Mind controls the body. If mind is disturbed it reflects in the body. The disturbance in mind (more Happiness or Sadness due to love affair or love failure ) induces different Harmon levels from glands which results in weight loss or increase. You can see such cases in real life in society.
Whats the Marmam behind Yogi?
Yogi is a person who is able to control his mind and body. Yogi can also undergo such disturbance like more happiness and sadness in mind but as he is able to control the mind and thereby the glands it will not reflect in the body as weight loss or increase.
Can Energy be conserved being a Yogi?
Yogi is able to control his emotions and be truly a emotionless being and expose the required level of emotions to people with control and without involvement. This is the mechanism which conserves energy for a Yogi. Yogi can live life with minimal food intake. People generally become emotional and get involved in the emotions like anger and lust and they waste energy.
Can a Yogi do miraculous things?
Yes. He is knowledgeable enough to know how mind works and able to control his Conscious mind. The data in the Subconscious mind has no impact on the thoughts produced in the Conscious mind for a Yogi.
Can a Yogi able to control his breath and be poised at any circumstances?
Yes. Yogi can virtually have infinite spiritual energy and breath control and mind control to confront any person who may be extremely good or bad.