In this country, our epidemic of obesity and diabetes really took off over the past three decades and has continued at a fast clip right up to the present. Coinciden-tally, the 1980s was when the federal government, along with medical groups such as the American Heart Association, began to aggressively promote the benefits of a low-fat, high-carbohydrate diet. This was eventually reflected by the first USDA Food Pyramid, published in 1992, which emphasized bread, rice, pasta, and cereals as the basis of a healthy diet. Fats and oils were to be used sparingly. Was this the wrong advice? Did it have a role in the fattening of America? I believe the answers to these two questions are yes and yes.
The national recommendations were based on what was felt to be the best scientific evidence at the time. Much, if not most, of the nutritional research we have today was simply not available back then. The rationale for the low-fat, high-carb approach was largely predicated upon population studies performed after World War II. How did we go so wrong?
At the time of the national recommendations, the thought was that the new American diet would mimic the diet composition of the nonindustrialized world, where there was almost no obesity or heart disease. The problem was that in the national recommendations, no distinction was drawn between good carbs and bad carbs or between good fats and bad fats. While sugar was not recom-mended, starches (the so-called complex carbohydrates) were. It was simply not known at the time that low-fiber starches, such as white bread and potatoes, raised blood sugar just about as fast as simple sugars did. As for fats, studies showing the overall health benefits of good fats (such as omega-3-rich oils), including their positive effects on the heart, had not yet been performed.
In response to the conventional-and misguided-wisdom of the time, the food industry began to produce low-fat, low-cholesterol baked goods, including cookies and pastries, made with refined white flour and varying amounts of sugar. Most commercial baked goods also included coconut and/or palm oil, which had replaced the highly saturated animal fats in these products when various groups complained about them. It was only when the American Medical Association published a position statement calling for clear disclosure to the public that tropical oils were just as highly saturated as animal fats that these plant oils began to be removed.
That's when things got even worse. Tropical oils were replaced by hydrogenated or partially hydrogenated vegetable oils, which are directly associated with heart attack, stroke, diabetes, and other serious health problems. Ironically, trans fats were created as a healthier alternative to saturated fats, but they turned out to be worse. For years, most Americans (including yours truly) thought we could eat these starchy, trans fat-laden baked goods with impunity. We were mistaken. And we got fat.
How Eating Can Make You Hungry-and Fat
Thanks to ongoing research in the science of food, nutrition, and diabetes, by the early 1990s, I had a pretty good idea of where our diet had gone wrong. It became clear that as a society, in our attempt to limit fat, we were consuming ever-higher amounts of bad carbohydrates-in other words, more of the sugary sweets and refined starches that are essentially devoid of fiber and other nutrients. This was causing exaggerated swings in our blood sugar, which resulted in cravings for more refined carbs and constant hunger.
The reason we were so hungry all the time also became clearer when I learned about the glycemic index, a measure of how the carbohydrates in an individual food can affect blood sugar. The foods that keep blood sugar nice and stable-the ones that don't cause dramatic blood sugar swings-are those that are low on the glycemic index. These include whole grains, most vegetables, and low-sugar fruits (such as berries), which are digested slowly, making you feel full and satisfied for a longer period of time. Fiber is a major determinant in establishing a food's glycemic index, but there are other factors as well, such as the degree to which a food is processed, how long it's cooked, and its acidity.
However, as useful as the glycemic index can be for guesstimating how certain foods will affect your blood sugar levels, it doesn't tell the whole story. We have learned a great deal more about food and how it works in our bodies since the glycemic index was first identified.
It's no wonder that back then my patients were getting fatter as they filled up on the high-glycemic carbs (the pastas, breads, and cereals made from white flour) that we were mistakenly recommending as a substitute for fatty meats and full-fat dairy. Once I understood more about the glycemic index, however, it didn't take me long to see that these essentially fiberless, starch-laden foods were making our patients hungrier due to the swings in their blood sugar.
And, of course, the hungrier they got, the more they ate, and the more weight they gained. It was an endless cycle. And as they got fatter, they also became predia-betic and diabetic. Because of new research in this area, I also began to under-stand that there were just as many misperceptions about these diseases as there were about what constitutes a good diet.
All the studies tell the same story. Our focus should be on nutrient-dense, fiber-rich carbohydrates, healthy sources of unsaturated fats, low-fat dairy and lean sources of protein. The principles of the South Beach Diet are here to stay.