The premise behind the book is that overindulging in highly processed "bad" carbohydrates raises blood glucose levels, leading to surges in insulin that cause sugar cravings and weight gain. By limiting such carbohydrates, the South Beach diet suggests that you can virtually eliminate cravings for carbohydrates, including sugar cravings, and lose weight – all without counting calories or measuring portion sizes. Dr. Agatston also argues that replacing bad carbohydrates with "good" ones will "clear up" insulin resistance – a decreased ability of the body’s tissues to respond to insulin, which is associated with an increased risk of diabetes and cardiovascular disease.
The rationale behind the South Beach meal plan is the glycemic index, which has become a trendy concept in weight loss. The index assigns each food a number based on the rise in blood glucose it causes during the first two hours after it is eaten, compared with the rise triggered by an equal amount of carbohydrate in a standard food like white bread. The diet calls for choosing foods that are low on the glycemic index (most vegetables and legumes, for example) in order to avoid surges in blood glucose. The book suggests that consuming low-glycemic index foods will also curb your appetite and minimize your cravings. The problem with that claim is that researches that have been done to look at this issue have simply failed to link relatively low blood sugar to hunger.
As for insulin resistance, Dr. Agatston oversimplifies a complex disorder. Although obesity is a common cause, genetic factors, diet, physical inactivity, smoking, family history of diabetes in a first-degree relative, and older age also contribute. And the fact is that the evidence indicates that for people who are overweight and insulin-resistant, any diet promoting weight loss, even if it is high in carbohydrates, will improve insulin sensitivity.
The faulty and confusing science is compounded by the South Beach Diet’s own internal inconsistencies. For example, it claims to have no rules for calorie counts or portion sizes yet the recipes all say clearly how many servings each one contains, with how many calories. And there are 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 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 have 14 gms. of sugar.)
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 leads 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).
But the loss of carbs is largely what leads to the promised eight- 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.
Despite these limitations, the South Beach diet does encourage some good eating habits, particularly choosing whole-grain foods and fruits and vegetables over processed carbohydrates. As Dr. Agatston points out, these foods contain fiber, which helps fill you up, but are low in fat and calories. They also contain essential nutrients that help prevent disease. Furthermore, unlike Dr. Robert Atkins, who first popularized low-carbohydrate eating, Dr. Agatston focuses on lean meats, low-fat dairy products, and healthy sources of fats, like nuts and fish.
Phase 1 severely limits carbohydrates, and several clinical trials over the last few years have shown that dieters do lose weight on those types of meal plans – in the short time. It’s possible that the initial weight loss will motivate people to remain on the diet. Phase 2 calls for filling up on lots of fruits and vegetables along with lean meats and reduced-fat cheeses – a reasonable way to continue losing weight. Finally, Phase 3 allows for more carbohydrates from fruits and whole grains – a sensible plan for maintenance.
Of course, exercise is also a critical component of any weight-loss program. Dr. Agatston claims that the South Beach diet doesn’t depend on exercise in order to work, but studies have shown that people who exercise are more likely to maintain their weight loss. It’s also important that people with insulin resistance, which includes nearly everyone with type 2 diabetes, consult their physicians before starting this or any other special dietary regimen.
So, can a glitzy-sounding diet whittle your waist and improve your health at the same time? The South Beach diet may lack scientific proof and offer some dubious claims, but there are some experts who think that with its healthier choices, compared to other low-carb diets, it just might do so.