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Low-Carb Comes Out Ahead in Diet Comparison

After Two Years, the Results for Low-Carb Are Great


Updated July 21, 2008

Low-carb? Low-fat? Mediterranean? It seems like every day, there's a new stamp of approval on what diet is best. In a head-to-head match, however, which one would win? A July 2008 study published in the New England Journal of Medicine compared all three.

A group of 322 participants involved in the study were followed closely for two years. On most of the parameters studied, the low-carbohydrate diet was as good as or better than the others.

Let's dig into the most pertinent findings of the study, and my observations about the research and its potential significance for you and other low-carb dieters

The Study

This study of mostly men in Israel took place over a two-year period. The participants were overweight or mildly obese, with BMIs averaging around 30 to 31. They were divided into three groups and given fairly intensive counseling on how to help them follow one of the diets. All study participants worked in the same place, and the workplace cafeteria developed special menus for the three groups that corresponded to the diets they were put on. Offerings were color-coded to make following the assigned diet during the day easy.

The Diets

The three groups followed one of the following diets:

1. Low Fat Diet: A calorie-restricted diet with a maximum of 30% of the calories coming from fat, 10% from saturated fat, and 300 mg of cholesterol daily. "The participants were counseled to consume low-fat grains, vegetables, fruits, and legumes, and to limit their consumption of additional fats, sweets, and high-fat snacks."

2. Mediterranean Diet: A calorie-restricted diet with a goal of a maximum of 35% of the calories from fat, including 2 to 3 tablespoons of olive oil and a few nuts each day. The diet was to be "rich in vegetables and low in red meat, with poultry and fish replacing beef and lamb."

3. Low-Carb Diet: Based on the Atkins Diet, it began at 20 grams of carbohydrate per day, gradually increasing to 120 grams per day "to maintain weight loss." Calories, fat, and protein were not restricted. "However, the participants were counseled to choose vegetarian sources of fat and protein and to avoid trans fat."

The Results

Weight: Of those who finished the 2-year study, the low-carb diet edged out the other two diets, with a sustained average 12 lb. loss compared to 10 lbs. for the Mediterranean diet and 7 lbs. for the low-fat diet. Although the vast majority (86%) of the participants were men, the women had more weight loss on the Mediterranean diet.

LDL ("bad") Cholesterol: All three groups showed a similar small drop, though it was not statistically significant. Interestingly, at six months, the low-carb group showed a slight increase in LDL. However, by the end of the study, their results were between the two other groups.

HDL ("good") Cholesterol: All groups increased their HDL cholesterol, but the low-carb group had an increase that was significantly greater than the other two.

Cholesterol Ratio: Another measurement that has been shown to predict risk of heart disease is the ratio of total cholesterol to HDL cholesterol. The low-carb group showed the greatest improvement in this measure.

Triglycerides: The low-fat group showed no significant change in triglycerides over the two years, while the low-carb group showed a significant drop.

Inflammation: Measures of C-reactive protein, a marker for inflammation, showed a significant and similar drop in both the Mediterranean and low-carb groups, and no significant change in the low-fat group.

Fasting Blood Glucose: The Mediterranean diet showed a drop in fasting blood glucose among people with diabetes, which differed significantly from the slight rise in fasting blood glucose in the low-fat group. The people with diabetes in the low-carb group did not experience a significant change by the end of the study, nor did any of the non-diabetics.

Fasting Insulin: All groups showed a decrease, with no significant differences among the groups.

Insulin Resistance: One measure of insulin resistance showed more of a decrease in the diabetics in the Mediterranean group than those in the low-fat group, but no other differences were shown.

Hemoglobin AIC: In the low-carb group, the H A1C dropped by almost a percentage point in diabetics, the only significant change of any group.

Laura's Analysis of the Study

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