The Redemption of Protein: Good for Weight, Glucose, and Blood Fats

As popular as they are, high-protein diets have remained controversial since they were popularized by Robert Atkins, MD, in the early 1970s. Do they really help people lose weight? Improve their blood sugar? Or lower blood fats?

The answer to all those questions is yes, according to a well-controlled study of 322 moderately obese middleage men and women. The study was conducted at a research center with an on-site medical clinic and cafeteria in Dimona, Israel – enabling exceptional dietary and medical follow-up of the participants.

Iris Shai, PhD, RD, of Ben-Gurion University led a team of international researchers that included physicians from the Harvard Medical School and University of Leipzig, Germany.

The men and women in the study ate (1) a highprotein, low-carb diet, (2) a Mediterranean-style diet, or (3) a traditional low-fat, low-calorie diet for two years. Not surprisingly, people in the high-protein, low-carb group consumed the fewest carbohydrates, but participants of all three groups consumed approximately the same number of calories.

People in all three groups lost weight, but those eating the high-protein, low-carb diet lost the most – an average of 12 pounds. People on the Mediterranean diet lost 10 pounds, and those on the low-fat diet lost more than seven pounds. Abdominal fat decreased the most among people on the high-protein, low-carb diet.

For people on the high-protein diet, levels of HbA1c – which provides an average blood sugar level over about four weeks – decreased by a significant 0.9 percent, a decline that was approximately twice that of people following either the Mediterranean or low-fat diet. For people with type 2 diabetes, the high-protein diet led to an 18 mg/dl decline in fasting blood sugar. However, on the Mediterranean diet, people with diabetes had an even greater 33 mg/dl decrease in fasting blood sugar.

Meanwhile, people on the high-protein, low-carb diet averaged a 23.7 mg/dl decrease in triglycideride levels – almost 10 times greater than those on the low-fat diet. Levels of the “bad” low-density lipoprotein (LDL) form of cholesterol decreased in both the high-protein and Mediterranean diet groups, but not in the low-fat group. At the same time, levels of the good high-density lipoprotein (HDL) cholesterol increased about 30 percent in the high-protein group, compared with the other two groups.

In addition, levels of high-sensitivity C-reactive protein (CRP), a marker of inflammation, decreased substantially in the high-protein and Mediterranean diet groups. People on the high-protein diet averaged a 29 percent decrease in CRP levels, and those on the Mediterranean diet had a 21 percent decrease in CRP.

In a separate study, researchers at Bleking Hospital, Karlshamn, Sweden, tracked the progress of 31 people on either a high-protein, low-carb diet or a high-carb diet over almost four years. Two-thirds of the high-carb group switched to a high-protein, low-carb diet after the first six months of the study.

By the end of the study, people following a high-protein, low-carb diet had an average decrease from 8 percent to 6.8 percent in their HbA1c levels. They also lost an average of 17.6 pounds of body weight.

References: Shai I, Schwartzfuchs D, Henkin Y, et al. Weight loss with a low-carbohydrates, Mediterranean, or low-fat diet. New England Journal of Medicine, 2008;359: 229-241. Nielsen JV, Joensson EA. Low-carbohydrate diet in type 2 diabetes: stable improvement of bodyweight and glycemic control during 44 months follow-up. Nutrition & Metabolism, 2008;5:14.