Some advance studies suggest that the gut bacteria control and maintain our immune system. And our health. Feed the gut bacteria properly, and they will take care of you.
It's like farming now. Raise the proper soil bacteria, and forget crop fertilization. Activated sludge was a first use of such a principle. Now farming is starting to use it. A proper biomass environment. Maybe in the future, we take a weekly gut test, and the results recommend a selection for next week's diet. Instead of scales.