High-protein, low-carb diets: Are they healthy?
The straight goods on a healthy program that lets you slim down and have your carbs, too
by Anne Lindsay


By now most of you have likely heard or read about the high-protein, low-carbohydrate diets that have been the rage among the overweight. You may even be like some of my friends who are following Mastering The Zone, or Dr. Atkins' New Diet Revolution, or Protein Power. They tell me how much weight they've lost and how good they feel. What's more, some dieters find the high-protein, low-carbohydrate diets easy to follow because they don't have the hunger and cravings associated with most diets.

I tell them that of course they'll lose weight on these diets – after all, they're reducing their calorie intakes. But high-protein, low-carbohydrate diets prompt the body to make an excessive amount of chemicals called ketones, which creates a state known as ketosis. This state makes dieters feel queasy and light-headed and lose much of their desire for food. Lose the desire for food? Great, you say. Why not simply stay on these diets and be eternally thin?

One reason is that the authors of most of these diet books have never published data to validate their claims. Low-carbohydrate diets do work in the short run. For certain medical situations your doctor may even recommend one.

However, there are several downsides to following a high-protein, low-carbohydrate diet for a prolonged length of time. Now a little-known but well-researched book, The Glucose Revolution, explains why you should eat carbohydrates and how you can lose weight while including them in a balanced, healthy diet. It recommends certain carbohydrates according to their ranking on the glycemic index (GI), a rating system that shows how quickly various carbohydrates raise blood-glucose levels.

Diet theories
Most of the best-selling diet books are based on the premise that a diet high in carbohydrates causes a rise in blood-sugar levels, which results in high blood-insulin levels. They conclude that high blood-insulin levels result in weight gain.

The Glucose Revolution, which refutes much of the popular (and unproved) diet information on carbohydrates, was written by Canadian Dr. Thomas Wolever, a world-renowned expert on glucose. Wolever, who is also a professor in the department of nutritional sciences at the University of Toronto, wrote the book along with three other nutritional and medical researchers.

All the books agree that high blood-insulin levels are associated with obesity. But Wolever and his coauthors disagree with the other authors on how to lower those levels and what constitutes a healthy diet. Their book shows why we should eat a carbohydrate-based diet, how we can do it and lose weight, and how to control our blood glucose (Dr. Wolever says that the term blood sugar is technically incorrect). It also shows that we gain weight only when we eat more carbohydrates than we need for energy.

Fast foods
Wolever helped develop the glycemic index with Dr. David Jenkins at the University of Toronto. The index ranks carbohydrate foods by their immediate effect on the body's blood glucose. Foods with a low GI raise blood glucose the least. If we eat carbohydrates that have a low GI we can control our blood-glucose levels and our insulin levels. (Remember, high insulin levels are associated with weight gain.) This means we don't need to follow a restrictive and unbalanced low-carbohydrate diet to lower insulin levels and lose weight.

Quick digestion results in a fast rise in blood-glucose levels, which in turn causes a rise in blood-insulin levels. We used to think that our bodies digested simple carbohydrates (in the form of simple sugars, such as candy or sweets) quickly. We also thought that we digested complex carbohydrates, such as breads, pasta and rice, slowly. Wolever points out that our assumptions about the speed at which foods are digested were wrong. Many starchy foods, such as bread and potatoes, are digested quickly, while moderate amounts of most sugary foods, such as candy and ice cream, won't produce huge surges in blood glucose.

Research reported in The Glucose Revolution shows that slower digestion helps to delay hunger pangs and promote weight loss in overweight people. Low-GI foods help you to burn more body fat and less muscle.

Wolever says that other popular diet books use the glycemic index but they misrepresent it. “Any book that cautions against pasta isn't right,” he notes, since pasta has a low GI. As well, some very nutritious foods, such as fruit, have a moderately high GI ranking but shouldn't be avoided. “It's important to eat a variety of foods,” he says. “Just include more carbohydrate foods with a low GI.” And avoid highly refined foods.

The bottom line: To lose weight you still have to exercise and limit calories. You can lose weight on high-protein, low-carbohydrate diets, but following them is not smart eating. Eat a healthy, balanced diet – one that doesn't severely restrict foods you love to eat.


Canadian Living, March 2000