Maharishi Charak has given a very scientific description of the importance of the stomach fire i.e. our appetite in our body thousands of years ago ......

Our lifespan,

Skin color (glow)

Body strength (shakti)

Health,

Enthusiasm,

Affirmation,

Prabha

Ojas, the brightness of the body and Prana i.e. life are the reasons for all this. Our appetite is the stomach fire. 

If the stomach fire is calm, then the person dies.

If the stomach fire is balanced, then one can enjoy a healthy and long life.

And if the stomach fire is weak or too sharp or if it is unbalanced, then the person falls ill.

Therefore, every person should eat a healthy diet in proportion to the season and according to his appetite.

So it can be understood that our sages were thinking about something much more than scientists.