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Calorie Restriction

Posted Sep 12 2008 10:45am
(from The New York Times: two rhesus monkeys about the same age, one fed a CR diet,left, the other fed a normal diet)

A number of people have asked about my thoughts on calorie restriction, the movement that follows the notion that the less you eat, the more years you’ll live. The idea is that giving up those hearty meals, those decadent treats, those full-plate or even half-plate servings, you may up your chances at living a longer, healthier life. And, so on the almost-eve of America’s national overeating challenge, I offer some thoughts on calorie restriction. Please keep in mind that these observations/interpretations are from a psychological, not nutritional or biomedical perspective, and that the fact that a clipping on calorie restriction (CR) that I had saved for this post just caught fire on a candle I’m burning at my desk does in no way reflect on my thoughts about CR.

CR involves consuming about 30% fewer calories per day than is generally recommended for one’s height, weight, and body type. The key, though, is that amounts of vitamins, minerals, and other essential nutrients are kept constant (or even enhanced), resulting in a kitchen laboratory of sorts, where scales, measures, and computer monitoring ensure adequate levels of nutrients on a largely barren plate. From what I understand about nutrition, this may not be the easiest task.

Support for CR dates back to 1935, when Dr. Clive McKay, a researcher at Cornell University found that rats fed a CR diet lived approximately 40% longer than their normally-fed counterparts. Similar results have been found in primate populations, where like in mice, scientists are seeing reduced incidences of diabetes, heart disease, cancer, and other ailments with the introduction of CR.

Does CR work in humans? They’re not so sure. The truth is, the scientific community isn’t exactly sure how CR works at all. Still, several hundred thousand people have swapped their cookbooks for cooking scales, their large serving plates for the ceramic equivalent of “just a little bit.” A New York magazine article focuses on Michael, a bona fine calorie restrictor, who at 6’ feet tall and 115 pounds consumes 1,913 calories per day. Exactly 1,913. His dinner, his girlfriend (also a CR devotee) explains, is “‘always 639 calories.’” Other CR followers profiled in the article skip meals or consume a single meal per day.

A New York Times article reports that scientists at Washington University who have studied a group of calorie restrictors have found that “the dieters had better-functioning hearts and fewer signs of inflammation, which is a precursor to clogged arteries, than similar subjects on regular diets.” According to the Times, research published in JAMA has also suggested that those on CR diets have lower body temperatures, lower insulin levels, and fewer indices of chromosomal damage linked to the aging process.

On other hand, the Times reports that:
A mathematical model published last year by researchers at University of California, Los Angeles, and University of California, Irvine, predicted that the maximum life span gain from calorie restriction for humans would be just 7 percent. A more likely figure, the authors said, was 2 percent.
Is it really worth it, to give up (for a lifetime) the decadence, the luxury, the indulgence of food for an extra couple of years? One of the paper’s authors, Dr. Jay Phelan at UCLA says: “‘Calorie restriction is doomed to fail, and will make people miserable in the process of attempting it.’”

As with many enterprises (especially surrounding food and weight), the research may be confounded. People who subscribe to CR are likely to be those who don’t smoke, who don’t drink to excess, who exercise, and who generally engage in a host of other behaviors designed to promote their health. Their results on medical tests do not indicate that CR is ultimately responsible for their good health.

Regarding Phelan’s point above, it’s unclear what the long-term effects of CR in human populations may be. From a psychological perspective, CR does not look much different (at least superficially) from a weight-loss diet. For those who are approaching CR for weight-loss purposes, we may see similar failure rates to other organized approaches that focus on deprivation. CR also looks a lot like the restriction associated with anorexia. Those involved in the CR movement emphasize that the goal is not weight loss and that nutrition takes a paramount role, unlike in anorexia. The Calorie Restriction Society takes a special look at CR vs. anorexia here. Still, eating-disordered thoughts and behaviors may creep up on the unsuspecting CR follower, particularly someone who focuses primarily on the associated weight-loss benefits. We may also see, as Phelan indicates, difficulty adhering to CR and compensatory bingeing, as a result of hunger and a reaction to a constricting, depriving diet without an end in sight.

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