The goal of this clinical trial is to learn about the effects of avocado consumption on gastrointestinal health in adults with overweight and obesity. The main questions is aims to answer are: How does avocado consumption affect the gut microbiome? How does avocado consumption affect thinking? Are there connections between the microbiome and cognition? Participants will be asked to eat provided meals with and without avocados for three 4-week periods. At the end of each 4-week period, participants will be asked to provide stool samples and complete computer games that assess thinking and memory.