Galveston County Daily News January 29, 2013
Medical Discovery News
By Drs. David Niesel and Norbert Herzog
Americans don’t lack methods of dieting – South Beach, Atkins, Weight Watchers, Nutrisystem, Slim Fast, detoxing, juice cleanses – but not all are healthy. With public health organizations and the media constantly remarking on the obesity epidemic in the U.S., new studies on approaches to start and maintain weight loss couldn’t come at a better time.
A new study conducted at Boston Children’s Hospital and published in the Journal of the American Medical Association compared the weight loss and subsequent weight maintenance of three popular dieting approaches: low-carb diets, low-fat diets and low-glycemic diets.
When someone decreases the amount of calories they consume, the body’s metabolism slows, reducing the use of calories and contributing to weight gain. This can work against the goal of losing weight and keeping it off. So researchers examined the affect of these popular dieting approaches on long-term weight loss.
The Boston study followed a group of overweight and obese adults aged 18 to 40 for 10 weeks. After achieving an initial 10 to 15 percent weight loss, researchers placed subjects on one of the three diets and looked for changes in their metabolism and weight maintenance. These diets were isocaloric, meaning all subjects consumed the same number of calories despite being on the different diet plans.
The low-carb diet had the most pronounced effect on metabolism with the best resting energy expenditure (REE) and total energy expenditure (TEE). But the low-carb diet also resulted in some undesirable side effects, like high levels of the stress hormone cortisol, which can lead to diabetes, and biochemical markers like CRP, which are associated with inflammation and heart disease.
Similarly, the low-fat diet produced the hormone leptin, which is associated with hunger and could lead to weight gain. In contrast, the low-glycemic diet allowed stable blood sugar and metabolism levels without elevations in stress hormones and other negative biochemical markers. What type of food a person eats affects their metabolism, and a person’s metabolic index determines how many of those calories will be burned.
The low-glycemic diet derives 40 percent of calories from carbohydrates, 40 percent from fats, and 20 percent from proteins. The diet uses a number of fiber-rich foods like beans, non-starchy vegetables, fruit, and whole grains; lean protein sources like fish and skinless poultry; and healthy fats from nuts, avocados, and certain vegetable oils. These foods require a longer time to digest and absorb, leaving people feeling fuller for a longer time.
The main conclusion of this study is that a calorie is not just a calorie in the context of weight loss or maintenance. Successful dieting and weight maintenance requires behavioral modifications in addition to caloric restriction, and individuals should consult their physicians about their weight-loss goals and diet plans.
Medical Discovery News is a weekly radio and print broadcast highlighting medical and scientific breakthroughs hosted by professor emeritus Norbert Herzog and professor, David Niesel, biomedical scientists at the University of Texas Medical Branch at Galveston. Learn more at www.medicaldiscoverynews.com.