Is low glycemic index the next big thing for weight-loss?

I’d like to take a look at two weight loss studies that got some media attention lately, one of them receiving much more notice than the other.

Mark Haub, a professor of human nutrition at Kansas State University lost 27 pounds in 10 weeks on what he calls the “convenience store diet” or what others dubbed the Twinkie diet. Haub adhered to a calorie restricted diet that consisted of junk food and a few veggies, washed down with a multivitamin and a protein shake. Haub was able to prove that a calorie’s a calorie, and what matters is the bottom line: Less calories in than out equals weight loss. His experiment is ongoing, but at this point short lived, and the small study group (of just one), lack of control, and absent objectivity make this study not-so-scientific but good enough for coverage in all the popular news outlets (CNN, LA Times, Fox, CBS, Chicago Tribune to name a few).

Which is good thing, because if we all internalized the fact that calories matter we’d be immune to scam diets – unbelievably still heavily advertized – which promise weight loss without calorie restriction.

The other study is a scientific one, published in the New England Journal of Medicine. The study included 733 participants, from 8 European countries, who already lost at least 8 percent of their body weight on a very low calorie diet. The participants were randomly assigned to one of five diets for weight maintenance: A low-protein diet with a high glycemic index (GI); a low-protein, low-GI diet; a high-protein, low-GI diet; a high-protein, high-GI diet, or a control diet which followed the current dietary recommendations without special instructions regarding protein or GI.

Short intro to glycemic index: The glycemic index, developed initially for the treatment of diabetes, ranks carbohydrate containing foods based on how they affect blood sugar level when eaten in isolation. Carbs that break down quickly, like white bread and potatoes, have a high GI, and those that release sugar into the blood stream more gradually, like fruit, have a low GI. Foods are scored on a scale of 0 to 100.

One important thing to remember about this study: The participants were not calorie restricted. They were allowed to eat as much as they felt they needed as long as they stayed within the rules regarding the protein and carbs proportion and quality.

And the results: After 6 months weight regain was 2 kg (about 4.5 pounds) higher in the high GI/low protein group, compared to the low GI/high protein group. More people in the low GI/high protein group were able to stay on track and complete the study.

At 6 months we have a clear winner here. So far so good. But let’s not get over excited.

Is the glycemic index the next big thing in weight loss?

When it comes to weight loss what matters most is calories. Any plan that results in a net deficit of calories will lead to weight loss. But, not all calories are the same, not when it comes to weight loss, and not when it comes to health. Some calories come from foods that fill you up, and some calories come from foods that create very little satiety. Some calories come from foods with virtually nothing besides sugar and junk, while other calories are part of a food that supplies many nutrients our body needs.

The low GI diet is an interesting concept. Blood glucose fluctuations elicit a cascade of hormonal reactions, which potentially affect both metabolism and hunger, and this diet’s ability to decrease hunger and control weight regain showed some promise is studies. It would be very interesting to see how this studied group fares as time goes by. Six months is still short term when it comes to weight regain.

Is GI going to be the next diet fad? GI is garnering attention and many popular commercial diets and diet books – including the South Beach Diet, Nutrisystem, the Zone diet and Sugar Busters – are based at least in part on the GI. The GI has a growing following especially in Australia and in the UK, and a new GI Symbol now appears on foods, signifying their tested GI value.

Low GI corresponds quite often with the age-old understanding of what’s good to eat. Most highly processed grain products have a high GI, whereas minimally processed grains, whole fruits, legumes, and non-starchy vegetables tend to have a moderate or low GI. On the other hand pure fructose and ice cream have a very low GI, table sugar and high fructose corn syrup have only a moderate GI, and potatoes and white rice are the root of all GI evil, with a GI of about 100.

A few other things that will curb your enthusiasm for the GI: It’s difficult (and costly) to test, there’s inter-lab variability, although the type and proportion of sugar or starch in a food affects GI, so do a lot of other factors in the meal—the way the food’s been cooked, the presence of fiber, protein, fat, alcohol or acid will all affect the glucose response—and there’s plenty of inter-personal variability. Finally, the GI of the food matters much less than how much of that food you’re eating. To be quite honest, even diligent adherence to GI charts will leave you guessing about your own sugar level fluctuation after a meal.

At this point, GI for weight-loss is neither practical nor is its validity fully established.

Here’s another thing that troubles me: The GI concept can help create a whole new line of health-halo adorned highly processed foods, and be abused in much the same way as other nutrition buzzwords have been before it. Adding vitamins to junk has added nothing but confusion, and replacing butter with hydrogenated vegetable oil actually blocked arteries. Replacing sugar with fructose will lower the lab-tested GI while — most likely — add nothing to our health and may do harm.

Have you tried using the glycemic index?

Dr. Ayala