A serious explanation would be just as Randman said...he was fed more.
The reasoning might be more determinable if we know more about the circumstances. Back during the colonial period in Europe. Many of the countries abided by the Rules of War, whereby an opposing military commander was afforded the respect such a commander had earned. He would usually be placed in a relatively nice cell, be fed well, and even given the opportunity to write letters home. The men weren't treated as well, but even they were given the necessities of life. Quite often, all POWs were released as part of the accords signed to end a war.