Excerpt from Exposition of the Christian Faith:

Truly, Christ won salvation for us, not by luxury but by fasting. Moreover, it was not to obtain favour for Himself, but to instruct us, that He fasted. Nor yet did He hunger because He was overcome by the weakness of the body, but by His hunger He proved that He had verily taken upon Himself a body; that so He might teach us that He had taken not only our body, but also the weaknesses of that body, even as it is written: "Surely He hath taken our infirmities and borne our sicknesses."

ST. AMBROSE'S EXPOSITION OF THE CHRISTIAN FAITH, BOOK III,CHAPTER I, v. 6.