Microbiome Transplant Evidence

Lean-twin bacteria could reverse weight gain in mice — but only when the mice ate high-fiber diets. Without fiber, the beneficial bacteria could not establish stable populations, and the weight-loss effect faded within weeks. The microbes need the right food to take hold.

Bacteria can drive weight changes independent of how much you eat. Fiber lets beneficial species outcompete obesity-linked ones.

That makes the microbiome a metabolic mediator — a layer between what you eat and what your body ends up storing.