I too was always tired in the afternoon. I could not kep my eyes open at all! I felt like I had become lazy. I never thought that it could be related to cancer! Last year after becoming a double cancer survivor (breat & ovarian). My oncologist told me to avoid beef as it had the highest amount of hormones & antibiotics. I took it a step further and have eliminated many foods and am now following a clean eating bootcamp that has a meal replacement shake I take 1-2 times per day. I am no longer exhausted in the afternoon. I feel better and more confident that I am on the right path to good health.