High-Carbohydrate Diets

Diets of high carbohydrate intake generally consists of 50 to 60 percent of total daily energy intake in carbohydrates, less than 30 percent fat, and less than 20 percent protein. Some common high-carbohydrate diets include the National Cholesterol Education Program (NCEP) Step I and Step II Diet with energy intake restriction; the Dietary Approaches to Stop Hypertension (DASH) diet, which is based on the U.S. Department of Agriculture Food Guide Pyramid; and some commercial programs such as Weight Watchers. The National Weight Loss Registry is one of the best places to go to find information on long-term successful weight-loss maintenance strategies. Over 5,000 people are registered because they have lost over 30 pounds and maintained for over a year. Recent results of the large prospective study reveal that the majority of people who are keeping it off are on high-carbohydrate, low-fat diets. Therefore, despite the Atkins craze of recent years, high-carbohydrate, low fat, and high-fiber diets are proven to be effective in terms of successful weight loss and maintenance, as well as improvements in cholesterol, thereby potentially reducing the risk of many major chronic illnesses, such as diabetes and certain types of cancer.

The general consensus for weight-loss recommendations would promote diets that are high in fiber, while some may say that these diets should also have a low glycemic index. The glycemic index, a concept introduced by D. J. Jenkins to classify foods containing carbohydrates, represents the blood glucose response (incremental area under the curve) to a food portion containing 50 grams of available carbohydrate compared with the response to an equivalent amount of either glucose or white bread.

A recent debate has arisen regarding the use of glycemic index/load for the control of diabetes, blood [Page 357]lipids, and weight control. In a review of clinical trials that compared the effects of high- and low-GI foods or diets on appetite, food intake, energy expenditure, and body weight, 15 out of 31 short-term studies found that low-GI foods were associated with greater satiety. On the contrary, reduced satiety or no differences were seen in 16 other studies. Further, reduced ad libitum food intake was associated with low-GI foods in seven studies, with opposite results in eight other studies. Whether reduced food intake translated to weight loss was explored in 20 studies of less than sux months in duration. However, 14 studies found no difference, whereas four studies showed weight loss achieved with a low-GI diet versus two studies on a high-GI diet. As reported by the comprehensive review, the average weight loss was 3.3 pounds on a low-GI diet and 3.5 pounds on a high-GI diet. With similar results, the evidence that low-GI diets are superior to high-GI diets with regards to weight loss is skim. Nonetheless, because each study varies slightly by design and execution, there have yet been long-term studies of low-GI versus high-GI diets where ad libitum intake and fluctuations in body weight are permitted.

High-carbohydrate diets have previously been criticized because unprocessed sugars cause hyperinsulinemia, which further leads to insulin resistance, obesity, and cardiovascular disease. Particularly, postprandial hyperglycemia has been found to increase the risk of cardiovascular disease and diabetes. However, if the unprocessed sugars are replaced with whole grains, then there would be many health benefits. High-fiber and low-glycemic index (GI) diets are associated with increased satiety, lower postprandial glycemic response, and lower insulin levels. A review of epidemiological studies looked at dietary glycemic load, whole grains, and systemic inflammation in patients with diabetes. Despite the current controversy surrounding the glycemic index, there is some evidence that suggest diets low in glycemic index/load or high in whole-grain products have been associated with decreased concentrations of inflammatory markers and increased adiponectin levels among diabetic patients. Such effects may be explained by the reduction in hyperglycemia-induced overproduction of oxidative stress and by the amelioration in insulin resistance, adiposity, dyslipidemia, and hypertension. Therefore, diets high in whole grains may have a protective effect against systemic inflammation in diabetic patients and may therefore be recommended to diabetic patients for the prevention of cardiovascular complications.

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