Calorie restriction: can it help you live longer?

Calorie restriction—where you deliberately reduce your energy intake for months or years at a time—has been linked in some studies to impressive health benefits, including a longer life. There are a lot of ways to calorie-restrict, but the general idea is to consistently reduce your daily calories. Intermittent fasting, where eating is avoided at certain times or on certain days, is another approach that’s gotten a lot of attention.

But can eating less as a way of life extend your lifespan? Is it real, and if so, is it really worth it? Here’s what the science says.

Calorie-restriction research looks promising

Scientists have been studying calorie restriction for decades, finding that it can extend the healthy lifespan of lab rats as well as simpler creatures like yeast, fruit flies, and worms. Not all studies agree, however. Some research has found that it shortens the lifespan of mice in some cases. But research in humans has long linked certain patterns of restricted eating to better health, including better handling of blood sugar, loss of excess weight, better blood cholesterol, lower blood pressure, and lower levels of inflammation. All these changes can reduce wear and tear on your body as you age.

A small 2019 study published in Cell Metabolism found that healthy, middle-aged humans who fasted every other day for six months saw improvement in several health indicators, including waistline fat, blood pressure, and heart rate.

A 2017 study in Nature Communications described what happened to rhesus monkeys who started a 30-percent calorie restricted diet once they were fully grown, while fellow monkeys ate more or less as much as they liked. Rhesus monkeys eat, sleep, and age in much the same way humans do. The low-cal monkeys lived much longer, with one still alive at 43, a record among rhesus monkeys, and the human equivalent of 130 years old. The monkeys also had a lower incidence of age-related diseases, like diabetes and heart disease.

So should I just go hungry all the time if I want to live longer?

It’s not that easy. There’s not enough evidence yet that calorie restriction or intermittent fasting are safe or effective over the long term. The 2019 study’s authors cautioned that it wasn’t clear how people would have fared if the study had gone on longer than 6 months.

Also, it’s not clear how feasible such eating patterns are. Counting calories is burdensome, and as anyone who has tried to lose weight knows, eating less than you’d like isn’t easy. One calorie-restriction study of human volunteers had more than a 25 percent dropout rate.

Whether people can commit to eating far less, day after day, all the while avoiding becoming malnourished, is doubtful. And intermittent fasting isn’t necessarily easier. If you’re thinking of trying intermittent fasting, first discuss it with an HCP. You may be at higher risk for ill effects from fasting if:

• You have diabetes
• You’ve previously had an eating disorder, such as anorexia or bulimia
• You are pregnant or breastfeeding

People in these situations should not try intermittent fasting except under close medical supervision.

Finally, these eating patterns themselves could turn out to be beside the point. Some scientists say that a major point of this research is to help unravel how aging works so that a drug could potentially be developed to extend healthy lifespan.