The front page of the Life section of my local paper featured an article by Janet Helm of the Chicago Tribune, complete with a nearly full-page photo of a crusty baguette and the headline “How Sweet it is: Diet Craze is Based on Glycemic Index”. The net effect clearly implying that bread is back and good for your weight loss. The first line of the article reads:
Following the low-carb flameout, the glycemic index may be poised to be the next big dieting trend.
The first line clearly laid bare the author’s bias and got my hackles up. Low-carb flameout? I would agree there was an unfortunate Roman candle trajectory for low-carb manufacturers of convenience and pre-packaged foods: a meteoric rise followed by a flameout that destroyed the good along with the bad and the ugly. But as far as I can see, there are still millions and millions of people devoted to the lower carb way of life; they’re just back to basics–meat, fish, poultry, eggs, cheese, greens, low-starch veggies, low-sugar fruits. You know the drill; we lived without pre-packaged convenience for decades and, for the most part, will do so happily again.
Which brings me back to the thrust of the article, which was not to malign low carb per se, but to examine what Ms. Helm refers to as potentially the “next big dieting trend”: The Glycemic Index.
The piece is actually pretty balanced in pro-ing and con-ing the notion of GI, for which I was grateful. For instance, she rightly points out that everyone doesn’t view the GI in the same favorable light and that even its developers never intended that this research tool be used as a weight loss gimmick. In fact, Ms. Helm quotes Dr. Susan Raatz’s October 2005 research study that compared weight loss between a standard low calorie diet and an isocaloric low calorie low GI diet and found no significant difference between the groups. In other words, eating low or high on the GI scale didn’t seem to matter if you ate little. (Perhaps they’d have found that it would matter more if you ate a lot of calories, but this study didn’t address that issue.)
We’ve always held that while there’s little inherently wrong with the general concept of eating whole foods that fall lower on the glycemic index versus ones that fall higher, there are some potholes one can fall into that will subvert the theoretical benefits of low GI dieting. For instance, if all you do is adhere to the dictum that low GI is good, whatever the food, that opens the door for the guiltless consumption of foods containing a fair amount of fructose–jelly beans, for instance–since compared to glucose, fructose falls much lower on the GI scale.
Fructose, about which we wrote extensively in our book, The Protein Power LifePlan (Warner 2000), isn’t metabolized in the same way as glucose; it’s able to skirt a couple of critical metabolic control points, and consequently, functions as what’s called a “lipogenic sugar,” meaning that instead of running blood sugar up, it drives the production of triglycerides. It does this so effectively that fructose feeding has long been a standard technique to make lab animals insulin resistant, with fatty livers and diabetes. Human research shows that it does pretty much the same thing to people. If you drive triglyceride production even on low GI foods, you wind up stuffing fat into your liver cells and will put yourself on the road to insulin resistance and all its potential health risks.
In the long run, a low GI diet–regardless of what you call it–will only work for weight loss if it’s also a low carb or low calorie one. No one will lose weight on an excess of low glycemic calories, just as no one will lose weight on an excess of low carb calories or low fat calories.
When queried in the past about the GI, we’ve always maintained is that if you keep your carbs low, it probably doesn’t really matter whether a food is low GI or not. If you don’t have many glycimes, their index rank means a whole lot less. After all, 5 grams of carb eaten as rice doesn’t do a whole lot more to blood sugar than 5 grams as broccoli. The difference is that 5 grams of rice is about a teaspoon and a half and 5 grams of broccoli is over a cup. For most people, that volume disparity alone will encourage a better glycemic choice. And to us, that’s the name of the glycemic game, learning to spend your carbs wisely, on foods packed with micronutrient density, but light in starch or sugar. It’s when you raise up the number of carbs per meal or snack that the GI effect may play more of a role–i.e., not in weight loss or correction, but in weight and health maintenance.
That said, however, in our experience, it’s more the amount of carb at a sitting that determines the metabolic effect, not the GI of the carb. In the corrective phases of dieting–during weight loss or while trying to regain control of blood sugar, blood pressure, blood lipids, or reverse GERD–keeping carbs at 7 to 10 grams of effective (net) carb a meal will do the trick. Our method of accounting for (subtracting) the fiber content in arriving at effective grams of carb does pretty much the same thing as the glycemic index in steering the user toward a more nutritious class of foods, but wouldn’t let the higher carb, low GI things like jelly beans slip through–at least not many of them at a time.
So our advice is, as it has always been, that you surround your meat, fish, poultry, eggs, nuts, seeds, and dairy with controlled portions of lower-starch, lower-sugar, higher-fiber, micronutrient-denser fruits and veggies and call it by whatever name melts your butter.