The First Health Blog Service

The Effects of Low Carb, High Protein Diets

February 27th, 2006

Obesity is a major health concern because of its effect on many chronic diseases. Strategies recommended for weight control have generally recommended the implementation of low fat dietary patterns, which facilitate energy restriction and cardiovascular disease risk reduction. However, there has also been an interest in the role of a high dietary ratio of protein to carbohydrate in enhancing weight loss and disease risk management.

Some studies have shown that a high ratio of protein to carbohydrate have positive effects on disease risk, including body composition, blood lipids, and glucose homeostasis, and that those benefits may be mediated somewhat by the effect of protein on satiety and by a lower glycemic load because of a lower carbohydrate intake. However, foods and dietary patterns high in protein may vary in saturated fat and concerns have been raised regarding the effect of high-protein (HP) diets on serum lipids and CVD risk. Therefore, a recent study published in the American Journal of Clinical Nutrition studied the effects of reduced caloric intake, associated with higher dietary protein from low saturated fat sources compared with a high-carbohydrate (HC) diet, on weight loss, body composition, CVD risk, nutritional status and markers of bone turnover in overweight and obese women.

One hundred women between the age of 20 years and 65 years of age and with a BMI between 27 and 40 were included in this study. The women were randomly assigned to 1 of 2 isocaloric dietary interventions for 12 weeks: 1) a high-protein, low saturated fat dietary pattern [HP group: 34% of calories from protein, 20% from fat (less than 10% from saturated fat)] and 2) a high-carbohydrate, low saturated fat dietary pattern [HC group: 17% of calories from protein, 20% from fat (less than 10% from saturated fat)]. Subjects were weighed every 14 days and DXA was performed at weeks 0 and 12. Fasting blood samples were collected at weeks 0, 4, 8, and 12 to test for lipids, insulin, and plasma glucose. Collection of total 24-hour urine output occurred at weeks 0 and 12.

Weight loss was 7.3 kg with both diets. Subjects with high serum triacylglycerol (greater than 1.5 mmol/L) lost more fat mass with the HP than with the HC diet. Triacylglycerol concentrations also decreased more with the HP than with the HC diet. Fasting LDL (by 6%) and HDL-cholesterol, glucose (by 4%), insulin, free fatty acid and C-reactive protein concentrations decreased with weight loss but there was no significant difference between the two diets. Serum vitamin B-12 increased 9% with the HP diet and decreased 13% with the HC diet. Folate and vitamin B-6 increased with both diets and homocysteine did not change significantly. Bone turnover markers increased 8% to 12% and calcium excretion decreased, while creatinine clearance decreased.

An energy-restricted diet high in protein from lean red meat and low fat dairy products seems to provide a weight loss advantage in subjects with elevated triacylglycerol levels, a marker of the metabolic syndrome. In addition, concerns that diets high in meat protein may have harmful effects on renal function and bone turnover were not substantiated by this study. Since this may be the first study to suggest a phenotype x diet interaction with respect to the magnitude of weight loss to different diet interventions, further confirmation is required in hypertriglyceridemic women.

By Many Noakes, Jennifer B. Keogh, Paul R. Foster, and Peter M. Clifton
COPYRIGHT 2005 Frost & Sullivan
COPYRIGHT 2005 Gale Group

Entry Filed under: Food