Low-Carb Diets Beat Low-Fat for Weight Loss And Lipid Changes at 2 Years

The two-year study, which managed to keep almost 85% of the 322 study participants on one of the three diets for the entire period, offers the hope that weight-loss diets can be tailored to personal preferences, without sacrificing efficacy, researchers say.

Dr Iris Shai lead author on the study (Ben Gurion University of the Negev, Beer-Sheva, Israel) stated that, "Several recent one-year dietary studies have led the American Diabetes Association to state in January 2008 that low-carb diets should be considered for a maximum of one year."  "The current two-year study suggests that one low-fat diet doesn't fit all, meaning that the old paradigm should be reconsidered."

At the start of the study, DIRECT subjects were middle-aged (mean age 52 years) and mildly obese (body-mass index = 31). All participants were randomized to one of three diets: low-fat/restricted-calorie diet; Mediterranean/restricted-calorie diet; or low-carbohydrate diet, with no restriction on calories. After two years, adherence to their respective diets ranged from more than 90% in the low-fat group, to 85% in the Mediterranean diet group, to 78.0% in the low-carb group.
Weight loss occurred in all three groups over the 24 months but was greater in the Mediterranean and low-carb groups. In men — who made up the bulk of the study cohort — weight loss was greatest in the low-carb group, whereas women — just 45 in the study cohort — appeared to lose more weight on the Mediterranean diet. When the analysis was performed just in the 272 "completers" who adhered to the diet for the entire study period, the pattern of weight loss associated with each diet was similar.

Weight loss

Changes in lipid parameters were also most striking in the low-carb and Mediterranean-diet groups. High-density lipoprotein (HDL) increases and triglyceride decreases were most pronounced in the low-carb group, while reductions in low-density lipoprotein (LDL) cholesterol were greatest in the Mediterranean-diet group. Reductions in total cholesterol/HDL ratio were greatest in the low-carb group, closely followed by the Mediterranean-diet group.

Lipid changes

In the subset of patients with diabetes — just 36 out of 322 subjects — the Mediterranean diet appeared to improve fasting plasma glucose levels. According to Shai, the results suggest that "one size doesn't fit all."

"The current results suggest that Mediterranean and low-carbohydrate diets are effective alternatives to low-fat diets," she said. "The more favorable effects on lipids with the low-carbohydrate diet and on glycemic control with the Mediterranean diet suggest that personal preferences and metabolic considerations might inform individualized tailoring of dietary interventions."

One of the unique features of the study was its location: the DIRECT study was conducted at a nuclear research center in Israel with an on-site cafeteria and medical clinic. Participants in the trial ate their main meal of the day — lunch — in the workplace cafeteria, where food choices were carefully controlled and labeled. On-site dieticians worked regularly with participants to help them adhere to their diets. Indeed, the Nuclear Research Center Negev itself, along with the Robert C and Veronica Atkins Foundation — the low-carb diet in DIRECT was based on the Atkins diet — helped fund the study.
In the paper, Shai et al acknowledge that the setting was perfectly suited to a study of this kind, but that this doesn't mean these diets would not have worked elsewhere. "We took advantage of the isolated place, which is highly monitored by an excellent internal medical department, and a set of cafeterias [whose menus] we could modify. And in fact, she said, "we do believe that this optimal model could be applied in other workplaces, once the manager prioritizes this kind of long-term health-promotion project."

Low-carbohydrate diets have been compared with low-fat diets and thought to be feasible for weight loss, whereas a Mediterranean diet with moderate fat and high fiber and fish provides cardiovascular benefits, but common problems of weight-loss programs include high attrition rates and short duration.

This is a randomized trial conducted at a workplace with a medical clinic for 24 months in patients aged 40 to 65 years to compare the effect of the 3 diets on weight loss and metabolic changes.

Practice Pearls:

• Use of a low-fat, Mediterranean, and low-carbohydrate diet for 24 months is associated with weight loss in men and women.
• Use of a low-fat, Mediterranean, and low-carbohydrate diet for 24 months is associated with reduced waist circumference, improved lipid profile (best for low-carbohydrate diet), improved glycemic control (Mediterranean diet), and improved blood pressure.

Shai and colleagues publish the results of the Dietary Intervention Randomized Controlled Trial (DIRECT) in the July 17, 2008 issue of the New England Journal of Medicine LShai I, Schwarzfuchs D, Henkin Y, et al. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med. 2008;359:229-241.

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http://www.diabetesincontrol.com/issues/Issue 426/nejm.pdf

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DID YOU KNOW:  

Daily fruit juice linked to diabetes:: Fruit juice has been linked to a slight increase in type 2 diabetes in women, according to new research in the July 2008Diabetes Care. Three servings a day of fruit and leafy vegetables were not associated with the development of diabetes in the study. However, adding a single serving of fruit juice per day slightly increased the chances of developing the condition. The study was carried out over an 18-year period among more than 71,000 women. The authors of the study concluded that ‘caution should be observed in replacing some beverages with fruit juices in an effort to provide healthier options. The same caution applies to the recommendation that 100 per cent fruit juice be considered a serving of fruit’.

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