The Durk Pearson & Sandy Shaw^®
Life Extension News^TM
Volume 10 No. 1 • March 2007

We have long considered a modification of dietary carbohydrates [decreasing easily digestible carbohydrates—which are rapidly broken down into glucose—while increasing indigestible carbohydrates (fiber)] to be a cornerstone of a healthy diet. For example, see Chapter 8 of our 1986 book The Life Extension Weight Loss Program (Doubleday). Our recent discovery of the availability of a very-high-soluble-fiber (15% beta-glucans) and insoluble-fiber (15%), reduced-digestible-carbohydrates (about 30% resistant starch) whole grain (a strain of barley with about three times the soluble fiber content of whole oats) has resulted in a transformation of our diet. We are now ingesting far more soluble fiber than we ever have before, and, by combining the barley with other foods, we have reduced the glycemic index of our general diet. There are a rapidly increasing number of papers being published on the benefits of a restricted-carbohydrate diet, a few of which are described below.

Restricting dietary carbohydrates promotes better health whether or not there is weight loss

A recent review¹ reported on the effects of restricting dietary carbohydrates, with and without weight loss, on measures of atherogenic dyslipidemia (such as high triglycerides or LDL-cholesterol). The minireview summary¹ of the results of restricting carbohydrates included the following:

1. Carbohydrate restriction has been shown to have beneficial effects on fasting and postprandial (after-meal) triacylglycerol (fats), HDL-cholesterol, apolipoproteins, and lipoprotein subclasses. Higher triacylglycerol levels are associated with insulin resistance and also increase the production and secretion of atherogenic VLDL (very-low-density lipoproteins) from the liver. The review’s author reports that, according to a meta-analysis, plasma triacylglycerol can be expected to decrease by 0.015 mmol/L per kilogram of weight loss. A separate paper found that, although weight loss from a diet restricted in fat (<30% of kilocalories from fat) was similar to that from a diet restricted in carbohydrates (<30 g of carbohydrate/day), the improvements in plasma triacylglycerol levels were significantly greater in the group on the restricted-carbohydrate diet. After one year, the weight lost in the low-fat group was 3.1 ± 8.4 kg, and that lost in the restricted-carbohydrate group was 5.1 ± 8.7 kg. The expected reduction in triacylglycerol for the low-fat group was 0.047 mmol/L, while the actual reduction was 0.05 ± 0.96 mmol/L, in close agreement. By contrast, the expected reduction in triacylglycerol for the restricted-carbohydrate group was 0.077 mmol/L, yet the actual reduction was 0.65 ± 1.78 mmol/L, greater than 8 times the expected reduction. And this occurred despite the fact that the actual consumption of carbohydrate by participants was 120 g/day, 4 times as great as the amount they were supposed to consume.

Furthermore, the review continues, even in the absence of weight loss, studies have shown that consuming a diet restricted in carbohydrates can reduce plasma triacylglycerol. One study was reported to have found a greater reduction in plasma triacylglycerol during the weight-stable (maintenance) phase for the 26% carbohydrate group compared with the 54% carbohydrate group. Other studies were reported with similar findings in normal-weight healthy men and women and in type 2 diabetics.

2. Another consistent result of restricting dietary carbohydrates is an increase in HDL-C (HDL-cholesterol).² In addition to increasing protective HDL-C levels, the author reports that, in a study of a restricted-carbohydrate diet he published with coworkers, they observed a significant increase in large HDL particles, with a reduction of medium HDL particles and no change in the quantity of small HDL particles. Large HDL particles are advantageous because they have a longer plasma half-life. The author and his coworkers believe that the results of this study (which found increased peripheral cholesterol removal and esterification and a reduced incorporation of triacylglycerol into HDL particles) support the idea that reducing carbohydrates increases HDL, not by inducing additional HDL synthesis but by increasing the plasma half-life of HDL particles. The author also cites papers in which increased HDL-C has been reported in normal-weight men and women who followed a weight-maintenance diet restricted in carbohydrates.

References

1. Wood RJ. Effect of dietary carbohydrate restriction with and without weight loss on atherogenic dyslipidemia. Nutr Rev 64(12):539-45 (2006).
2. Volek and Feinman. Carbohydrate restriction improves the features of metabolic syndrome. Metabolic syndrome may be defined by the response in carbohydrate restriction. Nutr Metab (Lond) 2:31 (2005).