Fasting two days each week induces your body to burn fat and promotes weight loss, say writer Mimi Spencer and Dr. Michael Mosley, the people behind the 5:2 diet, also known as the Fast diet. Some scientific research supports Spencer's and Mosley's premise, but you should talk to your doctor before beginning any type of weight-loss program, especially if you have a chronic medical problem.
While you're on the Fast diet, you'll eat regularly for five days each week and fast on the remaining two days. For men, this means limiting your total caloric intake on fast days to 600 calories; women are allowed 500 calories. The fast day calories can be consumed all in one meal or through several small meals spaced throughout the day. Arrange the two fasts on consecutive days or split them up throughout the week.
Sample Fasting Menu
There are no limits on what you can eat on the regular or fast days of the 5:2 diet, but the authors suggest focusing on foods with a low glycemic index -- fruit, nonstarchy vegetables, whole grains and beans, for example -- and lean proteins like skinless poultry, fish or nuts. A sample fast day on the diet could feature a breakfast of strawberries and ricotta cheese, an apple around lunchtime, and couscous, vegetables and tofu for dinner.
A study published in 2013 in "Nutrition Journal" reported that a diet including alternate fast days aided weight loss and reduced the risk of cardiovascular disease in both normal weight and overweight adults. However, the researchers pointed out that additional, larger studies are needed to confirm these results. The 5:2 diet is easy to understand, can be followed by people with any type of dietary restriction and does not forbid any type of food. "The Fast Diet" book and "The Fast Diet Cookery Book" provide fast day recipes and menus to make it easier to keep track of your daily calorie count.
Dietitian Cynthia Sass cautions that the Fast diet may disrupt sleep patterns or encourage some followers to eat excessively on the nonfast days. It may also contribute to nutritional deficiencies if you aren't careful to stick to nutrient-dense foods on fast days. Athletes and people with demanding schedules may find that the fast days don't allow enough calories to supply them with adequate energy. Women who are pregnant or nursing, people with a history of eating disorders and individuals recovering from surgery or taking certain medications, including warfarin, should not attempt the Fast diet.