The study investigated 44 overweight men and women with hyperlipidemia who were randomized to the low-carb "eco-Atkins" diet or to a lacto-ovo vegetarian version of the DASH diet.
While individuals in both groups lost a "fairly dramatic" 4 kg, those following the "eco-Atkins" diet had a greater decrease in LDL-C, lead author Dr David JA Jenkins (University of Toronto, ON) told heartwire .
The study message is:"Use more plant foods to lower LDL-C--whether it is oils, proteins, carbohydrates, or fiber," said Jenkins.
"We conclude that low-carbohydrate diets emphasizing vegetable sources of protein, such as gluten, soy, and nuts, together with vegetable oils, can be used in weight-reduction diets to improve serum lipid concentrations," the researchers write.
The study is published in the June 8, 2009 issue of the Archives of Internal Medicine.
Dietary Dilemma
Choosing the optimal proportion of fat, protein, and carbohydrate for weight loss plus cholesterol-lowering can be a dilemma, the authors write.
A low-carb, high-meat diet--such as the Atkins diet--can induce weight loss, lower triglycerides, and raise HDL-C levels, but it also tends to increase LDL-C levels. On the other hand, a high-carb, low-animal-product diet lowers CHD risk factors.
To determine weight loss and the effect on serum lipid concentrations from a low-carb diet where plant sources replace animal-based proteins and fats, the researchers compared the "eco-Atkins" diet with a control diet.
The "eco-Atkins" diet replaces meat, eggs, and butter with plant-based nutrients, which makes it more ecologically friendly in terms of the use of land resources and the cost of agriculture, said Jenkins.
This test diet provided the minimum level of carbs recommended by the National Academy of Sciences Institute of Medicine--130 g/day--by eliminating starch-based bread, rice, and potatoes but including high-fiber oat-bran cereal and vegetables such as okra and eggplant. Protein sources included nut bread and tofu. Fats included olive oil, nuts, and avocados.
The researchers compared this with a positive control diet that would be expected to benefit heart health, said Jenkins. The control diet extended the DASH diet in that it allowed low-fat dairy products, egg substitutes, and whole-grain products but eliminated rather than reduced meat consumption.
The researchers studied 44 overweight men and women with hyperlipidemia.
The subjects were randomized to the test diet--27% carbohydrates, 30% protein, and 43% fat--or control diet--58% carbohydrates, 17% protein, and 25% fat.
All diets were designed to provide 60% of estimated calorie requirements. Prepared diet foods were shipped to the subjects.
Weight loss was similar in both groups. However, those in the low-carb, plant-based diet group had greater reductions in LDL-C levels and in the ratio of total cholesterol to HDL-C. They also had more beneficial changes in apolipoprotein levels and small but significantly greater changes in blood pressure.
Too Soon to Recommend "Eco-Atkins" Diet
In an accompanying editorial [2], Drs Katherine R Tuttle and Joan E Milton (University of Washington School of Medicine, Spokane) note that while the study provides insight into diet design, individuals in both groups lost weight due to caloric reduction.
"It is premature to recommend the 'eco-Atkins' diet as a weight-loss diet of choice without confirmation of its efficacy in larger studies of more diverse and higher–risk individuals," they caution. "Long-term studies are also essential to ascertain both sustainability and safety. Finally, realistic strategies for implementation will require assessment in settings in which participants procure and prepare their own meals."
Can the Diet Be Maintained?
Commenting on the study for heartwire , Dr Robert H Eckel (University of Colorado School of Medicine, Denver) observed that although weight loss was similar with both diets, lipid levels were better with the test diet.
"But with the types of fat utilized in the 'eco-Atkins' diet, that's no surprise," he added. "There were very low concentrations of saturated fats and cholesterol, unlike in the Atkins diet, where during the first four weeks the saturated fat content is 24% of total calories."
It is certainly a better choice than the Atkins diet for individuals who want to follow a low-carb diet, he added. However, like the Atkins diet, the "eco-Atkins" diet is restrictive. "The question is how long people can maintain this way of eating."
Ongoing Research
To answer questions about long-term results in people not provided with prepared diet foods, the research team is conducting an ongoing study that extends to seven months, said Jenkins. Preliminary, unpublished results show that while body-weight reduction is maintained, long-term differences in LDL cholesterol are not as dramatic.
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