Intermittent fasting has blown up in the past year, but scientists are just starting to figure out how it can help you lose weight. In one study from the University of Illinois at Chicago, researchers compared obese people in a traditional weight loss group and fasting group. For the experiment, the calorie-restricted group simply reduced the amount of calories they ate by 25 percent each day. The fasting group, however, alternated days: they ate 25 percent of the calories they needed one day between 12 and 2 p.m., and then had feast days the next, where they ate 125 percent of their required calories.
Very low calorie diets provide 200–800 calories per day, maintaining protein intake but limiting calories from both fat and carbohydrates. They subject the body to starvation and produce an average loss of 1.5–2.5 kg (3.3–5.5 lb) per week. "2-4-6-8", a popular diet of this variety, follows a four-day cycle in which only 200 calories are consumed the first day, 400 the second day, 600 the third day, 800 the fourth day, and then totally fasting, after which the cycle repeats. These diets are not recommended for general use as they are associated with adverse side effects such as loss of lean muscle mass, increased risks of gout, and electrolyte imbalances. People attempting these diets must be monitored closely by a physician to prevent complications.
"When going out for fast food, I used to get the large-size value meal. Now, I satisfy a craving by ordering just one item: a small order of fries or a six-piece box of chicken nuggets. So far, I've shaved off 16 pounds in seven weeks, and I'm on track to being thinner than my high school self for my 10-year reunion later this year." —Miranda Jarrell, Birmingham, AL