The body is like an auto. It needs:

1) energy (the Chinese call this Qi), to move the blood and fluids. This is like the energy provided by the generator.
2) blood and fluids to nourish the body and remove toxins. This is similar to the function of oil in a car.

So to create these two necessary functions, it would be best to:

1) Clean water.
2) Clean air and good breathing.
3) Lots of nice clean vegetables.
4) A reasonable amount of clean fruits (not juices – too concentrated).
5) A good amount of whole grains.
6) Some small amounts of fish and poultry to taste.
7) Occasional meats if you like.
Nothing cold and very little raw (obstructs digestive process)
9) Very small amounts of non-water liquids.
10) Avoid processed foods especially sugars and dairy.

All this provides the raw material for creating healthy energy in the body. However, the body has to be well oiled so that it can digest and assimilate. That means getting plenty of movement in life (including sunlight) and avoid obstructions in the body, e.g. fat, stagnation caused by sitting around, stress related stagnation (clench your fist to understand what I mean), constrictions within the body caused by muscle building exercises, such as weight lifting.

A well functioning body can live quite a long time without any outside assistance. I do yoga, Tai Chi, Qigong daily as well as eat well, self-massage by body, and get plenty of sun and energy from walking around.