The South Beach Diet

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The South Beach Diet

The South Beach Diet by Dr. Agatston is currently ranking as the number-five best-seller on Amazon. This book is an amalgamation of mostly sensible advice about ?good? and ?bad? types of fats and carbohydrates. The diet itself starts out, like the ?Protein Power? diet by the Eadeses or the Atkins diet, by severely restricting dietary carbohydrate. This produces rapid weight loss in the first 2 weeks (called ?Phase 1?), although much of the weight loss will be due to fluid and glycogen loss, not body fat. During ?Phase 2,? Dr. Agatston?s plan begins to gradually add back what he calls ?good carbs.? This includes foods such as low-glycemic-index (GI) fruits, beans and whole grains. You stay in Phase 2 until your target weight is attained.

?Phase 3? allows more ?good carbs? but now includes some with a higher GI such as whole-grain breads, pasta, rice, tortillas and potatoes. These high-GI foods can only be eaten occasionally and in limited amounts. ?Phase 3? eliminates the two daytime snacks allowed in ?Phase 2.? Unlike some authors, Dr. Agatston does not obsess about the ratio of fat to protein to carbohydrate.

Like many popular fad diet authors, Dr. Agatston blames the growing waistlines of Americans on high-GI foods and excessive insulin release. Like Sears (Enter the Zone) and the Sugar Busters! authors, he claims high-GI foods trigger excessive insulin release that leads eventually to dietary carbohydrates turning into body fat. Like other fad diet book authors, Dr. Agatston claims adding fat or protein to high-carbohydrate foods such as potatoes will reduce the insulin response and help prevent excessive hunger and cravings.

? On page 54 he claims ?Even French fries are better than baked [potatoes], because of the fat in which they?re cooked. Of course the same is true for potato chips.? Why? Because he says the fat ?slows the digestive process.?

? On page 55 he claims eating some steak with a baked potato ?? renders it better for your diet than a potato on its own.? This is because he apparently believes that the addition of fat and protein to carbohydrate will cause your body to make less insulin. In fact adding fat and/or protein to a potato will actually increase insulin release, not lower it.

Dr. Agatston also reincarnates the claims of the late Carlton Fredericks and others who for years blamed refined carbohydrates for causing excessive insulin output followed a few hours later by a ?reactive hypoglycemia? (page 62). He, like Fredericks before him, claims it is this reactive hypoglycemia that triggers extreme hunger, cravings and excessive calorie intake and weight gain. In fact, there is no credible research showing ?reactive hypoglycemia? leads to weight gain. Blaming all foods with a high GI for obesity is too simplistic. In fact, the much-maligned white potato was shown to have the highest satiety index compared to a wide variety of other foods.1 This study showed that people felt more satisfied and also ate less 2 hours after eating a potato than after eating the same calorie intake from steak, fish, eggs and many other low-GI foods. This finding directly refutes one of the central tenets of The South Beach Diet.

The theory that a diet with a high GI or even a high glycemic load promotes obesity is also far fetched. One of the highest-GI foods is the sticky rice favored by the Japanese who have about one-tenth the incidence of obesity as Americans. In the 1970s the Japanese ate an extremely high GI and glycemic load diet and yet obesity, diabetes and coronary heart disease were far less common than in the United States where the GI of the diet was lower. Indeed, as more fat has entered the Japanese diet calorie intake has increased and obesity, diabetes and coronary artery disease are all increasing.

Contrary to Dr. Agatston?s claims, there is far more research linking obesity to high-fat diets with a high calorie density than to high-GI foods such as potatoes and beets. Agatston makes many claimsthat are either known to be wrong or likely to be wrong. For example, it has been proven that adding fat or protein to carbohydrate increases rather than decreases as he claims the release of insulin. It has also been clearly demonstrated that adding fat to lowfat foods dramatically increases ad libitum calorie intake.2 Simply put, when dietary fat is increased, increasing the calorie density of the diet, nearly all people will increase their calorie intake and gain weight.

Bottom Line:

Dr. Agatston?s diet may help people lose weight, not for the reasons he claims but because his diet is higher in fiber and has a lower calorie density than what most Americans now eat. Certainly eating far less sugar and refined grains is good advice, but ignoring the role of fat in promoting excessive calorie intake is unwise.

By J. Kenney, PhD, RD, LD, FACN.


1. Am J Clin Nutr 1997;66:1264-76

2. Am J Clin Nutr 1987;46:886-92

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