A new study holds out hope that cutting our calories even by a little bit can help keep us healthier and extend our lives.
The National Institutes of Health study published in the Journal of Gerontology: Medical Sciences, reports that restriction of calories modified the risk for age-related diseases and factors related to a longer life span. That includes an impact on blood pressure, cholesterol and insulin resistance.
Researchers say the restriction of calories has been shown in numerous animal studies to increase longevity and reduce age-related diseases. Those studies, however, show that the best impacts of that is when the calorie restriction starts in youth or early middle age.
The most recent study on humans was done over two years and involved 218 people who were no older than 50, researchers say. They included people of normal weight and who were moderately overweight, plus a control group on their regular diet.
The study results showed that calorie reduction decreased average blood pressure by 4 percent and total cholesterol by 6 percent. Levels of HDL or good cholesterol increased. Researchers say the calorie reduction caused a 47 percent reduction in the levels of C-reactive protein, an inflammatory factor linked to cardiovascular disease. It also reduced insulin resistance, which reduces risk of diabetes. Researchers say a thyroid hormone decreased by more than 20 percent, and some studies have shown that's associated with lower life span.
Researchers say that reducing calories, meanwhile, doesn't hurt a person's mood. In a few cases, people developed transient anemia and a decrease in bone density. We've already seen studies that show a bad diet can cause bad mental health.
"The results are quite intriguing," says Evan Hadley, director of NIA's Division of Geriatrics and Clinical Gerontology and an author of the study. "They show that this degree of sustained calorie restriction can influence disease risk factors and possible predictors of longevity in healthy, non-obese people. Since this group already had low risk factor levels at the start of the study, it's important to find out whether these further reductions would yield additional long-term benefits. It also would be useful to discover if calorie restriction over longer periods has additional effects on predictors of health in old age, and compare its effects with exercise-induced weight loss."
Researchers say the participants had a target of a 15.5 percent weight loss in year one of the study and weight stability in the second year. The focus was for people to reduce calories by 25 percent of what they normally consume at the start of the study.
What happened, though, was those participants instead reduced their calorie intake by 12 percent. That caused a 10 percent weight loss that was maintained over the two years.
Hadley said that level of calorie reduction is certainly doable for many people to undertake, but the research isn't at the point of making recommendations to the public, pending further study.
"For many years, it's been shown that lowering caloric intake in lab animals if started early will extend lifespan and delay the onside of age-related diseases," Hadley says.
When it comes to people, Hadley says, if people start this much later in life it may not do "any good at all." He said a pilot study done several years ago that looked at those people between 50 and 60, however, showed similar benefits for reducing calories.
Hadley says the reduction in calories that people did wasn't a starvation diet and easily doable for those participating. For most, that is reducing calories from an average of 2,500 a day to about 2,200.
"I'm not saying it's easy, but it's not an outrageous amount," Hadley says.
Hadley says it will be interesting to look at the calorie restriction and exercise and see which factors makes more of a difference. There are studies that look at the relationship between exercise and cancer.