Tufts University School of Nutrition

Weighing In On the South Beach Diet
Tufts Health and Nutrition Letter 22 (2004):1.
Weighing In On the South Beach Diet

The content of our Tufts Health and Nutrition Letter is based substantially from the research and expertise of the Gerald J. & Dorothy R. Friedman School of Nutrition Science and Policy, the only graduate and professional school of nutrition in North America.

IT’S NEVER a good sign when a weight-loss plan promises that you won’t “suffer any hunger pangs” and that your cravings, especially for foods like sweets and baked goods, “will virtually disappear” within the first week. But it sure does seem to help a diet book leapfrog to the top of the New York Times bestseller list. Enter The South Beach Diet: The Delicious, Doctor-Designed, Foolproof Plan for Fast and Healthy Weight Loss, by Arthur Agatston, MD.

We combed the book cover to cover, allowing for the possibility that the hype used to attract buyers might belie a healthful, scientifically grounded weight-loss plan within. But that was not to be the case. Disappointingly, the South Beach Diet is simply yet another version of a fad wrapped within a gimmick. The fad here is the low-carb craze; the gimmick, the fact that this particular incarnation of low-carb is not high in saturated fat, like the Atkins plan. That’s certainly a good adjustment. But like all too many popular diet books, this one is replete with faulty science, glaring nutrition inaccuracies, contradictions, and claims of scientific evidence minus the actual evidence.

Faulty science

The premise of the book is that many foods high in carbohydrates send blood sugar soaring too high too fast, which then gets the hormone insulin in gear to take sugar out of the bloodstream. But the insulin overshoots its mark, causing blood sugar to plunge and leading to reactive hypoglycemia, which in turn produces feelings of incredible hunger and cravings for more carbs that keep the vicious cycle going. Dr. Agatston refers to the process as “the dreaded acute rise and fall of blood sugar level, creating more cravings later on,” and he says that eating “a baked potato in mid- afternoon practically guarantees that you’ll be starving for carbs by dinner.” It’s eating “bad” carbohydrates, he comments, not eating too many calories, that “ultimately is responsible for our epidemic of obesity.”

There’s just one problem. Unless you have diabetes, blood sugar remains in a remarkably stable range. Yes, it may drop lower after eating a hot fudge sundae than after eating a salmon steak on a bed of lettuce. But, points out Christine L. Pelkman, PhD, who studies blood sugar responses to carbohydrate at the State University of New York

Can Jump-Start Your Fitness Routine Weighing In On the South Beach Diet Continued from page 1 at Buffalo, research that has looked at this issue simply has not linked relatively low blood sugar to hunger. “‘At most,” she says, “it’s a minor player in the hunger/satiety mechanism, with many other hormones and bodily reactions coming into play.”

Still, the book plows on. Out of Dr. Agatston’s faulty premise come instructions to avoid most carbohydrate-rich foods for the first 2 weeks, then gradually add back “good” carbs such as whole-wheat bread and certain vegetables and fruits that he says don’t cause the out-of-hand spikes and subsequent drops in blood sugar.

The lack of carbs is largely what leads to his promised 8- to 13-pound weight loss in those first weeks. Consider that carbohydrates are stored in the body attached to water molecules. When carbs are not taken in with the diet, every carb that comes out of storage to fuel the various organs and other tissues releases water, which ends up in urine and creates weight loss on the scale that can be confused with fat loss.

The carbs that should be allowed back after the initial 2-week phase, says Dr. Agatston, are low on a scale called the Glycemic Index, meaning they are absorbed slowly and thereby raise (and ultimately) lower blood sugar more slowly than other carbs. But the numbers on the Glycemic Index scale don’t jibe with his instructions. For instance, he says white bread is worse for you than sugar, but on the scale, a hamburger bun, made of white bread, has a better number than whole-wheat bread, which he recommends. Similarly confusing, artificially sweetened chocolate milk comes out looking better for you than plain skim milk, and fettuccine is preferred to linguine (even though they are exactly the same food with slightly different thicknesses to their strands).

Inconsistencies abound

The faulty and confusing science is compounded by The South Beach Diet’s own internal inconsistencies. For example, on pages 13 and 27, the book says that the diet is “distinguished by the absence of calorie counts…or even rules about portion size” and that you should not “even think about limiting the amount you eat,” then proceeds to count calories and measure out servings every step of the way. Turn to page 28, and Dr. Agatston says that “I recommend counting out 15 almonds or cashews.” And his recipes at the back of the book all say clearly how many servings each one contains, with how many calories.

Among the other inconsistencies: foods to avoid or eat rarely in phase 2 of the diet include bananas, yet one of the desserts recommended for that phase is sliced bananas dipped in sugar-free chocolate sauce; and whole and intact foods are better for you than mashed, but mashed potatoes are better than whole baked ones. (Yes, you read that correctly. Those two mutually exclusive “facts” can be found on page 54.)

Then there are the out-and-out food and nutrition inaccuracies. One is that whole-wheat bread is not whole grain. (It is. Wheat is a grain, and if it’s whole, it’s whole grain.) Another is that the pulp in juice is a source of fiber (Nope). A third is that couscous is a whole grain. (Also nope.) And yet another is that watermelon is full of sugar but that cantaloupe is not. (Both a cup of watermelon and a cup of cantaloupe pieces have 14 grams of sugar.) For a cardiologist who says, “I feel nearly as comfortable in the world of nutrition as I do among cardiologists,” Dr. Agatston has sprinkled an awful lot of nutrition gaffes throughout his book.

More usual diet-book suspects

Like a lot of other weight-loss books, The South Beach Diet says the program “has been scientifically studied” and “proven effective,” then offers up not a single reference in a scientific journal. Instead, it refers only to presentations of data made at scientific meetings, which, unlike research that finally makes it to publication, do not first undergo rigorous review by other, uninvolved investigators in the field to see if the scientific methodology is sound.

The book also gives a lot of clich├ęd advice that you don’t need to spend $24.95 to hear yet again: don’t go to a restaurant starving; don’t eat the bread brought to the table before the meal; eat just a few bites of chocolate cake for dessert rather than the whole thing; and so on.

The South Beach Diet gives some just-plain-weird advice, too: have ice cream instead of white bread because it’s less fattening (if only!); a baked potato topped with low-fat cheese or sour cream is less fattening than a plain one; and don’t drink beer because it loads directly to fat deposits on your belly (as if calories from particular foods ended up at particular body parts and you could decide with your food choices where you’re going to gain or lose weight).

That said, the South Beach Diet isn’t the worst weight-loss plan in the world. We’ve seen worse, and following it for a while isn’t going to kill you (although it is low in calcium and some other essential nutrients). You’ll even lose weight on it. But it will have nothing to do with your blood sugar or carbohydrates’ effect on the body. It’s because, in keeping with the broken promise that calories don’t have to be counted, the daily menus are assiduously calorie-controlled, generally containing somewhat fewer than 1,500 calories a day for phase 1 and closer to 1,500 or 1,600 for phase 2.

In other words, when Ur. Agatston says your carbs will “drop dramatically” if you replace your typical cheeseburger, fries, and Coke with an open-topped, half-bunless burger, a salad, and a diet soda, what’s going unsaid is that your calories will drop dramatically, too.

But you already knew that less bread, a salad instead of fries, and a diet soda instead of regular would help your weight-loss effort. You don’t need a 300-page book based on fallacies about carbohydrates to figure it out.