American funnyman Steve Martin has laughed off critics who claim he looks overweight in new movie SHOPGIRL - he insists he lost nine kilograms (20 pounds) before shooting the comedy thanks to a self-designed diet.

US entertainment writers have described the ROXANNE actor as "old" and "puffy" in their film reviews - which also stars CLAIRE DANES - but Martin remains unfazed because he actually discarded so much fat, he then had to put weight on.

He tells the New York Daily News, "I lost 20 pounds - actually, I lost 25 pounds, but then I gained 5 back because I was too skinny.

"I didn't change what I ate, I just started eating smaller portions. And I cut out bread - that's the real killer, because I was reaching in and eating half a loaf before dinner arrived.

"All you have to do is that, and then you can drink all you want."