6 April 2006. A study on the benefit of caloric restriction in humans, first covered in our summary of the American Aging Association meeting in Oakland, California, last year, was published in yesterday’s Journal of the American Medical Association. Eric Ravussin and colleagues at Louisiana State University, Baton Rouge, report that 6 months of caloric restriction (CR), or caloric restriction plus an exercise regimen, led to significant reductions in both fasting insulin and core body temperature, changes that have been associated with increased longevity in other mammals. People in either CR regimen also had significantly less DNA damage after the 6-month trial, supporting the theory that burning more calories leads to the production of more reactive oxygen species, which then go on to damage DNA and proteins. Reactive oxygen species have long been suspected of playing a role in neurodegenerative disorders such as Alzheimer and Parkinson diseases.
The CR paper comes back-to-back with an analysis of the prevalence of obesity in the United States over the 6-year period from 1999 to 2004. Cynthia Ogden and colleagues at the Centers for Disease Control and Prevention, Hyattsville, Maryland, report some sobering statistics. The authors calculated that in 2003-2004, over 65 percent of adults in the U.S. were overweight, almost half of these being obese. Even more troubling is that the trend is toward increasing girth and not just in adults, but in children of both sexes as well. Over 17 percent of children and adolescents are now overweight, up from just under 14 percent in 1999-2000, and one-third of all children and adolescents are either overweight or at risk of being overweight.
As Luigi Fontana from Washington University School of Medicine, St. Louis, writes in an accompanying JAMA editorial, “excessive adiposity is a serious problem, and is associated with insulin resistance, dyslipidemia, low-grade inflammation, and changes in levels of growth factor and other hormones that play a role in the development of diabetes, atherosclerosis and some types of cancer.” The Comprehensive Assessment of the Long-Term Effects of Reducing Intake of Energy (CALERIE) trial conducted by Ravussin and colleagues is the first to report a significant decline in DNA damage in response to calorie restriction in humans, Fontana adds. And while he predicts most people would not adopt a calorie-restricted diet, he suggests that such studies may reveal mechanisms of aging that can be exploited to modify the effects of aging. Read our conference summary for more background on the CALERIE Trial.—Tom Fagan.
Heilbronn LK, de Jonge L, Frisard MI, DeLany JP, Larson-Meyer DE, Rood J, Nguyen T, Martin CK, Volaufova J, Most MM, Greenway FL, Smith SR, Deutsch WA, Williamson DA, Ravussin E. Effect of 6-month calorie restriction on biomarkers of longevity, metabolic adaptation, and oxidative stress in overweight individuals—A randomized controlled trial. JAMA. April 5, 2006;295:1539-1548. Abstract
Ogden CL, Carroll MD, Curtin LR, McDowell MA, Tabak CJ, Flegal KM. Prevalence of overweight and obesity in the United States, 1999-2004. JAMA. April 5, 2006;295:1549-1555. Abstract
Fontana L. Excessive adiposity, calorie restriction, and aging. JAMA. April 5, 2006;295:1577-1578. Abstract