3 weeks without food is nothing if he does not loose weight.
My lesser male was 817 grams at the beggining of breeding season (27th september 2012), and his last meal was on 17th of september 2012. And he just took his first mouse since then (16th of april 2013 - 762g at that moment), so he lost only 55 grams and locked over 25 times during this period .
He did great, even that he didn't eat at all during breeding season.
So just monitor his weight and he should be fine, unles there is something else going on, but mostly if something is wrong they loose weight .