A very non scientific but intuitive reason for the weight loss may be in major dietary changes. Studies show survey respondents usually gloss over excessive drinking (they're all "social") or gluttony (just some "snacks"). I can't recall a single fellow radiation patient in the waiting room talking about eating candy bars, or potato chips, or cookies or any sugary snack. Nor did they guzzle sodas and with the exception of myself, they gave up alcohol. Major calories not usually counted by people. Just speculation on a Sunday morning.
Of course I had given up all sugar years ago, and lost weight during TX, but expected it since I did not want or have a PEG.
But I used to eat a bag of potato chips at one setting and after IMRT had no desire to do so ever again.
Charm