So how many of us are normal in a BMI sort of way? According to recent US data, roughly one-third of adults have bypassed normal into overweight (BMI 25-30) and an additional one- third weigh in at obese (BMI 30 and above). Epidemiologists warn that the obesity epidemic is increasing the incidence of chronic disease.
Statisticians from the CDC conducted a meta-analysis (combining data from many studies) of nearly 3 million subjects from 97 separate studies that looked at all-cause mortality over time as related to BMI(1). Relative to normal BMI, the researchers compared the risk of dying in those overweight (BMI 25 to 30) and obese (BMI 30 and above). The researchers used hazard ratios (HR) to express their findings, a measure of how often a particular event happens in one group compared to how often it happens in another group during the course of a study. They found that the overweight and the grade 1 obese were slightly less likely to die than those in the normal BMI range (HR=.95). On the other hand, those with BMIs at or above 35 had a calculated HR of 1.29, nearly a third again more likely to check out early than those weighing less.