- Researchers have new evidence that reducing calorie consumption may help people live longer.
- A study of Americans who reduced how much they ate by 15% for two years found that they used energy more efficiently, kickstarted their metabolism, and turned off some damaging signs of ageing.
- The find goes along with previous research on calorie consumption from around the world: people who are forced to eat less for years at a time tend to live longer.
Eat less, live more.
That seems to be the conclusion of a growing pile of research conducted on both people and animals around the world.
Perhaps nowhere is this more true than in Okinawa, Japan. Before the 1960s, schoolkids in the poorer, war-torn prefecture routinely consumed only 62% of the calories that their Japanese counterparts in other areas of the country were eating. When the Okinawa kids grew up, they turned out much healthier – they have often been touted as some of the very healthiest, longest-living people in the world.
Now researchers are finding evidence that the same kind of reduced-calorie diet could be good for modern Americans, too. A small study of 34 people, who cut down on what they ate by 15% for two full years, found that compared to people who kept eating their regular portions, those dieters slowed down critical ageing processes inside the body.
The dieters didn’t follow any specific rules during the study. The important thing was that they cut down on what they were putting on their plates and in their mouths by about one sixth. Most of these study participants weren’t old; their average age was around 40.
But by restricting their diets for two years, not only did those people lose 5% or more of their body weight (much of it fat), their nighttime core body temperature dropped and their fasting insulin levels lowered – two key biomarkers of ageing.
Why eating less can help you live longer
If you think of your body like a well-oiled machine, the idea of restricting how many calories you’re putting inside makes a lot of sense. By eating fewer calories, you’re putting less stress on your digestive system. Like a car, if you drive it around less frequently, you’re going to see less wear and tear on the tires.
Dan Buettner, who for years has studied what he calls the “Blue Zones” of the world – the places where people tend to live the longest and the healthiest – says when we eat fewer calories, our bodies oxidize less, and have to deal with fewer free radical byproducts.
Having too many toxic free radicals floating around can lead to cancer, tax our arteries, shrink our brains, and less directly, cause more wrinkles.
Plus, when we consume fewer calories, our cells have less work to do, converting food we eat into fuel. Reducing calorie consumption may help give our bodies a much-needed break.
“Put simply, it causes us to rust less from within,” Buettner said.
Attempting a reduced-calorie diet doesn’t necessarily mean consuming less food. Many countries around the world nosh down lots of nutrients while taking in fewer calories than average Americans. These nutrient-dense foods usually include a heaping dose of fresh vegetables. In Japan, for example, people tend to eat lots of fibre-filled tubers and starches, like sweet potatoes.
Still, going on a reduced-calorie diet is not easy to do from a biological standpoint. For much of human history, it was nearly impossible to get too many calories. When there was an abundance of food, it was in our best interest to gobble up as many calorie-dense treats as possible. That’s not the case anymore.
Eating less isn’t always a good thing, though
The science is still evolving on whether reduced-calorie diets are good for everyone at every age. Some reduced-calorie diet studies (in monkeys) have suggested that monkeys who are fed less don’t live any longer than others. Even in humans, ageing is a complex phenomenon that’s not completely understood.
Nutritionists like Lareina Lee, Chief Clinical Dietitian at Upper East Side Nursing and Rehabilitation Center in New York, say there’s not yet enough evidence that calorie restriction leads to longer life spans in humans, either.
She says the idea of restricting calories without paying attention to the kinds of foods your putting into your body misses the point of healthy eating.
“Instead of restricting calories (unless you are overweight or obese), it is more important to focus more on where your calories are actually coming from, and to remember to eat in moderation and not in excess,” Lee said in a statement.
Claudia Kawas, who’s been studying over 1,600 volunteers who make it beyond age 90 for the past 15 years, recently found that many who become nonagenarians drink alcohol regularly and have a little paunch, too. She thinks being skinny and temperate when you’re really old probably isn’t the best way to stay alive.
After all, when you’re old, a little extra fat could help you live through a bad bout of illness. Plus, since older people’s systems don’t absorb nutrients as efficiently, they might need to eat a little more than younger people to stay healthy.
Buettner thinks it’s possible that the very old can be fine with a little extra fat on their bellies, too. But he cautions that many people who elected to be in Kawas’ study may have won the genetic lottery, and are outliving others because they have got stellar genes.
“There are some people who are just stronger,” he said. “They’re able to elude chronic diseases better than other people.”
Scientists aren’t yet suggesting that everyone try cutting their diet down by 15%. But they are starting to study whether restricting calorie intake more intermittently (for example, on a few chosen days each month) could also slow down the ageing process. That might be more manageable, and it could possibly work just as well at keeping us young as fasting all the time.