Low-Carbohydrate Diet

Low-carbohydrate diets, such as the "Atkins" and "South Beach" diets, are currently popular ways to lose weight. Such diet plans involve restricting the type and amount of carbohydrate eaten.

One of the earliest descriptions of a low-carbohydrate diet was by William Banting in the 1860s in England. At the age of 66, Banting found success in following a carbohydrate-restricted diet: in the course of one year, he lost 46 pounds of his initial weight of 202 pounds. His impression was that "any starchy or saccharine matter tends to the disease of corpulence in advanced life". He claimed he was never hungry and that "the great charms and comfort of the system are that its effects are palpable within a week of trial and creates a natural stimulus to persevere for a few weeks more".

In a recent small trial, 63 obese men and women were assigned to either a low-carbohydrate diet or a low-fat diet (1). People on both diets lost weight. The carbohydrate-restricted group initially lost weight at a faster rate, but when reviewed at the end of the year there was no significant difference in weight loss between the two groups (1). It was found that low-carbohydrate dieters (who were allowed unrestricted amounts of protein and fat) actually had a lower energy intake than the low-fat diets (who were limited in their calorie intake). It may be that when carbohydrates are restricted, weight loss is due to a lower calorie intake due to the monotony of the diet. It is also possible that the lower calorie intake may be because of a change in peripheral or central saiety signals, leaving people feeling more full after a meal.

A second study compared the effects of a carbohydrate-restricted diet on the risk of developing atherosclerosis (2). 132 severely obese men and women were assigned to either a low-carbohydrate or low-fat diet. Again, after a 6-month period both groups lost weight. They became more sensitive to insulin, and their triglyceride (TG) levels, a type of fat that is a risk factor for atherosclerosis, improved. However, the carbohydrate-restricted group lost more weight and showed a greater improvement in insulin sensitivity and TG levels. After one year, the weight loss between the two groups was similar, but the cardiogenic risk factors were improved in the low-carbohydrate dieters, TG levels were lower, and levels of HDL cholesterol, a type of fat that protects against atherosclerosis, were higher (3). Also, long-term sugar control, which can be measured by checking for the amount of glycosylated hemoglobin (HbA1c), was better in people on the low-carbohydrate diet. However, it remains unclear whether these beneficial effects would continue after 1 year.

At present, the risks of obesity are well known, and the benefits of weight loss by traditional low-calorie, low-fat, and high-complex carbohydrate diets are also well documented. Future research will clarify the long-term outcomes of a low-carbohydrate diet for achieving and maintaing a healthy weight together with the effects on the heart and other systems of the body.

References
1. Foster GD, Wyatt HR, Hill JO, McGuckin BG, Brill C, Mohammed BS, Szapary PO, Rader DJ, Edman JS, Klein S. A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med 2003; 348:2082-2090. (PubMed)

2. Samaha FF, Iqbal N, Seshadri P, Chicano KL, Daily DA, McGrory J, Williams T, Williams M, Gracely EJ, Stern L. A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med 2003; 348:2074-2081. (PubMed)

3. Stern L, Iqbal N, Prakash Seshadri, Chicano KL, Daily DA, McGrory J, Williams T, Williams M, Gracely EJ, Samaha FF. The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomized trial. Ann Intern Med 2004; 140:778-785. (PubMed)

Source: National Library of Medicine