Is obesity an inflammatory disease?

Background. Most obese individuals have elevated concentrations of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), markers of inflammation closely associated with diabetes, hypertension, and stroke. Hypothesis. Obesity is a low-grade inflammatory disease, and Roux-en-Y gastric bypass (RYGB) reduces biochemical markers of inflammation and modifies gene expression in hypothalamic food intake/energy-related nuclei and subcutaneous abdominal fat (SAF). Methods. Obesity was induced in 24 3-week-old Sprague Dawley pups fed a high-energy diet (HED). Three groups (n = 8/group) were studied: RYGB, sham-operated pair-fed, and sham-operated ad libitum HED. Controls were nonobese rats fed chow (n = 6). Rats were killed 10 days after operation, and blood was collected to measure corticosterone and SAF and mesenteric fat to measure IL-6, TNF-α, and corticosterone. Total mRNA from arcuate nucleus and SAF purified for gene expression profiling. Data were analyzed with analysis of variance, Mann-Whitney test, and t test. Results. Before operation, the body weight of the obese groups was 493 ± 7 g and control = 394 ± 12g. The 10-day postoperative weight was RYGB = 417 ± 21 g, pair-fed = 436 ± 14 g, and ad libitum HED = 484 ± 15 g. Mesenteric and SAF weight decreased in RYGB. Mesenteric/SAF ratio of IL-6, TNF-α, corticosterone, and gene profiling showed decrease of inflammation after RYGB. Conclusion. Gastric bypass reduces biochemical markers of inflammation, suggesting that obesity is an inflammatory condition. (Surgery 2003;134:329-35.)