A proposed revision to the body mass index (BMI) system could lead to millions of Britons being classified as obese. Under the proposed changes, adults over 40 with a BMI of 27 or higher would be considered obese, significantly expanding the current definition. The authors argue that the current BMI threshold for obesity may not be appropriate for middle-aged and older adults, as bodies tend to experience increased fat accumulation around the waist after age 40. Critics point out that the study did not account for factors such as diet, exercise levels, and sleep patterns, which can influence obesity risk. The BMI system, developed in the 1830s, has faced criticism for its outdated calculation method, which does not distinguish between fat and muscle mass.