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Do they really work?
An analysis of carbohydrate condemnation
November 11, 2008
Nowadays, many people associate the concept of low-carbohydrate diets with Dr. Robert Atkins, the man who made this type of weight modification popular during the late 1990s (Goodwin, 2006). Although he referred to it as a “New Diet Revolution,” the concept of low-carb dieting had been around for almost 100 years by the time Atkins published his first book about it in the 1970s. In 1863, Englishmen William Banter wrote a booklet entitled Letter on Corpulence, Addressed to the Public, in which he claimed that, by cutting carbohydrates out of his diet, he lost over 21 kg “without feeling any hunger” (Astrup, 2004). Banter’s ideas about dieting and carbohydrates never seemed to catch on until the late 20th century, when news of an obesity epidemic made weight-loss seem more necessary than ever. Almost overnight, low-carb diets such as the Atkins’ diet, the South Beach diet, and the Zone diet came to the rescue, armed with William Banter’s belief that starche and/or saccharine is bad for the body (Mobbs, 2006).
Conventional weight-loss plans tend to focus on decreasing the amount of calories and fats consumed on a regular basis in addition to regular exercise Foster, 2003). Why, then, do so many people swear by diets that only affect carbohydrate consumption? According to Dr. Atkins, “When you eat too many carbohydrates (carbs), your body burns some of those carbs for energy and stores the excess carbs as fat” (http://atkinscenter.com/). Thus, a diet solely consisting of meat, vegetables, and the occasional fruit should reduce the amount of unnecessary fat in the body without exercising or calorie counting (Goodwin, 2006). Sounds pretty nice, huh? In fact, it sounds too good to be true.
Effectiveness of Low-carb diets
Empirical studies that compare the effects of low-carbohydrate diets with their low-calorie counterparts have shown that there are both negative and positive effects of following Atkins' "miracle diet."
Good News: Cost-effectiveness of Low-Carb Diets
A study that followed participants for 1 year found no significant weight loss differences between people in low-carb diets and people in low-calorie or low-fat diets. Additionally, subjects in the low-carb condition were more likely to stick to the diet and less likely to leave the experiment before the end of the year. In order to assess the cost-effectiveness of each diet, researchers solved for a cost-effectiveness ratio (CER) by dividing the amount of wages lost (when participants had to miss work to see a nutritionist) by the difference in Quality Adjusted Life Years (QALYs) from the beginning to the end of the study. At the end of the year, low-carb diets were no less cost-effective than standard diets (Tsai, 2005).
Unfortunately, an analysis of this study is limited because the participants were atypical. In other words, a disproportionate amount were men and came from lower socieconomic status than most individuals who are obese (Tsai, 2005).
Bad News: Low-Carb Diets and Coronary Disease
The first study to examine both short- and long-term weight changes in a group of low-carb dieters was done in 2006. At first, the study seemed to support the use of low-carb diets, due to the fact that people in both the low-carb condition and the traditional diet condition showed no significant differences in terms of weight loss. In other words, low-carb diets seemed to be just as effective as the standard low-calorie diet. This is particularly surprising, given the fact that, at 1-, 2-, and 3-year follow-ups, low-carb dieters reported a higher saturated, monounsaturated, and polyunsaturated fat intake than those in the control. While they lost almost the same amount of weight as people on a high-carb, low-calorie diet, the amount of saturated fats they consumed put them at greater risk for coronary disease. By the end of the study, low-carb dieters regained the weight they lost much faster (Phelan, 2007).
There were limitations to this particular study. First of all, the research groups were not formed using random assignment. Because all participants were on the National Weight Control Registry, they were already considered successful at weight loss even before joining the study. In addition, many of the variables in question (e.g., weight, food intake, etc.) were measured using self-reports (Phelan, 2007).
Good News: HDL Cholesterol and Low-carb Diets
Another year-long study comparing low-carb diets with low-fat diets found that, while the amount of weight lost at the end of the month was the same for individuals in both conditions, the rate of loss differed drastically in the first three to six months. Specifically, low-carb exhibited significant loss at three months and at six months, but by the twelve month mark, members of both groups were practically equal in terms of total weight lost over the year. Another interesting point that is the fact that LDL cholesterol levels the blood stream increased and decreased in a pattern opposite that of weight loss.
This study was well done in that the participants were randomly assigned to each of the conditions and blood tests (instead of self-reports) were used to evaluate how much a subject adhered to their specified diet (Foster, 2003).
Low-carb diets are no better than traditionally established weight loss plans that encourage calorie/cholesterol/fat restriction.
Astrup, A., Larsen, T., & Harper, A. (2004). Atkins and other low-carbohydrate diets: hoax or an effective tool for weight loss?. The Lancet, 364(9437), 897-899. Retrieved Oct. 7, 2008, from the ScienceDirect database.
Atkins Nutritional. (n.d.). Retrieved Oct. 8, 2008, from http://atkinscenter.com.
Bray, G. (2003). Low-Carbohydrate Diets and Realities of Weight Loss. Journal of the American Medical Association, 289(14), 1853-1855. Retrieved Oct. 8, 2008, from the PubMed database.
Dolson, L. (n.d.). Getting Started on a Low-Carb Diet - Everything You Need to Know About Low-Carb Diets. Retrieved Oct. 8, 2008, from http://lowcarbdiets.about.com/od/lowcarb101/u/gettingstarted.htm.
Foster, G., Wyatt, H., Hill, J., Mcguckin, B., Brill, C., Mohammed, B., Szapary, P., Rader, D., Edman, J., & Klein, S. (2003). A Randomized Trial of a Low-Carbohydrate Diet for Obesity. The New England Journal of Medicine, 348(21), 2082-2089. Retrieved Oct. 7, 2008, from the Google Scholar database.
Goodwin, K. (2006, Oct. 24). Atkins Diet: A Comprehensive Analysis | The Diet Channel. Retrieved Oct. 8, 2008, from http://thedietchannel.com/atkins.htm.
Mobbs, C., Mastaitis, J., Yen, K., Schwartz, J., Mohan, V., Poplawski, M., & Isoda, F. (2007). Low-carbohydrate diets cause obesity, low-carbohydrates reverse obesity: A metabolic mechanism resolving the paradox. Appetite, 48, 135-138. Retrieved Oct. 8, 2008, from the ScienceDirect database.
Phelan, S., Wyatt, H., Nassery, S., Dibello, J., Fava, J., Hills, J., & Wing, R. (2007). Three-Year Weight Change in Successful Weight Losers who Lost Weight on a Low-Carbohydrate Diet. Obesity Research, 15(10), 2470-2477. Retrieved Oct. 8, 2008, from the PsychINFO database.
Tsai, A.G., Glick, H.A., Shera, D., Stern, L., & Samaha, F.F. (2005). Cost-Effectiveness of a Low-Carbohydrate Diet and a Standard Diet in Severe Obesity. Obesity Research, 13(10), 1834-1840. Retrieved Oct. 8, 2008, from the The Obesity Society database.
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