The more overweight you are, the more likely you are to die.
Put another way: Being overweight or obese is associated with a higher risk of dying prematurely than being a healthier weight — and the risk increases with additional pounds, according to a new international study led by researchers at the Harvard T.H. Chan School of Public Health and the University of Cambridge in the U.K. Researchers joined forces in 2013 to establish the Global BMI (Body Mass Index) Mortality Collaboration, which included more than 500 investigators from over 300 global institutions.
Looking at specific causes of death, the study found that, for each five-unit increase in BMI (from, say, 30 to 35) — body mass index is measured by a formula that divides your body weight your height — the corresponding increases in risk were 49% for cardiovascular mortality, 38% for respiratory disease mortality and 19% for cancer mortality. That means these people are 49%, 38% and 19% more likely to die earlier than a person who has a healthy body weight.
BMI calculates weight, muscle, fat and bone in relation to height and gender. A BMI of 25 to 29.9 is considered overweight and those with a BMI of 30 or more are considered obese; morbidly obese people have a BMI of 44.9 or more. Adult obesity exceeds 30% of the population in 20 U.S. states and surpassed 35% in three states — Arkansas (35.9%), West Virginia (35.7%) and Mississippi (35.5%). Also, 22 states have rates above 30%, 45 states are above 25%, and every state is above 20%.
What’s more, the hazards of excess body weight were greater in younger than in older people and in men than in women, the researchers found. They crunched data from more than 10.6 million participants in 32 countries from 239 studies, conducted between 1970 and 2015. A combined 1.6 million deaths were recorded, in which participants were followed for an average of 14 years. Current or former smokers or those who had chronic diseases were excluded, as were those who died in the first five years.
There have been conflicting studies about obesity and mortality. In fact, a higher BMI may be associated with a lower mortality and a better outcome in several chronic diseases and health circumstances, according to a 2013 study published in Diabetes Care, the official journal of the American Diabetes Association. (The study also noted that BMI is “crude and flawed” and doesn’t take into account fat mass, nutrition, cardiorespiratory fitness, body fat distribution, or other factors affecting mortality.)
But this “obesity paradox” is flawed, the latest study argues. A low body weight could be the result of underlying illness rather than the cause. What’s more, smokers tend to weigh less than nonsmokers but have much higher mortality rates.
Still, as the mortality collaboration shows, there are significant health risks associated with being overweight. “Physicians need to counsel patients about the dangers of excess body weight which include a higher risk of Type 2 diabetes, cardiovascular disease, cancer and premature death,” says Shilpa Bhupathiraju, research scientist at the department of nutrition at the Harvard Chan School of Public Health.