No matter how you look at it, dieting to lose bodyfat is never easy. It demands a rigid decrease in calories. Dieting without exercise is a bad idea and doomed to eventual failure for a number of reasons. For most people, dieting minus working out equals a weight loss that’s about 50 percent fat and up to 50 percent muscle. The loss of muscle, or lean mass, lowers the resting metabolic rate. A slower metabolism means you must take in even fewer calories to continue losing weight. For most people it just doesn’t work.
Numerous studies show that about 97 percent of people who have successfully lost weight on a diet regain the lost weight and then some. Several years ago talk-show host Oprah Winfrey proudly displayed her newfound svelte figure, clad in a pair of size-10 jeans that had been hanging in her closet for years, pushing out a wheelbarrow containing the 67 pounds of fat she’d lost. The fact that Oprah’s weight loss didn’t only consist of fat, however, soon became distressingly clear. She not only regained all the lost weight but packed on a few additional pounds.
Her case was a classic example of yo-yo dieting, defined as a rapid weight loss followed by an equally rapid regain of the lost weight. Usually that involves a large loss of muscle during the diet. It sets you up for diet failure because the drop in resting metabolism that happens when you lose lean mass demands a permanent reduction in calories to maintain the weight’too tough for most people. Oprah’s mistake was too few calories and not enough exercise.
If you can maintain weight loss for five years, your body resets the various hormones related to appetite and energy production, adjusting to a lower natural bodyweight so that it’s no longer a strain to maintain the new weight. Exercising makes it far easier for the body to make those adjustments. Recent studies that have compared low-carbohydrate to other fat-loss diets point up the benefits of the low-carb strategy for the majority of dieters. Various mechanisms have been suggested to explain why’from a greater water loss to better thermogenic effects. More recent studies show that low-carb diets work simply because people on them average 1,000 fewer calories a day.
The question is why people choose to eat less while on a low-carb diet. Some say it’s because low-carb diets lack variety. Others say it’s because insulin control is the cornerstone of low-carb diets: Insulin promotes hunger by lowering blood glucose levels, so it makes sense that controlling insulin would decrease appetite.
The problem with the insulin theory is that protein foods also promote insulin release, though not as much as carbohydrates do. Most low-carb diets emphasize a higher protein intake because protein helps maintain lean mass. Protein is, in fact, a key element of why low-carb diets are successful. Compared with fat or carbs, protein provides far more satiety after a meal. That leads to less eating and fewer calories. Protein stimulates gut hormones that signal the appetite-controlling mechanisms in the brain. The more rapidly the protein is digested, the quicker the appetite is suppressed. That explains why a rapidly acting protein source, such as whey, provides more appetite suppression than casein, another milk protein that is more slowly digested and absorbed.
Protein also helps curb appetites because it has a higher thermogenic effect. Thermogenesis, the conversion of calories into heat, leads to mechanisms that lower appetite. Animal proteins induce a higher thermogenic effect than vegetable proteins, leading to greater satiety.
A recent study shows that maintaining a high-protein diet after fat loss can help maintain the new, lower weight.1 Researchers tracked 113 overweight men and women, aged 18 to 60, who followed a low-calorie diet for a month and maintained the weight loss for six months. After that they were put in a high-protein or a control group, with the protein group getting 30 additional grams of protein. That gave them an 18 percent protein intake, compared to 15 percent in the controls.
During the weight-maintenance phase the high-protein group regained less weight and had slimmer waists than the control group. Weight gain that did occur in the high-pro group consisted of lean mass, while the control group gained some fat. More important, satiety after meals was significantly greater in the high-pro group. Neither group engaged in exercise other than normal activity.
The study implies that staying on a higher-protein diet maintains lean mass and blunts the regain of fat. You get increased satiety, greater appetite suppression and increased thermogenesis from a higher protein intake, and the more favorable body composition that results helps maintain resting metabolism. IM
1 Lejune, M., et al. (2005). Additional protein intake limits weight regain after weight loss in humans. Brit J Nutr. 93:281-89.