A new mouse study suggests fasting every other day can help fend off diabetes and protect brain neurons as well as or better than either vigorous exercise or caloric restriction. The findings also suggest that reduced meal frequency can produce these beneficial effects even if the animals gorged when they did eat, according the investigators at the National Institute on Aging (NIA).
"The implication of the new findings on the beneficial effects of regular fasting in laboratory animals is that their health may actually improve if the frequency of their meals is reduced," says Mark Mattson, Ph.D., chief of the NIA's Laboratory of Neurosciences. "However, this finding, while intriguing, will need to be explored further. Clearly, more research is needed before we can determine the full impact that meal-skipping may have on health."
In the study*, published in the Proceedings of the National Academy of Sciences Online Early Edition the week of April 28, 2003, Dr. Mattson and his colleagues found mice that were fasted every other day but were allowed to eat unlimited amounts on intervening days had lower blood glucose and insulin levels than either a control group, which was allowed to feed freely, or a calorically restricted group, which was fed 30 percent fewer calories daily than the control group. Despite fasting, the meal-skipping mice tended to gorge when provided food so they did not eat fewer calories than the control group. This finding in mice suggests that meal-skipping improves glucose metabolism and may provide protection against diabetes, Dr. Mattson says.
In the same study, mice on these three diets were given a neurotoxin called kainate, which damages nerve cells in a brain region called the hippocampus that is critical for learning and memory. (In humans, nerve cells in the hippocampus are destroyed by Alzheimer's disease). Dr. Mattson's team found that nerve cells of the meal-skipping mice were more resistant to neurotoxin injury or death than nerve cells of the mice on either of the other diets.
Previous studies by Dr. Mattson and his colleagues suggested that nerve cells in the brains of rodents on a meal-skipping diet are more resistant to dysfunction and death in experimental models of stroke and other neurological disorders including Parkinson's, Alzheimer's and Huntington's diseases. Dr. Mattson also has found that meal-skipping diets can stimulate brain cells in mice to produce a protein called brain-derived neurotrophic factor (BDNF) that promotes the survival and growth of nerve cells.
Dr. Mattson and his colleagues are currently studying the effects of meal-skipping on the cardiovascular system in laboratory rats. The findings of this study, which compares the resting blood pressures and heart rates of rats that were fasted every other day for six months with rats allowed to eat unlimited amounts of food daily, should be available soon.
*RM Anson, Z Guo, R de Cabo, T Iyun, M Rios, A Hagepanos, DK Ingram, MA Lane, MP Mattson, "Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from caloric intake," Proceedings of the National Academy of Sciences Online Early Edition the week of April 28, 2003; www.pnas.org/content/100/10/6216.abstract?sid=875e0d26-b3ed-4cd4-9baa-d3abbde304a8  .
The NIA leads the Federal effort supporting and conducting biomedical, clinical, social, and behavioral research on aging. This effort includes research into the causes and treatment of Alzheimer's disease, Parkinson's disease, stroke and other neurodegenerative disorders associated with age. Press releases, fact sheets, and other materials about aging and aging research can be viewed at the NIA's general information Web site, www.nia.nih.gov .