So what’s the culprit? Sugar plays a major role, along with the increasing consumption of vegetable oils that can result in fat accumulation around the liver—even among thin people, according to panelists discussing healthy eating at the AIC 2016 on April 6.

Perhaps surprisingly, research in the US shows that many thin people suffer from a condition called “metabolic syndrome,” which is similar to prediabetes and can lead to heart disease. In fact, about half the population has this condition.  

“There’s no question that people who are obese have a higher risk,” said Robert Lustig, Professor of Pediatrics, Division of Endocrinology, at the University of California. “But there are more thin sick people than fat sick people.”

The good news is that the problem can be mitigated if it’s diagnosed by middle age. Replacing sugar with starch – say, eating bagels instead of donuts – and avoiding processed foods with added sugar can make a big difference.  Unfortunately, natural sweeteners like honey or agave nectar don’t help. They do the same amount of damage.

“Every diet on the planet that works is a low sugar, high fiber diet,” Lustig said.

A range of other factors also influence how long a person will live, said Peter Attia, founder and former President of the Nutrition Science Initiative.

Genetics play a big role, with 75 percent of people likely to live into their 70s and 80s. About 10 percent are predisposed to live past 90 and about 15 percent are likely to die in their 50s.

“You can stretch it, but you have to be willing to do it early,” Attia said. “If you are in your 40s or 50s and you have metabolic syndrome, there is an opportunity to intervene.

Besides a healthy diet, Attia cited exercise, sleep quality, stress management and having a sense of purpose among factors that add to longevity.