Low-carbohydrate diets have been making a strong comeback in the last few years after losing popularity in the Eighties. All you have to do is spend some time at the health and fitness aisle of any major bookstore to discover dozens of books on various forms of the low-carbohydrate diet. Among the more popular these days are The Zone, Protein Power, Sugar Busters, Dr. Atkins New Diet Revolution, The Carbohydrate Addict, etc. They do not all agree with each other about the exact amounts of protein, fat or carbohydrates but bottom line is that they blame obesity on carbohydrates and insulin. In a nutshell, they claim that eating carbohydrates (starchy and sugary food) leads to insulin resistance, which in turn leads to obesity.
These books claim to have scientific evidence to back up their theories and some even list their scientific sources. Many of the books read like an advanced science textbook. Numerous people tell me that they don't really understand all the "scientific" explanations but they feel the authors must be right because, after all, they refer to so many research studies.
However, even best selling authors can misinterpret research studies. A case in point is the work of Dr. Gerard Reaven, an endocrinologist at Stanford University. Many of the low-carbohydrate diet books list his research as part of their "proof" that their theories are correct.
Yet, Dr. Reaven recently told Bonnie Liebmann of the Nutrition Action Health Letter (March 2000) that they all misunderstand his work. He said he was "upset about the misinformation" in these books. So upset that he came up with his own book, "Syndrome X: Overcoming the Silent Killer that Can Give You a Heart Attack".
"Syndrome X" or "The Metabolic Syndrome" is the term coined by Reaven in 1988 to describe the symptoms associated with insulin-resistance. These symptoms include high insulin levels, high triglycerides, high blood pressure, low HDL (good) cholesterol, and a reduced ability to break up blood clots.
What is insulin resistance?
A person who is insulin-resistant is not considered a diabetic but his or her insulin (a hormone secreted by the pancreas) cannot move glucose or sugar very efficiently from the blood into muscle and fat cells whenever this type of person eats carbohydrates. This means that although they have enough insulin to prevent blood sugar levels from rising too high, their pancreas secrete more insulin than is necessary. The excess insulin that is left in the bloodstream is what causes the symptoms mentioned above.
Insulin resistant people more prone to heart attack
According to Reaven, his studies indicate that insulin-resistant individuals are more prone to heart attack than normal people. He claims that people with insulin resistance should not eat high carbohydrate diets (he recommends 45% carbohydrates, 15% protein and 40% fat). However, this is to prevent too much insulin from being made and increasing the risk of heart disease and not, as the low-carb books claim, to prevent obesity. Reaven stresses that it is only insulin-resistant people and diabetics who have to limit their intake of carbohydrates. Normal people can eat low-fat, high carbohydrate diets without having to worry about increasing their risk of heart disease.
Excess calories make you fat
In another interview with Liebmann in 1996, also for Nutrition Action Health Letter, Reaven said "There are so many studies showing that if you decrease calories, people lose weight, and it doesn't matter if you do it by cutting fat, protein, or carbohydrate. A calorie is a calorie is a calorie."
He added, "Carbs don't make you fat, and insulin doesn't make you fat, as the books claim. Calories make you fat. It's like a bankbook. It's a matter of how much you put in and how much you take out. The more you eat and the fewer calories you burn up, the heavier you'll get. The law of thermodynamics, to the best of my knowledge, hasn't been repealed recently."
Insulin resistance does not cause obesity
Reaven emphatically says that insulin resistance does not cause obesity. In his own words: "Years ago, we put people with different degrees of insulin resistance on dramatically different diets - in one study, carbohydrates were either 85 or 17 percent of the calories. The only thing that affected their weight was how many calories they ate. More recently, we've published long-term studies showing that weight gain is unrelated to how insulin-resistant people were when the studies began. And weight loss with low-calorie diets is also unrelated to the degree of insulin resistance. So there's not one shred of evidence that insulin resistance causes obesity".
He further explains, "If you think about it, the notion that insulin resistance causes obesity is unreasonable. Insulin resistance means that insulin isn't acting correctly. So if you don't have enough insulin or if your cells aren't responding to insulin, you can't deposit glucose into cells. If anything, you would lose weight."
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