The Brazilian has had a catalogue of injuries since he arrived at Old Trafford from Porto in 2007 and upon each return, he has often been criticised for being overweight.
However, the 25-year-old believes that he is now in the best shape possible.
"I've been training hard on the training pitch and in the gym, and working on my conditioning. I am pleased with how things are going and, whenever the manager needs me, I will be ready," he told Inside United.
"I have been doing more running, which has helped my fitness. The physios in Portugal have helped me a lot, as have all the coaches at United. I have also been working hard myself. I have built up the strength in my knee, worked hard in training.
"I have been eating well and sleeping well, while I have also been coming into training on my days off to do more work. It has really helped me and I feel great."
Anderson has featured for just four minutes in the Premier League so far this season.