The New Science Behind Diet and Weight Loss?It’s All about Diversity

It’s the time of year to think about achieving a healthy weight. Surveys say that almost half of all women pledge to lose weight for their New Year’s resolutions. It’s a worthy endeavor, since about two-thirds of U.S. adults are overweight and one-third are obese (the obese also fall into the overweight category), which brings a higher risk of diseases like diabetes, heart disease, stroke, osteoarthritis, sleep apnea, certain cancers, psychological disorders, increased surgical risk and increased mortality. With so many reasons to maintain a healthy weight, it’s not difficult to understand why the notion of weight loss is so popular at this time of year. What is difficult to understand is how to navigate the sea of diets that fill book store shelves and pour forth from the Internet. A recent Google search yielded more than 34 million results for the search terms “weight loss diets.” Many claim to be “the one and only diet,” but that’s not what scientific research demonstrates. EN investigated the most recent research in weight loss and found a recurring theme: There’s more than one way to achieve successful weight loss.

Lessons from the National Weight Control Registry (NWCR). Established in 1994, the NWCR comprises the largest investigation of long-term, successful weight loss ever, tracking and examining weight loss strategies of over 5,000 people. NWCR found remarkable diversity in what works for people. Here are some highlights:

  • 45 percent lost weight on their own; 55 percent lost weight using some type of program.
  • 98 percent modified food intake in some way to lose weight.
  • 94 percent increased physical activity, most commonly by walking.
  • While there is variety in how people maintain weight loss, most maintain a low-calorie, low-fat diet with high levels of activity.

The macronutrient divide. Recent studies explore the effects of macronutrient (carbohydrates, fat and protein) distribution on weight loss, discovering that weight loss really boils down to calories. The DIRECT (dietary intervention randomized controlled trial) two-year study looked at success and adherence among 322 moderately obese subjects in one of three groups: low-fat, Mediterranean or low-carbohydrate diets. The researchers found that overall compliance was 90 percent in the low-fat group with 6.4 pounds weight loss, 85 percent in the Mediterranean group with 9.7 pounds weight loss, and 78 percent in the low-carb group with 10.3 pounds weight loss. They concluded that the weight loss?not the diet?at the six-month point was the main predictor of long-term success in weight loss. These findings were published in the Journal of the American College of Nutrition in April 2009.

Australian researchers looked at whether macronutrient spread of the diet played a role in one-year weight maintenance in overweight and obese subjects in a November 2009 study in the American Journal of Clinical Nutrition. After beginning with a very low-calorie diet, the subjects were divided into a low-carb or low-protein diet group. Both groups maintained an average weight loss of 14.5 kilograms (1 kilogram=2.2 pounds), with no significant difference in weight loss noticed between the two groups.

Diets with different macronutrient composition were compared in a trial that included 811 overweight adults, which was published in The New England Journal of Medicine in February 26, 2009. The subjects were assigned to one of four diets with varying percentages of total calories from fat, protein and carbohydrates. Group and instructional sessions were offered. At six months, subjects assigned to each diet had lost an average of 6 kilograms (kg), but they began to regain weight after 12 months. The average weight loss among the subjects who completed the two-year trial was 4 kg. The researchers concluded that reduced-calorie diets resulted in weight loss regardless of the macronutrient spread. Katherine McManus, M.S., R.D., director of nutrition at Brigham and Women’s Hospital in Boston, worked on the research team. She reports, “An important point is that over a longer time, the bottom line for the people that lost weight and maintained weight loss was total calories. Our study supported that a healthy weight loss plan can be individualized, culturally-sensitive and accommodate a wide variety of preferences.”

Beyond food. Successful weight loss goes beyond diet choice. Factors like eating behavior, support and exercise are paramount. In an October 2009 study published in Annals of Behavior Medicine, researchers compared weight-loss maintainers with obese subjects, discovering that weight-loss maintainers were more physically active, showed more dietary restraint and controlled environmental factors like high-fat foods at home. A University of Alabama study published in October 2009 in the research journal Obesity highlighted the importance of exercise. As little as 80 minutes per week of aerobic or resistance training had modestly positive effects on preventing weight regain and, more importantly, prevented regain of potentially harmful visceral fat at the one-year point after diet-induced weight loss.

Taking diet another step. “We have evidence over the last 10 years that the amount of carbohydrates, fat and protein doesn’t really make any difference in weight loss,” says Christopher Gardner, Ph.D., who researches weight loss at Stanford Prevention Research Center. “It’s much more complicated than just low-carb and low-fat. You can tell 20 different people to eat low-fat and they will not eat the same.” Gardner explains that the addition of large amounts of sugars to foods blurs the issue of diets like low-carb and low-fat. A low-fat diet can be filled with processed, sugary foods bearing a “low-fat” label (think sweetened low-fat yogurt), or it can be rich in whole plant foods. He proposes a different way to look at weight loss that focuses on a return to unprocessed, sustainable, whole foods. Gardner concedes that this sort of weight loss diet isn’t researchable in our current science model, but he urges people to “Relax, go back to real food, grow some of your own vegetables and use common sense.” Since research indicates that there’s more than one way to lose weight, it sounds like smart advice.

? Sharon Palmer, R.D.

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