Go against the grains, diet study suggests: low-carb beats low-fat in weight loss, cholesterol

Science News, August 16, 2008 by Nathan Seppa

Talk about taking a hit in the breadbasket. A new study finds that a low-carb diet results in greater weight loss and better cholesterol than a low-fat regimen that promotes a lot of grains and fruits. A Mediterranean diet yielded results between the two, researchers in Israel report in the July 17 New England Journal of Medicine.

By conducting a trial within a single workplace, the scientists kept 85 percent of study participants on their respective diets for a full two years, a coup among diet studies. High dropout rates have historically skewed the results of such studies.

While people lost at least some weight on all three diets, the differences were statistically significant. "The old food pyramid is going to get turned on an angle," says study coauthor Iris Shai, a nutritional epidemiologist at Ben-Gurion University of the Negev. "Maybe now it's a little more questionable that we should be basing our diets on carbohydrates."

The team recruited 322 overweight people, average age 52 and mostly men, and randomly assigned them to one of the diets. Some 272 completed the study.

The low-fat diet closely adhered to guidelines developed by the American Heart Association, which recommends plenty of low-fat grains, vegetables, fruits and legumes. Dietitians counseled participants to strictly limit fats and meats and to keep daily calorie intake under 1,800 a day for men and 1,500 for women.

The Mediterranean diet had the same overall calorie limits, but participants could eat fats, mainly olive oil and nuts, in moderation. These dieters also ate poultry and fish but little red meat.

The low-carbohydrate group ate an Atkins diet, in which they could consume all they wanted, provided very little of it was carbohydrates. Protein and fat intake weren't limited, but dietitians urged participants to choose vegetarian foods when available. All groups avoided trans fats.

Because the study participants ate lunch at the same cafeteria, they obtained food that fit their diets for the midday meal, the largest of the day.

After two years, low-carb dieters had lost an average of 5.5 kilograms, compared with the 3.3 kilograms lost by the low-fat dieters. Mediterranean dieters showed results between the two.

Low-carb dieters also increased their average HDL cholesterol, the good kind, by 8.4 points--2 points more than the others. LDL, the bad cholesterol, didn't change significantly in any group. Also, the low-carb and Mediterranean dieters lowered blood levels of triglycerides (fats) significantly more than the low-fat group.

Other studies have tackled the low-fat versus low-carb issue, with mixed results. Some found that low-carb diets induced quick weight loss but that early gains faded after six months.

This study and previous reports "are showing repeatedly that higher-fat diets do not worsen the overall blood cholesterol profile," says internist William Yancy Jr. of Duke University in Durham, N.C.

The Atkins Foundation provided partial support for the study.

Average kg lost per person

Leaving the bread behind

Low-fat diet         3.3 kg (7.3 lbs)
Mediterranean diet   4.6 kg (10.1 lbs)
Low-card diet        5.5 kg (12.1 lbs)

Data from 272 people show that on average
low-carb dieters lost more weight than low-fat
dieters after two years.

Note: Table made from bar graph.