A keto diet - where you flip your metabolic switch, going from burning sugar to burning fat for fuel - leads to significant weight loss and other potential health benefits. But one of the challenges of a standard low-carb, high-fat keto diet is that it can be hard to stick to. Dr Michael Mosley's number-one bestselling Fast 800 Keto is different. It is more effective than a conventional keto regime, healthier and more sustainable. The secret to this new approach is that it combines keto with intermittent fasting, which means you go into ketosis faster, while also being able to enjoy delicious Mediterranean-style food.