Well, more accurately, digestive health and the bacteria within you play a vital role in how easy or difficult health and fitness is. Here’s yet another study showing how microbes influence obesity:
I find it really interesting how much cultural beliefs prevent people from flourishing. Thirty years ago it might’ve been considered quackery to believe that an individual might need to abstain from dairy or grain proteins or certain foods which perpetuate for them a constant signal to grow fatter.
But now we know better. Our gut flora play a huge role. And when you are getting the feedback that you can no longer tolerate a whole category of food... well... maybe stop having it. Maybe fast for a bit. And then, maybe try to restore great digestion. It can be done. It has been done.
Even in people with Crohn’s or Celiac, they are able to get well, returning their digestive tract to a healthy functioning routine, consistency, etc. The many pathologies which “inexplicably” plague our modern world are not so inexplicable. They are perfectly explainable when you consider the integral role of digestion.