If two people eat similar foods and live similar lives, why does one gain weight more easily?
Calories, movement, and sleep all matter and are the biggest factors for a healthy metabolism and body fat.
But there’s another factor quietly influencing the entire equation: your gut microbiome… the trillions of microbes living in your digestive tract.
Here’s what’s funny though: the microbiome doesn’t “force” weight gain. Instead, it can influence the signals and efficiency that make weight gain or unhealthy fat storage more likely for some people.
1) Some microbiomes may extract more energy from the same food
One of the early landmark findings in microbiome science was that the gut microbiome in obesity can have a different “metabolic capacity;” an increased ability to harvest energy from diet in animal models. In a classic Nature journal, transferring an “obese microbiota” into germ-free mice led to greater increases in body fat compared to mice colonized with a “lean microbiota.”
That doesn’t prove the same thing happens directly in humans, but it’s a strong indicator that microbial communities can influence energy balance.
2) Microbes can influence hunger and fullness signals
Your gut bacteria ferment dietary fiber into short-chain fatty acids (SCFAs) like acetate, propionate, and butyrate. Those metabolites don’t just stay in the gut: they can interact with metabolism and appetite pathways.
For example, experimental physiology research shows SCFAs can stimulate the gut to secrete GLP-1 (and to a lesser extent PYY), hormones involved in appetite regulation and blood sugar control. As long as you’re not living under a rock, you have heard of GLP-1 and its impact on reaching a healthy weight.
More broadly, recent reviews describe multiple microbiome pathways that can influence appetite regulation through gut hormones and the gut–brain axis.
In short: when the microbiome is supported by fiber-rich foods, people often report better satiety and steadier energy, which makes overeating less likely.
3) Modern diet exposures can shift the microbiome
A fiber-poor, ultra-processed diet reduces the raw material your beneficial microbes thrive on. Reviews describe how dietary fiber is fermented into beneficial metabolites (like SCFAs) and how fiber intake patterns relate to microbial ecology and metabolic health.
And some non-food exposures may matter too. For example, a Nature study reported that certain artificial sweeteners altered the microbiome and were linked to glucose intolerance in experimental settings.
What Steps to Take for Your Healthy Weight Goals
We’ve got some clear actions for you to consider:
Prioritize sleep + movement (both influence appetite and glucose control, which feeds back into the microbiome).
Aim for fiber diversity (legumes, vegetables, berries, nuts/seeds, whole grains if tolerated).
Add fermented foods if you tolerate them (yogurt/kefir, kimchi, sauerkraut).
Reduce ultra-processed foods (they often displace the fiber your microbes need).
Consider adding this at-home recipe to your daily food and drink: To really see this recipe in action, you should watch this video about Meghan See, who lost a crazy amount of weight with this change in her daily life. She was even featured on Jada Pinkett Smith’s talk show Red Table Talk to talk about her incredible transformation.
Click the video image above to learn more about Meghan’s at-home recipe.
