Normal Weight Obesity

Normal weight obesity is the condition of having normal body weight, but with a high body fat percentage, leading to some of the same health risks as obesity.

Definition

The term "metabolically obese normal weight" (MONW) refers to people with normal weight and body mass index (BMI), who display some metabolic characteristics which increase the risk of developing metabolic syndrome in the same way as obesity. People with MONW have excess visceral fat, and are predisposed to hyperinsulinemia, insulin-resistance and thus predisposition to type 2 diabetes, hypertriglyceridemia, hypertension and premature coronary heart disease or cardiovascular disease. The BMI does not capture information about percentage body fat (PBF), which is a better predictor of risk due to obesity. Some studies have suggested that the main factor which explains the metabolic abnormalities in MONW individuals is fat distribution. On the basis of these studies, a scoring method has been proposed to identify MONW individuals, based on the presence of associated diseases or biochemical abnormalities related to insulin resistance.

Prevalence

In 2008, the first prevalence of US adults above 20 years was published, based on the National Health and Nutrition Examination Surveys from 1999-2004, finding that 24% of normal-weight adults were metabolically abnormal; on the other hand 51% of overweight adults and 32% of obese adults were metabolically healthy. An analysis from an earlier NHANES from 1988 to 1994 found people with NWO had a four-fold higher frequency of metabolic syndrome compared with the low body fat group.

Treatment

As of 2018, optimal treatment is unknown. A 1998 study suggested that energy restriction and weight loss, for example a 4- to 12-week period of diet and exercise was beneficial. A small study of 11 Asians with MONW published June 2018 found that moderate weight loss through dieting reduced their cardiometabolic risk per improved body composition, lipid profile, and insulin sensitivity.