Caloric restriction (CR), which is reduced calorie intake without essential nutrient deficiency (i.e. a state of undernutrition without malnutrition) has been associated with improved cognition, a slowing of overall brain aging, and protection against neurodegenerative diseases - at least in animal models. Currently, however, very little is known about the benefits of CR on the human brain, especially if the CR diet is initiated later in life. Most of the recent animal studies were initiated when the animals were rather young in order to detect the largest possible benefits.

Although the exact mechanisms underlying the beneficial effects of CR are not known, a calorically restricted diet is known to impart beneficial effects on health and extend lifespan in a large variety of species ranging from worms to monkeys.   Evidence suggests that a reduction in inflammatory processes underlies at least part of CRs beneficial effects along with decreases in oxidative stress. I've discussed the role of these factors in previous blogs.

Interestingly, low body weight associated with starvation in both intentional (e.g. anorexia nervosa, bulimia, and hunger strike) and unintentional cases (war) is linked with smaller brain volume and does not show significant beneficial effects.

In a recently published study (Bendlin et al., Neurobiology of Aging, 2012), a large group of monkeys, ranging in age from middle-aged adults to the quite elderly, were fed only 70% of their free-feeding diet for about 15 yrs.  Essentially, for someone eating a 2000 calorie per day diet, this would be about 600 fewer calories per day; for comparison, 600 calories would be about one cup of roasted almonds, or a 100 gram bar of dark chocolate, or a typical Cold Stone Creamery dessert (with the M & M's!). 

As a result of eating just 30% fewer calories, the brains of the monkeys on the CR diet aged significantly more slowly.  Although several brains regions showed benefits, those brains regions that evolved most recently, such as the frontal lobes, and therefore tend to be more vulnerable to the consequences of aging, showed the greatest beneficial response to CR.  Monkeys on the CR diet have previously been shown to develop far fewer age-related diseases, have virtually no indication of diabetes, almost no age-related muscle atrophy, and live much longer (Colman et al., Science, 2009).

Take notice of the crucial fact that these monkeys did not exercise the weight off, they simply consumed fewer calories.  Unless you plan on becoming a long distance runner, or something similar, exercising is never going to be as beneficial to your brain and body as restricting the number of calories you consume!  

© Gary L. Wenk, Ph.D. Author of Your Brain on Food (Oxford, 2010)

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