Is fasting a long-ignored health savior for diabetics or a possible cause?
Fasting and Diabetes. Plus: How Much Exercise Does It Take to Keep a Heart Strong?
weight gain may be driven by not only what we eat but also our tendency to eat all day long. That’s the thinking behind the weight-loss trend of intermittent fasting, which has grown in popularity in the past few years. An increasing number of health professionals are also prescribing fasting to people with type 2 diabetes, which currently afflicts more than 29 million people in the United States. Yet a recent study warns that going for long stretches without eating could cause the very damage it’s supposed to prevent.
Type 2 diabetes is triggered in part by unhealthy eating, which renders the body resistant to insulin, a hormone produced by the pancreas. Without insulin, sugar from food can’t enter our cells, leaving the blood with an excess amount of sugar. At first, the pancreas compensates by making more insulin, but eventually the demand wears it out. Diabetics then become dependent on insulin injections to control their blood sugar.
Dr. Jason Fung is convinced that fasting undoes that cycle: Not eating, after all, reduces blood sugar. And, as he points out, it’s something we naturally do already, when we sleep. “It’s supposed to be part of everyday life,” says Fung, a kidney specialist who co-founded the Toronto-based Intensive Dietary Management Program and wrote The Obesity Code and The Complete Guide to Fasting. Fasting can also send the body into ketosis, in which it burns fat rather than sugar. That helps with losing weight, which also aids in slowing diabetes.
Several recent studies support this thinking. Research published June 5 in the scientific journal Cell Metabolism found that eating only between 8 a.m. to 2 p.m.—instead of the more common 8 a.m. to 8 p.m.—helped people with early signs of diabetes respond better to their body’s natural insulin. The schedule also reduced blood pressure and appetite, two factors that worsen diabetes.
But some researchers are calling for caution, including Ana Bonassa, from the University of São Paulo, in Brazil. She and her colleagues presented a study in which rats subjected to intermittent fasting showed an increase in fat tissue, with damage to insulin-releasing cells in the pancreas. Those effects, Bonassa says, “could lead to diabetes and serious health issues.” Fung disputes the result. As with all animal-based clinical research, it isn’t necessarily applicable to men and women. Furthermore, humans have gone for long periods without eating for most of our history. “If fasting gives us diabetes,” he says, “then cavemen should have had a lot of it.”