Fast & Feast Diet

In the feast or fast diet plan, you eat what you want during feast days and restrict calories during fast days. This diet actually goes by many names, including the alternate-day diet, the up-day down-day diet and the intermittent fasting diet. If you want to give it a whirl, make sure to consult a doctor first -- especially if you have a health condition or take medicines.

Sandwich on a bun (Image: ITkach/iStock/Getty Images)

Features

The premise for this diet is fairly simple. On feast days, you eat whatever you want but avoid overstuffing yourself. On famine days, reduce caloric intake 20 to 50 percent. Some versions of the plan have an induction phase in which you consume only 500 calories on famine days for the first two weeks.

Function

This diet is supposed to trigger a "skinny" gene that boosts your body's fat burn, according to Jerome Burne's November 24, 2009 article, "Feast or Famine," in the Daily Mail newspaper. This gene, Sirt1, triggers fat loss, says Frédéric Picard, lead author for a study published in the journal "Nature."

Effects

Preliminary research indicates that this diet can trigger weight loss, says Krista A. Varady, lead author for a study published in the "The American Journal of Clinical Nutrition." Varady tried the diet over 10 weeks on 16 obese people. Dieters lost weight, lowered their levels of the "bad" high-density lipoprotein cholesterol and lowered blood pressure. Dieters in the study lost between 10 and 30 lbs.

Theories/Speculation

This diet is promoted by Dr. James B. Johnson, a plastic surgery instructor at the Louisiana State University Health Sciences Center School of Medicine. He's the author of "The Alternate-Day Diet" as well as several articles about the diet. Johnson, who follows the diet himself, claims the diet can reduce inflammation, improve insulin resistance, lower free-radical stress, and improve cellular energy production. However, it's unknown if some of the data Johnson has collected will hold up to scientific standards, notes the Diet Spotlight website. Much of the science backing this theory relies on animal studies, according to the Diet Choices website. However, such studies do show that animals on calorie-restricted diets are healthier, and that restricting calories every other day instead of all the time brings about the benefits Johnson lists, Burne notes.

Expert Insight

This diet may actually be easier to stick to than others that restrict calories because you won't feel deprived, according to Burne. Varady notes that adherence to the diet was high during her study. Healthy food choices are promoted, including fruits and vegetables, on both feast and famine days, though there's not a specific meal plan to follow. Exercise is recommended as well, according to Burne.