Not only does ice offer a calorie-free way to snack—it actually burns calories as your body melts it, says an expert. Gastroenterologist Dr. Brian Weiner steers patients away from fad diets, but his findings on ice have inspired him to write a free e-book of his own: The Ice Diet. "While eating ice, you are serving two purposes," Weiner tells the Atlantic. "You are burning calories and not eating positive-calorie foods." (He calls ice a "negative-calorie food," KPCC notes). By Weiner's calculations, it appears to be "generally safe" for adults to eat a liter of ice a day.
That one liter burns 160 calories, he argues—the number you'd burn by running a mile. A physics writer, however, calculates that you'd need to eat 66 pounds of ice to lose a pound of weight. "Not exactly the most efficient diet plan," writes Andrew Zimmerman Jones at About.com. Weiner, meanwhile, offers a number of safety guidelines: Don't, for instance, eat more than a liter a day. That could be toxic. And be careful eating ice when it's cold out. "I never thought I would be actively promoting and discussing weight loss diets," Weiner writes. "I earnestly hope not to get lumped in with the counter-productive fad diet (snake oil) promoters." (Another interesting recent diet idea? The ice cream cleanse.)