South Beach Diet

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History and theory

While Agatston accepted the prevailing wisdom among cardiologists that a low-fat diet would reduce cholesterol and prevent heart disease, he found that, in practice, patients had a difficult time sticking to the diet. To explain this failure, he turned to the scientific work with insulin resistance which led David J. Jenkins to develop the glycemic index in the early 1980s. When sugar enters the bloodstream, the pancreas secretes insulin which triggers cells to absorb the sugar. Many years of introducing quick bursts of sugar would eventually result in cells becoming resistant to insulin. This resistance would leave sugar in the bloodstream longer which would then cause the pancreas to release even more insulin. This excess insulin would eventually drive blood sugar below normal levels. Jenkins (and others) discovered that, in addition to potentially causing diabetes, this effect would also produce cycles of hunger. Excess sugar consumption led to excess insulin which led to low blood sugar which led to hunger pangs which led to the consumption of more sugar.

Agatston postulated that patients on low-fat diets were eating no less food than they had been before they started the diet. They simply had compensated for the fat by consuming additional sugar and simple carbohydrates (which are rapidly reduced to sugar by the digestion process). This led to the cycles of hunger that Jenkins had described. As a result of this hunger, patients were consuming excess calories and gaining weight, ironically defeating their attempt to reduce the risk of heart disease.

Agatston was aware of the low-carbohydrate diet popularized by Robert Atkins in the 1970s, but he feared that this diet would lead to too few carbohydrates, too much saturated fat, too little fiber, and a number of maladies including an increased risk of heart disease.

The diet

The South Beach Diet is relatively simple in principle. It replaces "bad carbs" and "bad fats" with "good carbs" and "good fats."

"Good carbs" vs "bad carbs"

According to Agatston, hunger cycles are triggered not by carbohydrates in general, but by carbohydrate-rich foods that the body digests quickly, creating a spike in blood sugar. Such foods include the heavily refined sugars and grains that make up a large part of the typical Western diet. The South Beach Diet eliminates these carbohydrate sources in favor of relatively unprocessed foods such as vegetables, beans, and whole grains. Carbohydrate sources are considered "good" only if they have a low glycemic index

"Good fats" vs "bad fats"

The South Beach Diet eliminates trans-fats and discourages saturated fats, replacing them with foods rich in unsaturated fats and omega-3 fatty acid. Specifically, the diet excludes the fatty portions of red meat and poultry, replacing them with lean meats, nuts, and oily fish.


Agatston divides the South Beach Diet into three phases, each progressively becoming more liberal. "Phase 1" lasts for the first two weeks of the diet. It eliminates all sugars, processed carbohydrates, fruits, and some higher-glycemic vegetables as well. Its main purpose is to get rid of the hunger cycle. "Phase 2" continues as long as the dieter wishes to lose weight. It re-introduces most fruits and vegetables and some whole grains as well. "Phase 3" is the maintenance phase and lasts for life. There is no specific list of permitted and prohibited foods. Dieters are expected to take what they have learned and apply it to their life without any guidance.

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