One who creates a small defect in the body creates a great defect in the soul (Maggid of Mezritch ).
A student spied the great Hillel leaving his academy. He approached the Sage and asked him where he was going. "I am going to do a mitzvah for someone poor and forsaken," Hillel answered. Noting his student's bewilderment, he then explained: "I am going to feed my body. It is totally dependent upon me to look after it."
If someone gives us an object for safekeeping, we have a responsibility to look after it and cannot be derelict in its care. Likewise, our bodies have been entrusted to us, and we have a full obligation to care properly for them.
Too many of us violate our trust by taking unnecessary risks or doing things which are detrimental to our bodies, such as smoking, overeating, or abusing alcohol and drugs. Is it not strange that one who would never think of drinking a non-diet soft drink might not have the least hesitance in smoking a cigarette, even though the harmful effects of smoking are now established beyond a shadow of a doubt?
A Chassidic master observed one of his followers who looked lean and weak. On inquiring, he learned that this man was fasting frequently to atone for his sins. He then told him: "First you set out to ruin your soul, and having achieved this, you are now out to ruin your body as well."