The Fast Diet by Michael Mosley

Based around scheduled, intermittent fasting, the Fast Diet claims to stimulate weight loss, improve your health and lengthen your life. MayoClinic.com cardiologist Martha Grogan says there is some evidence that occasional fasting can benefit your health, but the Fast Diet may not be a good weight-management choice for all dieters. Don't start this diet until you've spoken to your doctor about the possible advantages and disadvantages.

Background

• The Fast Diet was developed in 2012 by British doctor, medical journalist and BBC documentary producer Michael Mosley. After his doctor told him that he was overweight, pre-diabetic and required medication for his high blood cholesterol, Mosley studied the scientific research conducted on fasting and decided to try scheduled calorie restriction on himself. He documented his experiment with intermittent fasting in the BBC documentary, "Horizon: Eat, Fast and Live Longer." While on his fasting plan, Mosley lost nearly 20 pounds, getting his cholesterol and blood sugar levels under control. In 2013, he published "The Fast Diet: Lose Weight, Stay Healthy and Live Longer with the Simple Secret of Intermittent Fasting" with fashion and health writer Mimi Spencer.

The Basics

• The Fast Diet instructs followers to follow a 5:2 rule -- every week, eat normally for five days and fast for two days. On the fast days, you'll consume only one-quarter of your normal daily caloric intake. For the average man, this is about 600 calories; for a woman, it's approximately 500 calories. Mosley and Spencer stress that to be successful on the Fast Diet, you should eat healthy foods in moderation on your five "free" days and focus on foods high in protein and fiber during the two fast days, such as seafood, meat and vegetables. You can split your fast days up throughout the week; you can also split your fast day calories into several small meals or one large meal.

Advantages

• In 2010, a study published in the "International Journal of Obesity" found that women on a 5:2 diet similar to the Fast Diet lost as much weight as women following a typical low-calorie diet. Other studies, including an "American Journal of Clinical Nutrition" review from 2007, have concluded that the type of intermittent fasting encouraged in the Fast Diet may lower your risk of heart disease, cancer and type 2 diabetes, though more research is needed. The plan is flexible and does not restrict dieters from eating particular foods. Knowing that there are only two low-calorie days each week may make it easier for followers to stick with the program long-term.

Disadvantages

• Many of the research studies used to promote the benefits of the Fast Diet, including those that connect fasting with a longer life, were conducted only on animals; the results haven't been repeated in human trials. Diabetics, pregnant or nursing women, children and those who have been diagnosed with an eating disorder like anorexia should not attempt the Fast Diet. Avoid the diet if you're on a prescription medication like the blood thinner warfarin -- Mosely warns the plan may increase the amount of time it takes for your blood to clot. Don't start the program if you're sick or recovering from a medical procedure. On fast days, you may experience fatigue, mood swings, dehydration or trouble sleeping.