A carbohydrate-restricted diet may be more effective than one emphasizing reduced fat intake in modestly improving triglyceride and HDL (good)cholesterol levels, according to reports in the Annals of Internal Medicine. This finding counters the concern that the increased fat intake of such diets could adversely affect lipid levels.
However, results vary widely regardless of which approach dieters take, say researchers, so physicians should counsel patients to adopt a diet they can stick to, rather than one emphasizing rapid weight loss.
In a trial at Duke University Medical Centre in Durham, North Carolina, scientists randomly assigned 60 obese but otherwise healthy individuals with high lipid levels to a conventional diet that reduced caloric intake by 500 to 1000 calories per day, with less than 30 percent of calories from fat. The other 60 subjects were assigned to a diet of less than 20 grams of carbohydrate daily plus nutritional supplements.
The 45 subjects in the low-carb group who completed the 6-month study lost an average of 12.9 percent of their body weight. In the low-fat group, 34 completed the study, and their weight loss averaged 6.7 percent.
The average level of LDL (bad) cholesterol decreased more with restricted carbohydrates. However, 13 of 44 (30 percent) had 10 percent or higher increases in LDL, compared with 5 of 31 (16 percent) among those on the conventional weight-reduction diet. HDL cholesterol, the "good" cholesterol, increased more in the low-carb group.
In the other study, researchers from Philadelphia Veterans Affairs Medical Centre enrolled 132 severely obese subjects, among whom 64 were placed on a diet with carbohydrate restriction and 68 on a conventional diet.
After 1 year, 20 in the low-carb group and 25 in the low-fat group had dropped out. Those in the low-carb group lost weight faster, but by study end, weight loss did not differ significantly between the two groups.
Triglyceride levels decreased more in the low-carb group in the Philadelphia trial, and HDL cholesterol levels decreased less. Among the 54 subjects with diabetes, glucose levels declined significantly more in the low-carb group.
In both studies, overall caloric intake decreased more in the low-carbohydrate diet, but the difference was not statistically significant.
A leading nutrition researcher said in the accompanying editorial encouraged people to experiment with various methods for weight control, including reduced carbohydrate diets, as long as they emphasize healthy sources of fat and protein and incorporate regular physical activity.
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