Followers of an Isagenix system complete with Shake Days and Cleanse Days can look forward to possibilities of lifelong health—because of reduced bodyweight, muscle maintenance, and optimal nutrition—and perhaps even a longer life from consistently eating fewer calories.
Since the 1930s when Cornell University researcher Clive McCay reported that a reduction in calories (without undernutrition) extended mammalian lifespan, hundreds of subsequent studies conducted found it could extend lifespan and delay the onset of age-related outcomes in a variety of species.
Research over the past 80 years brings hope that the same results could transfer to humans, although, calorie restriction (CR) studies in humans are lacking. However, there are already exciting results suggesting that CR very well may protect health and extend life.
One group of humans that have provided evidence from a “natural experiment” in long-term CR is the older generation of Okinawans from Japan. Because of poverty when they were younger, these Okinawans were so deprived of calories that it stunted their growth, but, even so, their quality of diet was adequate enough to keep them free of nutritional deficiencies and poor health that afflict most of the third world.
To this day, there are more people who have lived over 100 years of age in Okinawa than in any other part of the world—leading researchers to believe this may be evidence that CR may provide protection from the effects of aging in humans.
There are relatively few actual studies on long-term CR in humans. A famous one that was accidental was as part of an entirely different experiment, Biosphere 2. Eight volunteers were sealed inside an enclosed three-acre space meant to be an “ecological mini-world”. They ran into problems when their food supply unexpectedly dwindled to meager portions.
Coincidentally, the crew’s physician, Roy Walford, M.D., was one of the pioneers in CR, so he convinced his fellow biospherians to embark on their own CR experiment. Their results showed that CR decreased BMI, blood pressure, fasting blood glucose, insulin, and cholesterol.
Calorie Restriction Society
Another source for information on humans restricting their food intake is from the Calorie Restriction Society (CRS) whose members adhere to a CR regimen because of evidence from animal studies.
Data collected show the CRS members exhibited similar results as the subjects in Biosphere 2. Of particular notice was their low blood pressure and reduced incidence of chronic oxidative stress compared to similarly aged individuals.
The growing interest in the effects of CR in humans has led to a multi-collaborative research program, CALERIE (Comprehensive Assessment of Long-Term Effects of Reducing Calorie Intake). This program is a joint effort of the National Institute on Aging along with several other research centers (Tufts University, Pennington Biomedical Research Center, Washington University, and Duke University) whose goal is to research the effects of long-term CR in humans.
Phase I of CALERIE consisted of three pilot studies that examined healthy, overweight men and/or women (BMI 25-29.9 kg/m) and restricted their calories by varying degrees for six or 12 months.
Results showed that CR led to decreases in body weight, fat mass, core body temperature, visceral and subcutaneous fat mass. The study also showed decreased fasting glucose and improved insulin sensitivity.
Future studies will target younger individuals with lower BMI (not overweight or obese).
Although the research on CR in humans is still in its infancy, what has been found so far suggests similar life-extending benefits as previously demonstrated in animal studies.
Holloszy JO, Fontana L. Caloric restriction in humans. Exp Gerontol 2007;42:709-12. doi: 10.1016/j.exger.2007.03.009
Chan YC, et al. Dietary, anthropometric, hematological and biochemical assessment of the nutritional status of centenarians and elderly people in Okinawa, Japan. J Am Coll Nutr 1997;16:229–235.
Heilbronn LK, et al. Effect of 6-month calorie restriction on biomarkers of longevity, metabolic adaptation, and oxidative stress in overweight individuals: a randomized controlled trial. JAMA 2006;295:1539–1548.