Influence of obesity, physical inactivity, and weight cycling on chronic inflammation

Obesity prevalence continues to rise due to excessive caloric intake and sedentary behavior. Weight loss can be achieved through diet and/or exercise, but maintenance of a reduced weight is rare and relapse is prevalent. Repeated periods of weight loss and regain have been termed "weight cycling." It has been speculated that weight cycling may further increase the elevated disease risk common with weight gain, obesity, and physical inactivity. Alterations in adipose tissue with weight cycling may create a more hypoxic environment; hypoxic adipose tissue secretes leptin, a stimulus for macrophage activation and accumulation within adipose tissue. Hypoxic adipocytes and macrophages release pro-inflammatory cytokines into circulation. Elevated body weight and adiposity are linked to cardiovascular disease and type 2 diabetes via an inflammatory mechanism. Thus, it is reasonable to speculate that weight cycling causes a more profound change in chronic inflammation than sustained weight gain. The purpose of this review is to explore inflammatory consequences associated with weight cycling as they are related to sustained weight gain, obesity, physical inactivity as well as relative disease risk.