It has risen to new prominence recently thanks to the American plastic surgeon Dr James Johnson's recent book The Alternate Day Diet.
But what does alternate day fasting really mean?
Unlike most diets with a plan to follow day in, day out, on alternate day or intermittent fasting diets you'll have one completely normal day followed by a day of eating much less.
Some alternate day fasting diets suggest two days of fasting a week instead (the 5:2 day fasting diet, for example), and 'fasting' can mean anything from total abstinence to half of your recommended daily intake. Dr Johnson's book recommends eating 20% of your normal calorie intake (that's just 400 calories for the average woman).
But the principle is the same - it doesn't matter what you eat on either day, as long as you fast.
So, what are the benefits? The idea that restricting calories leads to weight loss and health benefits including longer life has been around for decades, but intermittent fasting makes it much easier to work into normal life.
Fasting intermittently places just enough stress on the body to trigger SIRT1, the 'skinny gene'. This speeds up your metabolism, releases fat to be used as energy, and turns off another gene that controls fat storage. In the long term, it's actually harder for your body to store fat.
Studies show that it could also have a positive effect against conditions including type 2 diabetes, heart disease and Alzheimer's.
Intrigued? Find out more about alternate day fasting and how it could help you...
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