Things went well as long as mind was a servant of the body. Then it became the master and dictator of body. The mind started posing itself as a scientist and started questioning everything that were well-tested over centuries. It came up weird things such proteins, vitamins etc, but it forgot that what mattered was the big picture.
Body suffered silently as it lost it's most critical servant whom it trained over millennia.
It was enough to know that water flows down the slope, apple falls to ground, Sun goes around the Earth and life follows a rythm of seasons. Human life never needed Kepler's laws, relativity, quantum physics, computers, cars or sugar.
It's not too late. Listen to your instincts and body signals. Live on a farm (farm means crops and gardens, not just animals). Eat like your ancestors did. Eat less, eat varied food, more of greens and grains, mostly raw with a bit of cooking or heating.
That's really not true at all. For example, rabbits love sweet stuff like fruit and will readily kill themselves by eating too much, which causes their delicate hindgut fermenter digestive system to shut down.
Like humans, they simply aren't adapted to conditions where they have unlimited sugary food like fruit, so they will eat too much when given the opportunity.