Cutting Calories by 15% can keep you Young - New Study Says
Perhaps there is no need for a fountain of youth after all...
We have known that in animal studies (mainly in mice) that calorie restriction leads to extended life with less chronic diseases. Now there is a study that shows this to be true for people as well.
New research just published in the Journal of Cell Metabolism suggests that reducing calories by 15% for two years can slow the metabolic process that leads to aging and protect against age-related diseases.
After just one year on a reduced-calorie diet, study participants saw their metabolic rates drop significantly. The lowered rate continued into the second year and led to an overall decrease in oxidative stress, a process that has been tied to diabetes, cancer, Alzheimer's disease and other age-related conditions.
"Reducing calorie intake provides health benefits to all people regardless of their current health status," says Leanne M. Redman, lead author of the study and an associate professor at Pennington Biomedical Research Center at Louisiana State University.
The new CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy) study was designed by Redman, her colleagues and the National Institute on Aging to answer a simple question: Would the same be true in humans?
Aging biomarkers
During the first phase, teams of researchers ran small-scale pilot experiments to answer a variety of questions including, what kind of calorie restriction could study participants actually stick to? To this end, some of the pilot studies tested a diet-only calorie reduction, others tested exercise only, and still others tested half-diet, half-exercise. Another question posed by the researchers: What level of calorie restrictions would have an impact on biomarkers of aging?
Aging biomarkers are simple biological measurements that differentiate longer-lived people - those who celebrate birthdays into their 90s and 100s - from people who live the average life expectancy. We know that longer-lived individuals are able to sustain lower blood sugar levels and lower levels of insulin and have lower core body temperature levels in comparison to people who don't live as long as them.
After the pilot studies, the National Institute on Aging committed to funding larger phase two CALERIE studies at three universities: Pennington in Baton Rouge, Washington University in St. Louis and Tufts University in Boston.
At Pennington, the focus was on reducing calories by 25% through diet alone. Women between 25 and 45 and men between 25 and 50 were recruited; about half were normal weight and the other half overweight but not obese. Throughout the study, participants ate what they liked, yet they also took vitamins and supplements to ensure that their diets were "nutritionally adequate". Each participant was also given a scale. Instead of calculating daily calories and slashing them by 25%, weight loss was used to estimate the total reduction in calories for each participant over time.
However, the participants did not hit the 25% reduction as anticipated, but they did achieve a 15% calorie restriction, over the two years. Regardless, the results from this lesser calorie restriction amount were fairly remarkable.
For example, participants lost an average of about 20 pounds each by the end of the first year and maintained that loss during the second year. The calorie-restrictive diet also caused a reduction in sleeping metabolic rate by about 10% and this remained true after one year, when weight loss peaked, and after two years, when weight remained constant. A slower metabolism means the body has become more efficient in using fuel - whether from food or oxygen - to derive energy.
This is important because every time we generate energy in the body, we also generate byproducts. These byproducts of normal metabolism, also called oxygen radicals, accumulate in the body and over time cause damage to cells and organs leading to diseases such as diabetes, cancer, dementia and a shortened lifespan.
A Breakthrough
The "breakthrough" with this study is that it is the first randomized controlled trial of calorie restriction in humans. Randomized, controlled trials (RTCs), in which participants are divided by chance into groups to compare interventions, are considered more valuable to scientists than other types of experiments. This study is the first RTC, since all previous studies of calorie restriction in humans have been on a voluntary basis.
We have known since the 1930s that calorie restriction reduces the rate of aging and extends lifespan in rodents. Since then, studies in different animals mostly show the same general pattern. For this reason, this study is important as it showed in humans two key changes previously observed in calorie-restricted rodents: lowered metabolic rate and reduced production of radical oxygen species.
Exactly how calorie restriction prevents aging remains a question, but the research so far supports two theories of longer life: the "rate of living" (lower metabolism) and reduced oxidative damage.
A Few Ways to Reduce your Calories and Stay Young
Eating lots of vegetables, fruit and follow an anti-inflammatory eating pattern.
See the previous article about losing weight without dieting.
Engaging in a regular exercise program - see the recent related article on exercise and aging.