"I have to say absolute credit to him," said manager Aidy Boothroyd, who thought the player was lacking motivation when he took over at Sixfields and refused to rule out selling him in the summer.
"He has lost two stone, he’s playing very well, he runs around and does all of the things that he was good at before, but has added to his game."
Akinfenwa will be a key man again as the Cobblers look to end a run of three straight defeats when they take on Torquay United on Saturday.
The Gulls have big local derbies coming up against Exeter City and Plymouth Argyle but manager Martin Ling said: "All I'm thinking about is my team to play Northampton, and the players are fully focused on that."