Both Knapp and Cruz say that when your gut bacteria is imbalanced and you're lacking good bacteria, like certain strains of lactobacilli (which has been proven to help lose belly fat, in a study published in the Journal of Functional Foods), the result can be an influx in belly fat and a higher weight. Cruz recommends her patients make sure they are providing an optimal gut ecosystem by eating fermented foods (like Greek yoghurt) and a diet that's primarily plant-based, while Knapp suggests clients take a daily probiotic and follow a low-sugar diet to keep gut balance in check.