I can't put on weight. Through what I've learnt from Dr.Lam regarding my AF, my understanding is that the metabolic process becomes compromised. This leads to a catabolic state where the body breaks down it's own lean muscle tissue to provide energy. I've experienced weight loss in the last few weeks as my AF has worsened. Digestive processes slow down due to the body being in fight or flight all the time. I have had loose stools for ages as though food passes through me to quickly without being digested properly.