In Phase B, a subset of the participants, which will be chosen by random drawing from a box, will switch to an all-Soylent diet. During this phase, they will consume five bottles of Soylent 2.0 daily for four days (one for breakfast, two for lunch, and two for dinner), fully meeting a 2000kcal diet and all recommended nutritional daily values. The remaining participants will retain their regular diets for four days. These individuals act as a control for the daily variance of microbiome fluctuations.