Low-Carb and Mediterranean Diets May Equal Watching Fat Intake
By Crystal Phend
BEER-SHEVA, Israel, 17july 2008--
Weight loss with both a low-carbohydrate and a Mediterranean diet may have advantages over a low-fat diet, researchers found.
The mean weight loss was greater with the low-carb diet (4.7 kg) and a Mediterranean diet (4.4 kg) than with the low-fat diet (2.9 kg, P<0.001 for interaction), reported Iris Shai, R.D., Ph.D., of Ben-Gurion University of the Negev here, and colleagues in the July 17 issue of the New England Journal of Medicine.
In the two-year randomized trial, the low-carb diet was the clear winner in lowering lipids with a 20% relative reduction in total-to-HDL cholesterol compared with 12% in the low-fat group (P=0.01).
Among diabetic patients, the Mediterranean diet held the greatest benefits for fasting plasma glucose compared with the low-fat diet (P<0.001 for interaction).
"In addition to producing weight loss in this moderately obese group of participants, the low-carbohydrate and Mediterranean diets had some beneficial metabolic effects," they wrote, "a result suggesting that … diets might be individualized according to personal preferences and metabolic needs."
For example, patients who find it difficult to cut calories might do best on a low-carb diet, which achieved a similar caloric deficit as the other diets in the study without restricting calories directly, they said.
Their Dietary Intervention Randomized Controlled Trial (DIRECT) included 322 moderately obese adults (mean BMI 31 kg/m2) at an isolated workplace in Israel with an on-site medical clinic and a cafeteria that provided lunch in accordance with diet groups.
Participants were mostly middle age men (86%, average age 52).
Registered dietitians met with patients in groups several times over the first two months and at six-week intervals thereafter, for a total of 18 90-minute sessions.
The low-fat, low-calorie diet based on American Heart Association guidelines aimed at 1,500 to 1,800 kcal a day with 30% of calories from fat, 10% of calories from saturated fat, and an intake of 300 mg of cholesterol per day.
The Mediterranean diet emphasized vegetable, poultry, and fish intake with daily calories restricted to 1,500 to 1,800 kcal and olive oil and nuts as the main sources of added fat.
The low-carbohydrate diet was based on the Atkins diet and did not limit calorie, protein, or fat intake, although vegetarian sources of fat and protein were suggested.
Adherence to these diets was high, with an average of 95.4% at 12 months and 84.6% at 24 months, whereas most diet trials have high dropout rates of 15% to 50% within the first year.
Dieters in all three groups significantly reduced daily energy intake (P<0.001) and increased physical activity compared with baseline without differences between groups.
Weight loss peaked at six months followed by partial rebound and then a plateau during the maintenance phase from seven to 24 months.
Overall at 24 months, the average weight loss compared with baseline was:
-2.9 kg for the low-fat group
-4.4 kg for the Mediterranean diet group
-4.7 kg for the low-carbohydrate group
Weight changes were even greater among the 272 participants who stuck with the diet for the full 24 months (-3.3, -4.6, and -5.5 kg in the diet groups, respectively, P=0.03 low-fat versus low-carb).
Although relatively few in number, the 45 women participants tended to lose more weight on the Mediterranean diet than on the other diets over 24 months (-6.2 kg versus -0.1 on low-fat and -2.4 kg on low-carb diets, P<0.001 for interaction).
"This possible sex-specific difference should be explored in further studies," the researchers said.
Whereas no effects were seen on LDL cholesterol, HDL cholesterol increased in all groups, particularly the low-carbohydrate versus the low-fat group (8.4 versus 6.3 mg/dl, P<0.01 for interaction).
Those on the low-carb diet likewise showed the most improvements in triglyceride levels compared with the low-fat diet (23.7 versus 2.7 mg/dl, P=0.03 for interaction).
The Mediterranean diet, though, came out ahead on most glucose control measures.
Among the 36 participants with diabetes, fasting plasma glucose fell only in the Mediterranean-diet group (32.8 mg/dl, P<0.001 versus low-fat diet).
Insulin resistance decreased as measured by HOMA-IR at 24 months with the Mediterranean diet compared with the low-fat diet (2.3 versus 0.3, P=0.02), although the authors acknowledged that HOMA-IR is not an optimal test.
Glycosylated hemoglobin decreased most with the low-carb diet (0.9% versus 0.4% low-fat and 0.5% Mediterranean diet, P<0.05 for low-carb).
The study was limited by the high proportion of male subjects and its setting in a restricted workplace. Although the workplace-based intervention may make it difficult to generalize the results to other populations, the researchers said they believed "similar strategies to maintain adherence could be applied elsewhere."
The study was supported by the Nuclear Research Center Negev, the Dr. Robert C. and Veronica Atkins Research Foundation, and the S. Daniel Abraham International Center for Health and Nutrition of Ben-Gurion University. The researchers reported no potential conflict of interest.
Weight loss with both a low-carbohydrate and a Mediterranean diet may have advantages over a low-fat diet, researchers found.
The mean weight loss was greater with the low-carb diet (4.7 kg) and a Mediterranean diet (4.4 kg) than with the low-fat diet (2.9 kg, P<0.001 for interaction), reported Iris Shai, R.D., Ph.D., of Ben-Gurion University of the Negev here, and colleagues in the July 17 issue of the New England Journal of Medicine.
In the two-year randomized trial, the low-carb diet was the clear winner in lowering lipids with a 20% relative reduction in total-to-HDL cholesterol compared with 12% in the low-fat group (P=0.01).
Among diabetic patients, the Mediterranean diet held the greatest benefits for fasting plasma glucose compared with the low-fat diet (P<0.001 for interaction).
"In addition to producing weight loss in this moderately obese group of participants, the low-carbohydrate and Mediterranean diets had some beneficial metabolic effects," they wrote, "a result suggesting that … diets might be individualized according to personal preferences and metabolic needs."
For example, patients who find it difficult to cut calories might do best on a low-carb diet, which achieved a similar caloric deficit as the other diets in the study without restricting calories directly, they said.
Their Dietary Intervention Randomized Controlled Trial (DIRECT) included 322 moderately obese adults (mean BMI 31 kg/m2) at an isolated workplace in Israel with an on-site medical clinic and a cafeteria that provided lunch in accordance with diet groups.
Participants were mostly middle age men (86%, average age 52).
Registered dietitians met with patients in groups several times over the first two months and at six-week intervals thereafter, for a total of 18 90-minute sessions.
The low-fat, low-calorie diet based on American Heart Association guidelines aimed at 1,500 to 1,800 kcal a day with 30% of calories from fat, 10% of calories from saturated fat, and an intake of 300 mg of cholesterol per day.
The Mediterranean diet emphasized vegetable, poultry, and fish intake with daily calories restricted to 1,500 to 1,800 kcal and olive oil and nuts as the main sources of added fat.
The low-carbohydrate diet was based on the Atkins diet and did not limit calorie, protein, or fat intake, although vegetarian sources of fat and protein were suggested.
Adherence to these diets was high, with an average of 95.4% at 12 months and 84.6% at 24 months, whereas most diet trials have high dropout rates of 15% to 50% within the first year.
Dieters in all three groups significantly reduced daily energy intake (P<0.001) and increased physical activity compared with baseline without differences between groups.
Weight loss peaked at six months followed by partial rebound and then a plateau during the maintenance phase from seven to 24 months.
Overall at 24 months, the average weight loss compared with baseline was:
-2.9 kg for the low-fat group
-4.4 kg for the Mediterranean diet group
-4.7 kg for the low-carbohydrate group
Weight changes were even greater among the 272 participants who stuck with the diet for the full 24 months (-3.3, -4.6, and -5.5 kg in the diet groups, respectively, P=0.03 low-fat versus low-carb).
Although relatively few in number, the 45 women participants tended to lose more weight on the Mediterranean diet than on the other diets over 24 months (-6.2 kg versus -0.1 on low-fat and -2.4 kg on low-carb diets, P<0.001 for interaction).
"This possible sex-specific difference should be explored in further studies," the researchers said.
Whereas no effects were seen on LDL cholesterol, HDL cholesterol increased in all groups, particularly the low-carbohydrate versus the low-fat group (8.4 versus 6.3 mg/dl, P<0.01 for interaction).
Those on the low-carb diet likewise showed the most improvements in triglyceride levels compared with the low-fat diet (23.7 versus 2.7 mg/dl, P=0.03 for interaction).
The Mediterranean diet, though, came out ahead on most glucose control measures.
Among the 36 participants with diabetes, fasting plasma glucose fell only in the Mediterranean-diet group (32.8 mg/dl, P<0.001 versus low-fat diet).
Insulin resistance decreased as measured by HOMA-IR at 24 months with the Mediterranean diet compared with the low-fat diet (2.3 versus 0.3, P=0.02), although the authors acknowledged that HOMA-IR is not an optimal test.
Glycosylated hemoglobin decreased most with the low-carb diet (0.9% versus 0.4% low-fat and 0.5% Mediterranean diet, P<0.05 for low-carb).
The study was limited by the high proportion of male subjects and its setting in a restricted workplace. Although the workplace-based intervention may make it difficult to generalize the results to other populations, the researchers said they believed "similar strategies to maintain adherence could be applied elsewhere."
The study was supported by the Nuclear Research Center Negev, the Dr. Robert C. and Veronica Atkins Research Foundation, and the S. Daniel Abraham International Center for Health and Nutrition of Ben-Gurion University. The researchers reported no potential conflict of interest.
Primary source: New England Journal of MedicineSource reference:Shai I, et al "Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet" N Engl J Med 2008; 359: 229-41.
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