Best diet: High protein and low good carbs

By Dr. Ananya Mandal, MDNov 24 2010

A group of European researchers have found that eating more protein and fewer refined carbohydrates helps to stay within normal weight. The team showed that men and women who had lost at least eight percent of their body weight on a low-calorie diet were kept on a maintenance diet high in protein and low in refined carbohydrates for six months. They were least likely to regain any weight, and were also the least likely to drop out of the study.

The participants were divided into groups eating varying amounts of protein, a moderate amount of fat, and different quantities of carbohydrates categorized as either high or low on the glycemic index. Glycemic index or GI is a measure of how fast a food is converted to sugar in the blood. High-GI foods, like white bread and other foods containing refined carbs, produce a quick spike in blood glucose, while low GI foods, like whole grain breads, cause a slower increase in blood sugar that lasts for a longer period of time.

The study was published in the New England Journal of Medicine. Dr. Thomas Meinert Larsen of the University of Copenhagen, one of the study’s authors said the results “translate into different dietary advice for more broad use probably still has to be discovered because glycemic index is really not an easy and straightforward tool to use for most people I would say.”

Larsen and his colleagues initially enrolled 773 men and women and their families in eight different western European countries. These families were randomly assigned to one of five different weight-maintenance diets for 26 weeks. None restricted calories, but four of the diets did dictate the proportion of proteins, fats and refined carbs that should make up daily food intake. A group that ate without restrictions served as control. Rest of the groups were:

• low-protein, low-GI diet
• low-protein, high-GI diet
• high-protein and low-GI diet
• high-protein and high-GI diet

The low protein groups consumed 13 percent of calories as protein; in the high-protein groups, 25 percent of total energy consumed was protein. People in all of the groups could eat as much as they liked. To make sure they followed their diets, the study participants were counselled on what foods to prepare, submitted food diaries and underwent urine tests to check the amount of protein they consumed. A small portion of the participants had their meals prepared for them.

Results showed that 71% adults completed the study. 26 percent of people in the high-protein or low-GI groups dropped out of the study, 37 percent of people in the low-protein, high-GI group quit. The 548 people who stuck to the diet ate a low-protein, high-GI diet gained a significant amount of weight (1.67 kilograms, on average, or about 3.7 pounds). These people gained about a kilogram less than those in the low-protein groups; the same was true for the low-GI versus high-GI groups.

Dr. David Ludwig, the director of the Optimal Weight for Life Program at Children's Hospital Boston said losing weight on the short term is easier than maintaining it over time. Ludwig co-authored an editorial accompanying the study. He said, “The nature of the diet and how that diet affects our underlying biology may have a lot to do with how likely we are to comply, to remain on the diet.” People on the high-protein, low-GI diets “appear to like this way of eating more, perhaps because they were feeling less hungry and more energetic...or just noticing that they were doing better. There’s nothing that succeeds like success when it comes to weight loss,” he added. He said this could be an easy diet to follow. “Adding a serving of nuts and beans to the diet every day and cutting back on the refined grains will produce at least as much dietary change as they obtained in the study…If everyone in America could cut back on two servings of refined grains and substitute that with one serving of nuts and one serving of beans, the impact on public health would really be potentially enormous, and that's a change within everyone’s reach.”

James O. Hill, director of the Center for Human Nutrition at the University of Colorado, who was not a part of the team observed, “There is not much difference among the groups right now.” But he commended the team for focusing on weight maintenance, an often-overlooked aspect of weight loss. “This is the kind of research that ought to be done,” he said.

Nutrition researchers have not reached a consensus about how much protein and glycemic index matter for weight loss and weight control. Among children in the study high-protein, low-glycemic-index food consumption reduced the 46% overweight kids to 39% in six months. These results were published this month in the journal Pediatrics.