University of Toronto study showed those on low-glycemic diet lost weight without trying
The study pooled together data from all previous studies on glycemic index and found a reduction in hemoblogin A1c levels.
By Christine SismondoSpecial to the StarMon., Jan. 3, 2022timer4 min. readJOIN THE CONVERSATION ( 15 )
Want to lose weight without even trying?
Who doesn’t? That’s the kind of pitch line you might see right before you take the bait and click the link to a dodgy weight-loss scheme, right? Interestingly enough, though, recent research — real university research — discovered unintentional weight loss in people who, for an average of 12 weeks, trialed the low glycemic index (GI) diet.
Now, to be clear, it wasn’t much weight; the average was just over one pound. Consider this, though: there was no calorie restriction. Nor was it time-restricted eating because the studies weren’t designed as weight loss schemes. That was just a happy “side effect.”
The systematic review and meta-analysis, conducted at the University of Toronto’s Department of Nutritional Sciences, was actually designed to consolidate the evidence from all previously published randomized controlled trials, to see if a low-GI diet could reduce hemoglobin A1c (HbA1c) levels, which are sort of like blood sugar levels, except they measure a longer-term trend and are used to diagnose diabetes and prediabetes. The study found that in the 29 published trials, low GI diets did, in fact, have a “clinically meaningful” effect on the HbA1c levels and it moved them in the right direction.
In fact, if the diet were a drug (it isn’t, of course), the results from these clinical trials would have been encouraging enough that it would have qualified for further development. In other words, research suggests the low glycemic diet is as effective as some drugs would be.
“I think this is very important because, oftentimes, diet (as a treatment or prevention plan) really only gets lip service, because the effects of diet are usually small compared to taking a drug that can just hammer the risk factor down” explained John Sievenpiper, associate professor at the University of Toronto’s Temerty Faculty of Medicine. “Whereas, this is actually showing that you can get a ‘druglike’ effect from a diet.”
And with no list of off-putting possible side effects like the ones we see on TV advertisements. Instead, the side effects were weight loss and lowered cholesterol, inflammation and blood pressure.
Despite all of this, the GI diet often gets less attention than a number of other diets touted as good for our metabolic health, be they low fat, plant-based or low sodium. Perhaps because it’s a relative newcomer to the diet scene. Only 40 years have passed since Dr. David Jenkins, a professor in the U of T’s Faculty of Medicine, published the “glycemic index of foods,” the research that would be the foundation for the low glycemic index diet.
Four decades might sound like a long time, but consider this: the carnivore diet turned 165 last year. There are a lot of diets — not all of them good — out there. And they’re all competing for space in a crowded market.
The idea behind the GI diet is simple. Different foods have different effects on our blood sugar levels after we eat. Foods that have a high GI (70 or higher) cause our blood sugar to spike higher (and more quickly), so we’re not supposed to eat much of the foods in this category, which includes sugary breakfast cereals, white rice and birthday cake. You’ll find pineapple, parsnips and cornmeal in the medium GI category (56 to 69), so patients are advised to eat a moderate quantity of foods like this, since they cause more moderate increases in blood sugar.
Finally, there are the low GI foods (55 and under, just like the speed limit), such as apples, sourdough bread and sweet potato. We should strive for as many of these foods as possible, so stock up on barley, something of a superfood by GI standards, thanks to it weighing in at 28, making it the lowest of the low in the grains category.
Over the years, the low GI diet has been criticized on a number of fronts, but the most common critique is that it can appear complicated, because there are a lot of different foods to remember across categories. That said, the research subjects who test-drove the GI diet for the study didn’t have too much trouble, said Laura Chiavaroli, lead author of the paper.
“The design of most of these studies was just dietary advice,” said Chiavaroli, post-doctoral researcher in the department of nutritional sciences in the Temerty Faculty of Medicine. “So you’re just given a sheet that says eat these low GI foods versus those high GI foods, and they select certain ones (like barley) as their core carbohydrate foods, as opposed to the other ones (like white bread), most of which are found in a more standard diet.”
With this in mind, it would be a lot easier for everyone if the specific numbers were more accessible, and the researchers say the best way to do that would be to have the GI levels of foods added to standard nutritional labels.
“You can tell people to eat a low glycemic index diet, but then they go to the supermarket and don’t know how to make their decisions,” said Sievenpiper. “It becomes tricky when they don’t have that guide in front of them since we don’t have it on the food label, which is something we’ve been advocating for.”
Sievenpiper hopes that Health Canada will eventually add GI levels to labels. In the meantime, check out Diabetes Canada’s food guide.
And, when in doubt, barley is the answer. Eat enough and you might even lose weight (by accident).