Your gut bacteria don’t change how much waste they produce overall, but they do change what kinds of waste chemicals—like butyrate and lactate—are made, and this mix is different for everyone...

What you eat—especially fiber and complex carbs—mostly decides how much gut fermentation happens, and eating more of these carbs can boost fermentation by up to five times compared to a standard Western diet. The types of gut bacteria you have don’t really change the overall amount.

The gut bacteria in people eating lots of fiber can provide up to 12% of their daily energy, while those on a typical Western diet get only 2%–5% from their gut bugs — so what you eat changes how much energy you get from your microbiome.

What you eat overall—like veggies, meat, or carbs—is probably what’s really changing your gut bacteria, not the sugar-free sweeteners in your diet.

The mix of bacteria in your gut might be connected to conditions like obesity and diabetes, and certain types of bacteria could be tied to storing more fat and how your body handles sugar.