Body mass index (BMI) is a strong predictor of death, finds an analysis of 57 studies involving nearly 900,000 adults that appeared in the March 28 Lancet. Overall death rates were lowest at BMIs of 22.5 to 25 (a BMI of 25 is considered overweight; greater than 30 is obese). Each 5-unit increase in BMI above this range raised the death rate by 30%. Increased death rates at BMIs above 25 are largely because of vascular disease, whereas smoking-related illnesses are the main cause of the rise in death rates at BMIs below 22.5. Current BMI cutoffs, however, may not fit all ethnic groups. Using dual-energy X-ray absorptiometry to measure body fat, researchers reported in the April 16 British Journal of Nutrition that blacks have 2% to 5% less fat than whites, whereas Asians and Hispanics have significantly more fat. The authors suggest that BMI cutoffs should be higher in blacks but lower in Asians and Hispanics. According to a study of 8,550 children in the April Archives of Pediatrics and Adolescent Medicine, obesity is evident in U.S. children as young as four years of age. Based on BMI, 31% of American Indian or Native Alaskan, 22% of Hispanic, 21% of black, 16% of white, and 13% of Asian children are obese.