Today we continually hear about the health benefits of following a Mediterranean diet. For example, a recent analysis of more than 50 published studies indicated that a Mediterranean diet would lead to a 30-percent reduction in metabolic syndrome (1). Since metabolic syndrome can be considered pre-diabetes, the public health implications are enormous. However, are we talking about the Spanish Mediterranean diet or the Italian, or the Moroccan, the Egyptian or the Lebanese versions? Here is the basic problem with all diets: Trying to define them correctly.
In order to compare one diet to another, each diet must ultimately be defined by its balance of the macronutrients (protein, carbohydrate and fat). This is because the macronutrient balance determines hormonal responses generated by that diet (2).
A Mediterranean diet can be considered to contain approximately 50 percent of the calories as carbohydrates, 20 percent of the calories as protein and 30 percent of the calories as fat. This is a higher protein-to-carbohydrate balance than is found in the usually recommended “healthy” diets for weight loss and cardiovascular health. As a result, this difference in the balance of the protein-to-carbohydrate ratio will generate different hormonal responses between the two types of diets, especially in terms of reducing insulin responses and controlling cellular inflammation.
This is important since it is excess insulin that makes you fat and keeps you fat, and it's cellular inflammation that makes you sick. Since insulin levels are determined by the protein-to-carbohydrate ratio, would more protein and less carbohydrate generate an even better response? Of course it would. That is why the Zone diet contains 40 percent of the calories as carbohydrates, 30 percent of the calories as protein, and 30 percent of the calories as fat. This improved protein-to-carbohydrate balance means lower insulin levels and less cellular inflammation.
Why stop there? Let's just continue reducing the carbohydrates. Now you get low-carbohydrate diets, like the Atkins diet. Unlike the Zone diet, carbohydrates are no longer the primary macronutrient in a true low-carbohydrate diet. Now the primary macronutrient is fat. Using these low-carbohydrate diets creates some real problems by generating an abnormal metabolic state known as ketosis. This occurs when you don't have enough carbohydrates (fewer than 20 percent of total calories) in the diet to metabolize fat completely to carbon dioxide and water. When that happens, your blood vessels lose their elastic nature, (3) increasing the risk of a heart attack (4). This is probably a consequence of lowering insulin too much as well as increasing inflammatory mediators (3). If you are trying to lose weight, increasing the likelihood of a heart attack is not a good idea. So it seems you need some carbohydrates, but not too few if your goal is to lose weight safely.
That's why people (as well as physicians and diet editors) get confused when they read articles in the New England Journal of Medicine talking about low-carbohydrate diets for weight loss when such diets actually contain 40 percent carbohydrates (5). To be correct, they should use the term “the Zone diet” instead of a “low-carbohydrate diet” to be correct. Despite the poor dietary description used in this article, the “low-carbohydrate” (aka the Zone) diet generated greater weight loss after two years, a greater reduction in the total cholesterol-to-HDL cholesterol (a marker of future cardiovascular risk), a greater decrease in triglycerides and a greater decrease in inflammatory markers when compared to a Mediterranean diet or the always-recommended low-fat diet (5). That's why you do controlled clinical trials instead of guessing what the best might be.
So if you want to lose weight and reduce your future heart disease risk, it seems prudent to follow the Zone diet and make most of your carbohydrates colorful ones (i.e., fruits and vegetables) and add olive oil and nuts for fat instead of using vegetable oils and saturated fats just as I recommended more than 15 years ago (2). Just call it the Mediterranean Zone diet. Now everyone is not only happy, but also they are finally using the proper diet terminology.
- Kastorini C-M, Milionis HJ, Esposito K, Giuglian D, Goudevnos JA, and Panagiotakos DB. “The effect of Mediterranean diet on metabolic syndrome and its components.” J Am Coll Cardiol 57: 1299-1313 (2011).
- Sears B. “The Zone.” Regan Books. New York, NY (1995).
- Buscemi S, Verga S, Tranchina MR, Cottone S, and Cerasola G. “Effects of hypocaloric very-low-carbohydrate diet vs. Mediterranean diet on endothelial function in obese women.” Eur J Clin Invest 39: 339-347 (2009).
- Yeboah J, Crouse JR, Hsu FC, Burke GL, and Herrington DM. “Brachial flow-mediated dilation predicts incident cardiovascular events in older adults.” J Am Coll Cardio 51: 997-1002 (2008).
- Shai I, Schwarzfuchs D, Henkin Y, Shahaar DR, Witkow S, Greenberg I, Golan R, Fraser D, boltin A, Vardi H, Tangi-Roxental O, Zuk-Ramot R, Sarusi B, Fricner D, Schwartz Z, Sheiner E, Marko R, Katorza E, Thiery J, Fielder GM, Bluher M, Stumvoll M and Stamper MJ. “Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet.” N Engl J Med 359: 229-241 (2008).