Is my rabbit over weight?

I have three rabbits and two off them are hopping around playing happily. While my other rabbit (Toffe) Sits their. He will move when he want to . Also when people look at my rabbits they always say that a fat rabbit . He's a tortes Shell rabbit. He eat lots more then the other rabbits he eat a full bowl of dry food a day . And a bit of veg and fruit . While the other rabbits eat more vegetables then dry food . Is that dry food making him fat? Or is it his fur thats making him look fat? Please let me know because if he is I will put him on a diet. Also shpuld I put him on a diet? :) x