Variability in Microbial Response to Dietary Fiber

The goal of this clinical trial is to understand varying in responses to different dietary patterns in healthy people who are getting a health screening colonoscopy. The main questions it aims to answer are: * What is the variability in the change of the microbes in the gut of (1) a provided diet that is high in fiber vs (2) a diet of the participant's choice. * What is the magnitude of fasting changes in glucose and lipids following the short-term, high-fiber feeding period and identify candidate predictive factors (short-chain fatty acids, BMI, sex, starting glucose level) for these changes Participants will be in one of two groups: 1. High-fiber diet group: These participants will have a series of measurements that include: blood biochemistries, body composition measured via DEXA, anthropometrics, surveys and questionnaires, and collection of fecal samples. 2. Normal diet group: These participants will eat a diet that is of their choosing (ad libitum) and will have a series of measurements that include: fecal samples, and questionnaires/surveys including food records.