Metabolically healthy obesity (MHO) is most common in women, younger adults, people with a BMI <35, and people of European ancestry.[1] Compared to people with metabolically unhealthy obesity (MUO), people with MHO have greater insulin sensitivity and insulin secretion, as well as less inflammation.[2][3] People with MHO also seem to have greater levels of physical activity and cardiorespiratory fitness.[4]
Evidence suggests that differences in body fat distribution — which is controlled by genetics, age, sex, and total body fat content — explain a large part of the difference in cardiometabolic risk between people with MHO and MUO.[5] Specifically, people with MHO have more subcutaneous fat and less visceral and skeletal muscle fat.[6][7]
People with MHO that consume excess calories display a much greater capacity for subcutaneous fat expansion via the formation of new fat cells than people with MUO who primarily accommodate excess calories by increasing the size of existing fat cells.[5][8] Subcutaneous fat expansion via new fat cell formation prevents fat deposition into visceral fat and results in smaller fat cells, attenuating the negative metabolic effects of obesity.