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Effectiveness of Diets for Weight Loss

En Español (Spanish Version)

The rising rates of obesity in the US create an urgent need to find the most effective diet plan. A proper plan will not only aid in weight management, but also decrease risks of diseases such as cancer or heart disease . However, there is a lot of conflict even in the medical community about which type of diet is best. Three of the most popular diets that have some degree of medical support include the low-fat diet, low-carbohydrate diet, and the Mediterranean diet .

Researchers in Israel, set out to evaluate the actual benefits of these three popular diets. The study, published in the New England Journal of Medicine , provided important insight into each diets' benefits. Participants in all three studies lost weight and experienced health benefits, but each diet had its unique strengths.

About the Study

The randomized, controlled study followed 322 moderately obese participants over two years. The participants were divided into three groups. Each group was assigned one of the following diet plans:

  • Low fat, restricted calories
  • Mediterranean, restricted calories
  • Low carbohydrate, no restricted calories

At the end of the two years:

  • The low-carbohydrate group lost the most weight (avg. 4.7 kg) (4.4 kg for Mediterranean group and 2.9 for low-fat group)
  • The low-carbohydrate group had the best improvement in cholesterol ratio
  • The Mediterranean diet group had the best improvements in fasting glucose levels

Not all participants completed the study. The highest rate of dropout was in the low-carbohydrate diet group (78% completed), followed by the Mediterranean diet group (85% completed), and the low-fat dieters (90% completed).

It may be important to note that although no conflict was reported, the study was supported in part by the Atkins Research Foundation. Atkins is a popular low-carbohydrate diet program.

How Does This Affect You?

There are many considerations when selecting the proper diet. Any existing health conditions need to be considered in your choices. This study suggests that the low-carbohydrate diet may be a better option if you have heart and or cholesterol concerns, whereas the Mediterranean diet may be better for people that need help with blood glucose control. In any case, diets that are too restricting are unlikely to be followed for extended periods of times.

Talk to a registered dietitian about diet options. A dietitian can take your health concerns and personal preferences into account.




  • Shai I, Schwarzfuchs D, Henkin Y. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Eng J Med . 2008 Jul 17;359(3):229-41.

Last reviewed August 2008 by Larissa J. Lucas, MD

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