Calorie restriction may not extend monkeys’ lives after all, new study suggests

By Deborah Kotz, Globe Staff

Here’s some upsetting news for those following calorie-restricted diets in the hope that they’ll live longer: it doesn’t appear to extend lifespan, at least in monkeys, according to a National Institute of Aging study published Wednesday in the journal Nature. That’s comforting for the rest of us who may not want the frequent hunger pangs, chills, and gaunt-looking body common to those who have reduced their calorie intake by up to 30 percent for years or decades.

The latest study certainly doesn’t provide a firm answer to the question of whether calorie restriction helps us live longer. In fact, it contradicts a 2009 study from the Wisconsin National Primate Research Center, which found that monkeys put on a calorie-restricted diet lived longer and healthier lives.

But that earlier study may have had some shortcomings: The monkeys were all fed relatively unhealthy diets, with nearly one-third of their calories from sugar, so the calorie-restricted monkeys may have been healthier and lived longer simply because they ate less sugar.

In contrast, the monkeys in the new trial ate only 4 percent of their calories from sugar, regardless of whether they were on a calorie-restricted or normal diet used for comparison. All of the monkeys were also fed fish oil and other nutrients that were lacking in the Wisconsin study, and, as a group, they wound up weighing less, on average, compared with the Wisconsin monkeys who had more body fat.

Genetics may have also played a role because monkeys in the two different studies didn’t come from the same countries.

In the latest study, some of the monkeys on the calorie-restricted diets enjoyed some health benefits over their counterparts. Male monkeys, though not females, who started eating fewer calories in old age had lower levels of cholesterol and blood sugar, and both genders had lower levels of triglycerides which may have protected them against heart disease.

Those monkeys who were put on the lower calorie diet when they were young didn’t have these benefits, though they didn’t had lower rates of cancer. This, however, didn’t help them live any longer.

“These results suggest the complexity of how calorie restriction may work in the body,” Aging Institute director Dr. Richard J. Hodes said in a statement. “Calorie restriction’s effects likely depend on a variety of factors, including environment, nutritional components and genetics.”

Deborah Kotz can be reached at dkotz@globe.com. Follow her on Twitter @debkotz2.