The Hitch star tipped the scales at 302 pounds (137 kilograms) last year (10), and decided to get serious about slimming down for his health.
He says, "It got to a point where I hit my all time high... I got on the scale and it read 290 pounds (131.5 kilograms). Not good, not good at all. I realised I'm only 10 pounds (4.5 kilograms) away from 300 (136 kilograms). I got to 302."
And James - who is expecting his third baby with his actress wife Steffiana de la Cruz later this year (11) - has already shed 42 pounds (19 kilograms).
He says, "Now I'm down to about 260 (kilograms)... I want to be there for them (my family). That's important."
De la Cruz, 35, debuted what appeared to be a baby bump in a tight fitting ensemble when the couple arrived at the Chicago, Illinois premiere of the actor's new film The Dilemma last Thursday (06Jan11).
And James, 45, confirmed he had another bundle "on the way" on America's The Today Show on Wednesday (12Jan11).
The couple is already parents to daughters Shea Joelle, three, and Sienna-Marie, five, and the new addition is due later this year (11).