Here are my top 10 first principles for human health:
Real Food - cooked at home - not restaurant food
Movement - move as often as possible, daily.
Nature - get outside as often as possible and listen to sights, sounds, etc. Detach from your devices
Sunlight - you need it.
Community - spend time with people you love as often as possible
Avoid consistent doses of poison - a little poison here and there might even be beneficial. Still, since our environment is overloaded with stressors, we need to make it our goal to avoid them as much as possible. This includes chemicals, odors, artificial foods, seed oils, sugar, etc.
Negativity is killer - you're not going to be perfect, nor are the people around you, but making it your focus to be as positive as possible is your best strategy for long-term health and well-being. Since so much of our biology and environment focuses on the negative, you have to fight to maintain positivity constantly.
Sleep 8 hours a night in a pitch-black room
Stress mitigation - do everything you can to mitigate stress, especially that nagging chronic stress that has become an epidemic in modern human life.
Play - play, laugh, have fun.
This shortlist represents about 95% of what you need for optimal health, weight loss, and longevity.