The Tsimane, who live in the Amazon Rain Forest in Bolivia, have no infrastructure or electricity and use a hunting/foraging system. Their diets consisted of mostly carbs from rice, corn, and plantains, and their meat does not go through any sort of processing. The combination of constantly remaining active and eating untouched foods high in fiber and micronutrients seems to keep them in pristine health.
Aside from food, the Tsimane exhibited consistent sleep patterns that revolved around light and a strong sense of community which has been proven to protect from heart disease. Perhaps the most surprising part of their health: parasites. All members had some kind of parasite that seemed to regulate their immune systems and protect their hearts. Going back to the basics seems to be the healthiest way to live.