The trainer for the NBC show “The Biggest Loser” used to think that more exercise was all that was necessary to lose weight. After many years of helping severely obese people lose weight, Bob Harper has concluded that exercise is not the key; diet matters the most.

Not only is Harper helping his clients to feel better and achieve their personal goals, he is also helping them to live longer: much longer. Excess body fat accelerates aging and increases our risk of dying of cancer. Essentially, obesity is an accelerated form of aging and obesity predisposes us to diseases that are common in old age. Why? Obesity reproduces many of the same metabolic conditions that underlie the aging process itself. How? Fat cells produce inflammation; the more you have the more inflammation your body needs to control. Consequently, by elevating the level of inflammatory proteins in the body, obesity increases the risk of breast, colon and lung cancers.

Researchers from the Fred Hutchinson Cancer Research Center in Seattle recently published a report in the journal Cancer Research that investigated whether diet or exercise most effectively modified the levels of inflammatory proteins in overweight or obese women. After twelve months the authors concluded that the greatest weight loss and most significant reduction in the level of inflammatory proteins reductions come only from dieting. The women who participated in an exercise-only program showed no reduction in inflammatory proteins!

Why is exercising so inefficient? The answer lies in understanding how our bodies evolved and the priorities established during this evolution. Our gastrointestinal system uses nearly 70% of all of the energy you consume just to make the remaining 30% available to the rest of your body. Your brain uses about 14% of the available consumed energy, and your other organs that allow you to reproduce and move around your environment (including your muscles and bones) utilize only about 15%. As you can see, very little energy is left over for other tasks in the body. These percentages give you some idea of the priorities—sex and mobility—that billions of years of evolution have set for your body to achieve.  Unless you’re a marathon runner or swimmer, the activity of our musculature is not a big player in calorie consumption.

In a recent study, 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.  As a result of eating just 30% fewer calories, the brains of the monkeys on the restricted diet aged significantly more slowly, developed far fewer age-related diseases, had virtually no indication of diabetes, almost no age-related muscle atrophy, and lived much longer. Most importantly, and consistent with Bob Harper’s conclusions, these monkeys did not exercise the weight off, they simply consumed fewer calories.

Caloric restriction is the only valid, scientifically proven dietary intervention that can slow the aging process, reduce the risk of cancer and improve health.  It’s also much cheaper—you’ll save money on eating so much food and paying for expensive tennis shoes, workout clothing and gym memberships.

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

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