I am pleased to report on another study just published that supports the basic eating principles of the South Beach Diet and solidifies one of our diet’s most important messages: Calories do count, but it’s really the quality of those calories that matters most. Because it is so difficult to do rigorous diet studies in humans (since it is hard to control what they eat), this study, which was published in the June 27 issue of the Journal of the American Medical Association, is important.
During the study, 21 obese male and female participants ages 18 to 40 first had to lose 10 to 15 percent of their bodyweight (about 30 pounds). Once their weight had stabilized, each participant completed four weeks on each of three maintenance diets in a randomly assigned order. (Throughout, the participants were fed food that was prepared by diet experts, which is essential in a controlled study).
The main goal of the study was to assess resting energy (calorie) expenditure and its effects on hunger and weight regain. The secondary goals were to evaluate total energy expenditure, hormone levels, and metabolic syndrome components. As many of you probably know, metabolic syndrome, or prediabetes, is a precursor to diabetes and heart disease and is the main cause of America’s obesity epidemic.
The three diets tested, which included the same number of total calories, were: a low-carbohydrate diet, modeled on the Atkins diet (10 percent of daily calories from carbohydrates, 60 percent from fat and 30 percent from protein); a low-fat diet (60 percent of daily calories from carbohydrates, 20 percent from fat, and 20 percent from protein); and a low-glycemic index diet, designed like the South Beach Diet to keep blood sugar stable between meals (40 percent of daily calories from carbohydrates, 40 percent from fat, and 20 percent from protein).
On the low-carbohydrate diet, the participants used up the most energy (350 more calories per day), but this diet increased their levels of the stress hormone cortisol, which can lead to obesity, insulin resistance, and cardiovascular disease. The low-carbohydrate diet also raised C-reactive protein levels, an indicator of chronic inflammation in the body and another risk factor for heart disease.
On the low-fat diet, participants had the least decrease in calories and, according to the study authors it “exacerbated many of the components of the metabolic syndrome, so insulin resistance, triglycerides [blood fats], and HDL cholesterol [the good cholesterol] were all worse.”
On the low-glycemic index diet, which was based on the Mediterranean-style of eating that is the foundation for the South Beach Diet, the participants burned 150 more calories per day than on the low-fat diet and didn’t show the negative effects on cardiovascular risk. Moreover, the study authors felt that because a low-glycemic index diet, which stresses eating a wide variety of vegetables, fruits, whole grains, and good unsaturated fats, doesn’t eliminate entire classes of foods, it is easier to follow and more sustainable on a day to day basis.
How Does this Affect You?
In short, the study reaffirmed what I’ve said in my books and on this website from day one: The best long-term approach for sustained weight loss and better health is to avoid restriction of any major nutrient—particularly fat and carbohydrates—and to instead focus on the quality of the nutrients you do eat.
We all know that a diet study based on controlled meals is not the same as facing the eating challenges of real life. But it is rewarding to read a study that shows that when it comes down to how various types of diets can affect your metabolism and your health, the basic eating principles of our diet remain sound.