FEEDING TIME & METABOLIC DISEASE
Human testing is limited in the area of microbiome research, however, it's fairly well established that consistent 'after dark, or night-time feeding' will lead to metabolic issues and weight gain.
WHAT you eat is not the only thing that matters. WHEN you eat also turns out to be of utmost importance. In addition to the timing of feeding having an influence on the overall composition & diversity of the gut bacteria, it may also be involved in controlling - through its effect on hormone levels - gastrointestinal inflammation.
As approximately 75% of the human immune system is located within the alimentary canal, inflammation in the gut also ties closely into host immune function. Artificial light, irregular sleep patters, arrhythmic feeding, shift work, & jet lag have all exacerbated complications with human immune function in the modern world.
Whether or not microbial diversity supported by rhythmic feeding on 'high quality REAL food' is directly related to a 'sufficiently strong' immune system, remains to be seen, but, my completely amateur sense is that scientists in this field will soon discover, that indeed it is.
This is based on my own experience with a high fiber, '6-9 cups of veggies per day' paleo diet, daily prebiotic consumption, as well as my regimented sleeping & eating patterns.
Future research in the field should be exciting. Several websites, such as caloriesproper.com, come highly recommended for consistent updates in the area of clearly explaining the importance of circadian rhythms, and the gut microbiota.