gaining weight

[latefordinner]

I've been about 5'10", 120lbs for 10 years now. I literally cannot put on weight or muscle no matter what I do. I'm in decent shape - tend to bike about 50-100 miles a week just getting around town - but I think my skinniness has a negative effect on my health generally.

I've tried powders, eating 4000 calories a day, working out, cutting out all caffeine for months at a time, eating mostly meat, eating no meat, eating a lot, only eating one meal a day one day and then 4 or 5 the next to slow down my metabolism - NOTHING

even when I was living in Ireland and drinking a 6 pack+ of beer most nights and eating like [censored] I gained a whopping total of 2 pounds.

I don't want to be giant, but I think 140 or so would be a much more reasonable weight.

Any suggestions?