Almost everyone can benefit from intermittent fasting (IF), which—as its name implies—means alternating between periods of eating and not eating for various amounts of time. "Fasting is the oldest dietary intervention in the world," writes Dr. Jason Fung in The Complete Guide to Fasting. "Because it differs from conventional dieting in so many important ways, fasting carries many distinct advantages."
Among them, fasting is simple, free, convenient, effective, and allows you to enjoy life’s occasional indulgences. You can do IF on almost any plan, whether you’re vegan or paleo, and it gives your overworked digestive system a much-needed break.
IF challenges conventional health theories: Many practitioners skip breakfast, don’t count calories, and go long hours—sometimes days—without eating. They think when you eat may be just as important as what you eat. And it gets results. Intermittent fasting’s numerous benefits include weight loss and chronic disease management.
At the same time, no one plan works for everyone, and that includes IF. Even Fung notes certain people shouldn’t do IF, including pregnant or breastfeeding women, underage people, and malnourished folks. He advises others like people with type 1 diabetes to proceed cautiously with fasting. While you can usually work with a credentialed health care expert and modify fasting to your condition, I’ve found people with these five issues should think twice about, and—in one case—absolutely avoid intermittent fasting: