How Gut Bacteria Drastically Affect Your Blood Sugar (But Not Your Weight)

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Sorta transcript:

A cool new study has just been published by researchers in Israel who found that when it comes to the food we eat and how it affects us,, there’s a lot we haven’t figured out yet.

You’re probably most familiar with blood sugar as it applies to people with diabetes, which is caused either by your pancreas not making enough insulin (Type I), or by your cells not responding to insulin correctly because of obesity, inactivity, poor diet, and a bit of genetics (Type II). This means that people with diabetes struggle with blood sugar getting too high or too low, which can result in seizures and coma if left untreated.

The food you eat has a huge impact on your blood sugar, which is why people with diabetes need to know how their blood sugar will change when they eat certain foods. Past research has led us to create the glycemic index, a measure of just that. White bread, for instance, is considered a high GI food because it causes the blood sugar to spike. Kidney beans would be an example of a low GI food.

This new research turns that knowledge around, though, showing that different foods can have dramatically different results on individuals’ blood sugar levels. The study measured the levels of 800 people who were either healthy or pre-diabetic, and had them eat one consistent premade meal a day. They also took fecal samples so they could measure gut bacteria. Gross, but fascinating!

Sure enough, different gut bacteria reacted in different ways to the various foods, to the point that some people had a bigger blood sugar increase after eating sushi compared to eating ice cream.

The good news is that this means that in the future, doctors will be better able to personalize diet recommendations for diabetic and pre-diabetic patients. The bad news is that those patients are probably going to have to poop in a jar to make that happen.

What this research doesn’t tell us, contrary to some of the reports I’ve seen in both mainstream media and in blogs, is how this affects weight loss and weight gain. Blood sugar is obviously related to weight, as we see with obese people who are much more likely to develop Type II diabetes. But past research hasn’t shown any link between low glycemic diets (remember Atkins?) and improved weight loss. That might be related to the fact that those low glycemic diets may not have actually been that low for some patients with specific kinds of gut bacteria, but we just don’t know. Now that we do know how much gut bacteria can affect blood sugar, we can see what all this means for weight loss.

In the meanwhile, I’m sorry to say, if you want to lose weight you’re going to have to do it the only way anyone has proven works: eat less. Move more.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor. Twitter @rebeccawatson Mastodon mstdn.social/@rebeccawatson Instagram @actuallyrebeccawatson TikTok @actuallyrebeccawatson YouTube @rebeccawatson BlueSky @rebeccawatson.bsky.social

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  1. Well, you can lose weight surgically. Or by having a severe digestive disorder. Or some kind of bullemia. I can’t say those are as healthy as diet and exercise, but they do work.

  2. Great! Now we can claim exceptionalism and blame our gut bacteria!
    Stand by for a whole bunch of special pleading.

    Seriously though, your final comment is right on the money. Can I take this opportunity to thank you for your earlier (March 2015) tip of aiming for a 500 calorie a day deficit?

    That made a huge difference to me personally. Probably saved my life in fact.

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