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Heart disease is the leading cause of disability and death worldwide. About 2,200 people in the US die every day from cardiovascular problems or every 40 seconds.
In that sense, if you knew you could keep your heart healthy by eating a little less each day – about six standard-sized Oreos calories – would you?
Researchers have found evidence that only a modest reduction in our daily calorie intake could have protective effects on our heart, according to a paper published in The Lancet Diabetes & Endocrinology this week.
The article was based on data from the study "Comprehensive Assessment of the Long-Term Effects of Reducing Energy Consumption" (CALERIE). This groundbreaking project, supported by the National Institutes of Health, was one of the most thorough efforts to measure the long-term effects of calorie reduction in humans. Researchers have published numerous analyzes based on data from the biennial study examining various factors related to life expectancy and longevity. This may prevent the age-related decline.
The experiment began with 218 participants, all of whom were of normal weight or slightly overweight and between 21 and 50 years old. The researchers began 143 dieters who reduced their calorie intake by 25%. 75 others were assigned to a normal diet. In the end, 188 participants completed the study – 117 with calorie restriction and 71 without.
In the first four weeks of the study, people in the calorie reduction group were fed internally at one of three clinical centers. During this time, they were instructed on how to reduce their calorie intake and gradually fell into one of six nutritional plans that matched their own preferences.
For the first six months, most people behaved quite well with their diets. On average, they reduce calories by about 20%. But over two years, they did not fare so well: Overall, they reduced their calorie intake by an average of 12% – or by 300 fewer calories per person per day.
Nevertheless, this relatively modest calorie reduction had a significant impact on those who ate less: they lost an average of 16.5 pounds and saw improvements, including lower cholesterol and blood pressure, for all six major factors at risk for the heart connected were health. They also saw improved insulin resistance and metabolic rate.
"We expected an improvement in cardiometabolic factors due to weight loss," said William Kraus, lead author of the study and a respected professor of cardiovascular genomics at Duke University. "But … we did not expect the extent of the observed improvement to change."
Although the weight loss was relatively impressive, he was not responsible for much of the cardiac benefits. After further analysis, the researchers found that weight loss was no more than 25% of improved heart health measurements. The researchers say that their findings suggest that calorie reduction can have health benefits that go beyond those normally associated with weight loss to ward off the negative effects of aging.
However, the study also shows a significant problem with using calorie restrictions to improve human health: it is very difficult to care for even motivated people. Of the 143 participants who originally started on the restricted diet, 26 retired before the end of the two years. (Small samples were a limitation of the study.) Many others were picked out of the initial study pool because they were worried about their physical or mental health.
"One can not expect that elderly or infirm people will follow this strict diet regimen," says Sinclair, who was not involved in the study. "We need alternatives, be it intermittent fasting or drugs that mimic calorie restriction." He is working to understand how calorie reduction works on a molecular level so that he and others can develop drugs that bring the same benefit without pain and difficulty.
The goal of any research on calorie restriction, he says, is the reduction – and possibly elimination – of age-related diseases.
"Aging is not considered a disease – it's just too common, hopefully we will not accept it in the near future," he says. "It provides calorie reduction: It shortens the disease phase, and people will one day hopefully live healthily until the '90s, passing faster and more painfully than they do now."
Susie Neilson is an intern at the Science Desk of NPR. Follow her on Twitter: @susieneilson .