Turns out people might have very different blood sugar responses to the exact same foods, according to exciting new research published in Cell. That means that the common practice of ranking the "best" diets for weight loss (and all that advice to choose low-glycemic foods) could be misguided.
How could doctors and nutritionists be so off-mark on blood sugar science? Well, for decades, experts have used the Glycemic Index (GI) to determine how much a certain food will raise your blood sugar. The thinking has always been that the higher a food's GI, the more your blood sugar spikes after you eat it, causing your body to release insulin, otherwise known as the "fat storing" hormone. High blood sugar is also linked with obesity in previous research.
While this has been commonplace nutrition doctrine for years, researchers at the Weizmann Institute of Science in Israel wanted to test the theory that everyone's blood sugar response to foods was the same, so they recruited 800 volunteers and tracked their blood sugar constantly for one full week. Participants had to record all their meals, too, including a few standardized breakfasts that were the same for everyone.
The researchers found that the GI "standard" wasn't very standard at all: Different people had dramatically different blood sugar responses to the exact same foods, even those foods considered healthy. For example, researchers found that tomatoes, which are extremely low on the GI scale, made the blood sugar of one obese woman in the study go through the roof. That's right: A "healthy" low-sugar, low-calorie food could have been causing her to gain weight.
How could this be? Researchers suspect gut bacteria might be behind the highly individualized responses, especially as growing evidence suggests that these bugs play a big role in diabetes and obesity. (Learn how to hack your gut bacteria for easier-than-ever weight loss.)
So what does this all mean for you? For starters, it can help explain why one diet doesn't work for everyone—and why, if you suspect a food might be causing you to gain weight, there is a possibility that it could be. While this kind of personalized nutrition research is still in its early days, you can get more individualized nutrition advice by seeing a registered dietitian. In the meantime, you may want to try trusting your gut—literally—when it comes to which foods make you gain or lose.
