But now pharmaceutical companies are rolling out new prescription drugs that really do help people lose and keep off significant amounts of body fat. A body mass index measures the ratio of a person's height to his weight to roughly estimate his amount of body fat. Various epidemiological studies find that obesity correlates with shorter life expectancy and worse overall health. The WOF study estimates that the economic impact of overweight and obesity will reach $4.32 trillion annually by 2035, about 3 percent of global GDP. The Economist declared, "New drugs could spell an end to the world's obesity epidemic."