The Obesity Code: Unlocking the Secrets of Weight Loss (Why Intermittent Fasting Is the Key to Controlling Your Weight)

by Jason Fung

Thirty-six young, healthy, normal men were selected with an average height of five foot ten inches (1.78 meters) and an average weight of 153 pounds (69.3 kilograms). For the first three months, subjects received a standard diet of 3200 calories per day. Over the next six months of semi-starvation, only 1570 calories were given to them. However, caloric intake was continually adjusted to reach a target total weight loss of 24 percent (compared to baseline), averaging 2.5 pounds (1.1 kilograms) per week. Some men eventually received less than 1000 calories per day. The foods given were high in carbohydrates, similar to those available in war-torn Europe at the time—potatoes, turnips, bread and macaroni. Meat and dairy products were rarely given. In addition, they walked 22 miles per week as exercise. Following this caloric-reduction phase, their calories were gradually increased over three months of rehabilitation. Expected caloric expenditure was 3009 calories per day.8 Even Dr. Keys himself was shocked by the difficulty of the experiment. The men experienced profound physical and psychological changes. Among the most consistent findings was the constant feeling of cold experienced by the participants. As one explained, “I’m cold. In July I walk downtown on a sunny day with a shirt and sweater to keep me warm. At night my well fed room mate, who isn’t in the experiment, sleeps on top of his sheets but I crawl under two blankets.”9 Resting metabolic rate dropped by 40 perce...