I'd consider some of the high cal Myoplex or similar immediately after your cycling workout. 2% chock milk blended w banana and peanut better will also work.

I used to have your problem years ago. Then I took up smoking, booze, rich food and odd hours. I soon developed the opposite problem. Now, cycling, moderation, and a good nutrition plan have me on the way back to fitness.

When you get older, just don't forget your "fighting weight" is low. i.e, don't ever get sick of being scrawny and try to become a 180 lb bruiser. I tried that - it didn't work long term and just gave me joint problems short term.