) had a higher odds of having elevated CRP (OR 2.88-10.69) and elevated ANC (OR 2.14-3.24) compared with children with body fat