A foundational diet should include at least these four factors that are agreed upon by all experts in this field, whether they lean toward low-fat, low-carb, paleo, vegan, Mediterranean, or other:

i. Emphasize/increase whole foods
ii. Emphasize/increase vegetables in particular (and specifically non-starchy vegetables)
iii. Minimize/avoid added sugars
iv. Minimize/avoid refined grains
https://www.reddit.com/r/loseit/comments/80rmtd/hi_im_professor_christopher_gardner_professor_of

Rather than taking supplements, experts recommend eating fermented foods (probiotics) to promote microbiome diversity and fibrous foods (prebiotics) to feed and sustain "good" bacteria in the gut."

"The influence of our microbiome extends far beyond the confines of the digestive system, reaching major body systems like the immune system, metabolism, and the central nervous system"
https://longevity.stanford.edu/lifestyle/2024/04/08/probiotics-prebiotics-and-postbiotics-what-are-they-and-why-are-they-important