A well-known Chinese saying goes, “When eating, stop when you are seven tenths full”, while the great 7th century physician and all-round wise guy Sun Simiao said, “This is the special method of lengthening the years and eating for old age.”
These radical ideas have been confirmed over the past few decades by extensive research into calorie restriction (CR). Small creatures such as mice, rats, fruit flies, worms and so on (with generally short and therefore more easily studied lifespans) all live longer and suffer fewer diseases of old age when their diet is restricted in total calories yet nutritionally adequate.
The big question is whether the same applies to humans. There is some epidemiological evidence to suggest it is so (the modest lifelong calorie consumption of extremely long-lived Okinawans), and some actual research – improved biological markers in humans on long-term CR diets. For example when 200 people with healthy weight cut their calorie intake by 11% over two years, their inflammation and risk factors for heart and metabolic disease were reduced1. The length of human lifespan, however, makes other research difficult or impossible to conduct.
The next best thing is monkeys – specifically rhesus macaques, who age in very similar ways to us, yet only live one third as long. Because of this, two studies have been conducted into CR and macaques but frustratingly, they came up with different results causing much puzzlement.
Study One (University of Wisconsin) found that reducing calories by 30% over 20 years reduced rates of heart disease, diabetes, cancer and death2.
Study Two (National Institutes on Aging) found that though the monkeys’ health improved, they didn’t live any longer3.
So both agreed on the health advantages but not on the longevity issue.
Now a more detailed comparison of the studies has thrown some light on the issue. In study one, the monkeys were fed a highly artificial diet (containing nearly 45% sugar!). That meant that the monkeys used in the control group were fatter and more unfit than the study monkeys who ate the same ‘junk food’ diet, but less of it.
In study two, both groups (study and controls) were fed a more natural food diet containing only 7% sugar.
So the tentative conclusion (as more studies are conducted the picture will hopefully become clearer) is:
- Eating a natural diet and restricting calories results in significantly healthier aging but no apparent improvement in longevity.
- Eating a junk food diet and restricting calories improves health in old age as well as longevity.
- This is somewhat backed up by a hilarious study carried out by Mark Haub, a professor of human nutrition, in 2010. For 10 weeks he ate only Twinkies (a ‘golden sponge cake with creamy filling’), Hostess and Little Debbie snacks (no idea), Doritos chips, sugary cereals and Oreos. After 10 weeks he had lost 27 pounds in weight, his ‘bad’ LDL cholesterol dropped by 20% and his ‘good’ HDL cholesterol increased by 20%. The secret? He only ate a total of 1800 calories a day (compared to an expected 2600 calories)4.
- A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity. J Gerontol A Biol Sci Med Sci. 2015 Sep;70(9):1097-104. https://www.ncbi.nlm.nih.gov/pubmed/26187233
- Caloric restriction delays disease onset and mortality in rhesus monkeys. Science. 2009 Jul 10;325(5937):201-4. https://www.ncbi.nlm.nih.gov/pubmed/19590001
- Impact of caloric restriction on health and survival in rhesus monkeys: the NIA study. Nature. 2012 Sep 13; 489(7415): 10. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3832985/