Can dramatically cutting calories help people live longer?
Why we age, and how to slow it down has been a subject of study for centuries. Life expectancy for men in 1900 was approximately 47 years and women was 49. By the year 2000 the average man could expect to live 75 years and woman 80.
Over those 100 years, our lives have been extended by improvements in living conditions like better sanitation, improved heating and cooling as well as safer working conditions. With advanced farming techniques we have significantly increased availability of food. Meanwhile healthcare has given us dramatic drug and medical breakthroughs.
Most of the successes have been from changing external things that affect us. At some point, we begin to bump up against the limitations of human biology. Geneticists believe that our bodies reach a point, where they can't repair damaged cells fast enough. Eventually the cumulative damage becomes too great and we die. Right now that upper threshold of age is believed to be somewhere between 115 and 125 years.
Instead of focusing on the external, a small group of scientists decided to look inward. They've been trying to figure out if there are things we could do with our bodies, that might extend life. There are two areas researchers focus on.
The first area is exercise. The importance of regular activity has been accepted for decades. Researchers know that adding just three hours of weight-training a week into your schedule can help people live an additional 5-12 years.
Diet is the other area. Getting enough food was a problem in the 1900s, but today it's making sure we don't eat too much. Children born today may actually live shorter lives than their parents, simply from the negative health affects of being overweight.
But researchers have taken it beyond dieting, to see what happens when people UNDER eat. It's known as caloric restriction (CR). Scientists found that they could extend the life of lab animals by reducing the amount of calories they take in by 10 to 40 percent.
Caloric restriction is not the same as fasting. When a person is fasting, they do not eat at all during certain times of the day, week or month. With caloric restriction you eat, but the number of calories you take in are below what is typical or habitual. One of the tricks is not cutting calories so much, that you go below the minimum amount of vitamins or minerals your body needs.
Caloric restriction has been tested on worms, crabs, snails, fruit flies, rodents and monkeys. In general, caloric restriction delayed the onset of age related disorders. In several studies it also extended how long the subjects lived. A rhesus monkey was put on a caloric restriction diet when he was 16. He ended up setting a longevity record for his species, living to the ripe old age of 43. That's the same as a human being living 130 years.
So far there have been two National Institute on Aging (NIA) sponsored studies done on rhesus monkeys. In both cases, caloric restriction was identified as the reason for a reduction in age-related conditions. The monkeys had fewer instances of cancer, diabetes and heart disease. Unfortunately, the studies results have been mixed. One showed that the monkeys lives were extended, the other did not.
We need human studies, and that's just what the NIA did. A study called Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) was conducted. 218 normal-weight or moderately overweight adults were divided into two groups. One group followed their usual diet. The other was supposed to reduce their average daily calories by 25% over the next two years.
Turns out that drastic calorie reduction wasn't achieved. On average, the experimental group only cut their daily caloric intake by 12%. However, even with that lower number, they still achieved a 10% loss in body weight over those two years.
A follow-up that was conducted two years after the study ended, showed participants sustained much of the weight loss. The experimental group also had lower blood pressure and lower cholesterol, reducing their risk for age-related diseases including diabetes, heart disease and stroke. Because of the short length of the study, it's unknown if the subjects will actually live longer or not.
The biggest problem with caloric restriction is that it's uncomfortable. People who practice it have periods of hunger. It requires a level of self-restraint in a society where food temptations are everywhere. It's certainly something that should continue to be investigated, but it doesn't offer a solution to deal with our current obesity crisis.
With the long term success of any diet plan hovering around 5%, people would be better served if food companies found ways to reformulate their products. Promote tasty vegetable dishes that are more filling but less calorie dense. Ask stores to remove junk food displays at register checkouts. To achieve real breakthroughs in diet related longevity, we need to make healthy food choices just as appealing and convenient as burgers and fries are today.
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