Low-Carb, Low-Fat Diets Get Similar Results

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By Jeanie Lerche Davis:

Are you cutting carbs to lose weight? You're on the right path -- as long as you stick to it.


Two studies, published this week in the Annals of Internal Medicine, provide much-needed scientific evidence about low-carb diets and provide interesting insights into what types of diets work --and why.


"We can no longer dismiss the very low-carbohydrate diets," writes Walter C. Willett, MD, DrPH, with Harvard School of Public Health, in an accompanying editorial. "Dr. Atkins deserves credit for his observations that many persons can control their weight by greatly reducing carbohydrate intake."


Indeed, low-carb plans -- like the popular Atkins and South Beach diets -- have gained great popularity over recent years. Yet there is "a paucity of scientific evidence on their effectiveness," writes researcher William S. Yancy, Jr., MD, MHS, who is a professor of Medicine at Duke University Medical Center.


Yancy's six-month study pits a low-fat diet against a low-carb program -- finding that low-carb indeed works.


But the story doesn't end there. It seems that six months into a low-carb program, the dramatic weight loss ends abruptly. That's what researcher Frederick F. Samaha, MD, found in his year-long study of low-carb vs. low-fat diets. In fact, the low-carb and low-fat groups ended up getting similar weight-loss results.


The voice of reason from one nutritionist: Cutting back on food is what works. "There are many different paths to weight loss," says Sheah Rarback, RD, MS, RD/LD, of the University of Miami School of Medicine and spokeswoman for the American Dietetic Association.


"Whether you choose the low-fat or low-carb path, you must find a plan that works for you -- one that you can stick with, and that includes healthy foods," she tells WebMD. "Cutting back on sugar, refined flour, and white flour, that's what's important."


The details on the two studies:


Low-Carb vs. Low-Fat: A Six-Month Study


In his study -- funded by the Robert C. Atkins Foundation -- Yancy enrolled 120 overweight adults, all of whom had high cholesterol:


One-half followed a low-carb diet -- restricting intake to less than 20 grams of carbs daily.
The other half had a low-fat diet -- total fat less than 30% of calories, saturated fat less than 10% of calories, cholesterol intake less than 300 milligrams -- plus cutting calorie intake by 500 to 1,000 calories.
All were advised to exercise three times weekly, drink lots of water, and keep a "food diary" tracking their eating pattern.

At the end of six months: "People lost more weight -- an average of 26 pounds -- on the low-carb diet, compared with 14 pounds on the low-fat diet," William S. Yancy, Jr., MD, MHS, professor of medicine at Duke University Medical Center, tells WebMD. "That's a pretty dramatic weight loss in six months."


He also found:


The low-carb group had a 13% weight loss compared with 7% in the low-fat group.
The low-carb group lost 6% body fat compared with 5% in the low-fat group.
The low-carb group had better triglycerides and HDL "good" cholesterol levels.
Both groups had only small changes in LDL "bad" cholesterol.

Weight loss in both groups resulted mostly from cutting calories -- even though the diets were quite different, writes Yancy. The biggest concern about a low-carb diet, which is usually higher in animal fats and cheeses, is whether LDL "bad" cholesterol will get worse. However, that did not happen overall in this study, he reports.


Also, fewer people dropped out of the low-carb group, he notes. "A lot of people say it's hard to stick to the low-carb diet. But it's hard for people to stick to any diet," Yancy tells WebMD. "With all the low-carb products coming out -- and with restaurants making changes, too -- it should be easier for people to stay on a low-carb diet."


However, those low-carb products are "a double edged sword," he admits. "If people end up eating more calories during the day, they won't lose weight. It's an important part of the formula -- cutting back on calories."


Low-Carb vs. Conventional Diet: A One-Year Study


Samaha's one-year study is the largest and longest to date looking at low-carb diets, he writes.


In a previous study, his group of researchers showed that severely obese people following a low-carb diet for six months lost more weight -- and had greater improvements in triglyceride, blood sugar, and insulin levels -- than volunteers following a conventional low-calorie, low-fat diet. Samaha is a researcher with the Philadelphia Veterans Affairs Medical Center.


His current study builds on that research -- showing weight-loss results over the long-term.


The volunteers were 132 severely overweight patients; 83% had diabetes or were pre-diabetic (had borderline high blood sugar levels). They were assigned to follow either a low-carb (less than 30 grams per day) or a conventional calorie-cutting diet (cutting calories by 500 a day, with less than 30% of calories from fat).


At the end of one year:


The low-carb group had a dramatic weight loss in six months and was able to maintain most of that weight loss over the course of the year.
The low-fat group had a slower, steadier weight loss that continued through the year.
Both groups had similar amount of total weight loss -- 11 pounds to 19 pounds in the low-carb and 7 pounds to 19 pounds in the low-fat group.

Also:


Both groups had similar total and LDL cholesterol levels.
The low-carb group had improved triglycerides.
The conventional group had worse HDL levels.

Bottom line: The low-carb group had a direct improvement in triglyceride, HDL cholesterol, and blood sugar control in the volunteers with diabetes, he writes.


His study is limited, he notes, by the high numbers of people who dropped out. Also, most people did not stick closely to the diets.


"People who have problems with triglycerides, HDL, and blood sugar control are probably overeating carbohydrates," Samaha tells WebMD. "Cut carbs, and you'll see improvements."

SOURCES: Yancy, W.Annals of Internal Medicine, May 18, 2004: vol 140: pp 769-777. Stern, L. Annals of Internal Medicine, May 18, 2004; vol 140: pp 778-786. Willett, W. Annals of Internal Medicine, May 18, 2004; vol 140: pp 836-837. William S. Yancy, Jr., MD, MHS, professor of medicine, Duke University Medical Center. Frederick Samaha, MD, Philadelphia Veterans Affairs Medical Center. Sheah Rarback, RD, MS, RD/LD, University of Miami School of Medicine; spokeswoman, American Dietetic Association.