Part 2: The gut clue behind “naturally thin” people

I wanted to follow up on the email I sent Thursday with a question:

Have you ever noticed how some people seem to eat whatever they want and not gain weight?

We all know someone who eats the same foods we do, but their body responds completely differently. Why is that?

Do these people keep their weight in check through intense gym routines? Did they win the genetic lottery? Is it plain old luck? Well…

While food choices absolutely matter (plant-based eating — yay!), the research I found suggested there’s something else going on behind the scenes that most people don’t know about.

Something that finally explains why two people can eat the same food, do the same exercise, sleep the same hours… and one gains weight, while the other stays lean.

So what is it? Believe it or not, it’s your gut bacteria.

I realize that might sound kind of out there. 

But this is where the research gets really interesting. Scientists have looked at this in more than one study.

In the first study, scientists at Washington University in St. Louis, one of the world’s leading microbiome research centres, took mice that had been raised germ-free, meaning they had no gut bacteria at all.

Then they transferred gut bacteria from obese mice into them. Within weeks, those germ-free mice gained significantly more body fat.

These mice were eating the same food as before… but now they were gaining lots of extra weight. The only difference was their gut bacteria.

But the results were even more surprising in a human study.

A few years later, researchers from the same lab looked at human twins.

In each twin pair, one twin was lean and the other was obese. They had similar childhoods, similar early environments, and as twins, they shared many of the same genes.

But their weight and body composition were dramatically different.

The researchers transferred gut bacteria from each twin into separate groups of germ-free mice. And again, the results were hard to ignore.

The mice that received bacteria from the lean twin stayed lean. 

The mice that received bacteria from the obese twin gained more body fat.

You know the expression, “You are what you eat?”

These studies show that it’s more accurate to say, “You are what your gut bacteria do with what you eat.” Especially when it comes to your weight.

Some bacteria are better at extracting energy from food. Some influence inflammation. Some affect the signals involved in metabolism, blood sugar, and fat storage.

So when two people eat the same meal and get very different results, the difference may not come down to discipline, willpower, or even genes.

It may come down, at least in part, to what their gut bacteria do with that food.

I find this so encouraging!

Because I’ve heard from so many women who are eating well, choosing healthy foods, doing their best… and still feeling like their body isn’t responding the way it should.

And it’s not their fault. It could all be tied to their gut bacteria.

Of course, that raises the next question:

Can you change your gut bacteria so it’s easier to reach and maintain a healthy weight?

That’s what I’ll share on Monday, including a common gut health mistake that may be tripping you up without you even realizing it.

P.S. — The two studies I mentioned are Ridaura et al., published in Science, and Turnbaugh et al., published in Nature. 

Both are peer-reviewed and still widely cited in microbiome research.