“I think Kathy Flegal just doesn’t get it that people often lose weight before they die,” Willett told me.
In 2016, Willett and dozens of other researchers from around the world published a paper in The Lancet analyzing 239 studies and millions of study subjects. Their takeaway was clear: Above the normal weight range, the fatter you are, the higher your risk of premature death. “On average, overweight people lose about one year of life expectancy, and moderately obese people lose about three years of life expectancy,” the paper’s lead author, Emanuele Di Angelantonio, told The Guardian.
Flegal takes issue with how Willett and his colleagues selected the studies for their review. “It seems like they took studies they already knew about and that gave the answers that they preferred,” said Flegal, who is now a consulting professor at Stanford.
Besides, other studies have since implied there’s a health benefit to heaviness. Last year researchers in Copenhagen looked at three cohorts of Danes during the 1970s, ’90s, and between 2003 and 2013. In the 1970s, the BMI that was associated with the lowest risk of death was 23.7—so-called normal weight. Surprisingly, by the 2000s, the “healthiest” BMI had shifted up to 27, or technically overweight.
Børge G. Nordestgaard, a clinical professor at the University of Copenhagen and an author of that study, speculated that this could be because over time, doctors have gotten better at treating some of the side effects of excess weight, like high blood pressure and high triglycerides.
Or, “it could just be that as the population has become more overweight and obese, the people who are in the middle of the BMI distribution, these are the most ‘normal’ people, they are the ones who do all the most normal things,” Nordestgaard said. “They are the ones who survive the best.”
What’s more, in 2014, New Orleans cardiologist Carl Lavie published the book The Obesity Paradox: When Thinner Means Sicker and Heavier Means Healthier, based in part on his research showing that overweight and mildly obese patients with cardiovascular disease have a better prognosis than their leaner counterparts.
But when reporters found that Lavie had received money from the Coca-Cola Company for speaking and consulting on obesity, it fueled speculation that junk-food companies are promoting the supposed benefits of obesity in order to evade blame for causing it. (In an email, Lavie said Coca-Cola only funded a few of his lectures, of which he gives more than 100 a year.)
Andrew Stokes, the demographer at Boston University, says some of most vocal supporters of the “obesity paradox” are activists and people with vested interests. He’s found that the paradox disappears when “normal weight” is defined as only those people who have remained thin over time, as opposed to those who entered the normal-weight category after losing weight due to an illness. In a paper published this April, Stokes, Willett, and others found being overweight was associated with mortality—but only if you looked at a person’s maximum weight over the past 16 years. According to their findings, it’s having ever been overweight that’s risky.