The theory behind this diet is that when you fast, your body starts using fat stores for energy, resulting in weight loss.
Fasting to improve your health isn't a new idea – Hippocrates and Plato were both proponents of it – but the idea of intermittent fasting to lose weight has become popular in recent years with the publication of books such as "Eat Stop Eat" by Brad Pilon and "The FastDiet," by Michael Mosley and Mimi Spencer.
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Potential health benefits
By severely limiting your calories during two days of the week, you'll presumably be eating fewer calories overall, which should help you lose weight. In addition, it might be an effective diet for people who have a hard time sticking to a restrictive diet day after day.
Several studies of intermittent fasting diets show that following the diet for several weeks can result in weight loss, but it's not clear how long the results last, according to WebMD. In addition, other research shows that the diet may improve cholesterol levels, which can yield cardiovascular benefits. It may also improve the way your body uses insulin, so it could be effective in helping to prevent type 2 diabetes.
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Potential health risks
If you find yourself starving after a day of near-fasting, you may be ready to inhale almost all the food you can get your hands on. That, of course, won't be good calorie-wise, and your hunger may also cause you to make poor food choices and reach for fatty comfort foods.
Some studies have raised red flags, according to Scientific American. One found that rats subjected to the diet experienced increased blood glucose levels as well as the presence of compounds that can damage cells. In another, the rats developed stiff heart tissue, which interfered with the heart's ability to pump blood.
While the diet may be appropriate for some people, you should definitely talk to your doctor before starting it, especially if you already have Type 2 diabetes. It's also not appropriate for women who are pregnant or trying to get pregnant, for people who have type 1 diabetes, or for people who have certain other medical conditions or who are taking certain medications.