Good advice from everyone and I echo their sentiments.
You're doing this for you, be selfish. Tell him exactly why you are doing this, tell him how the extra weight makes you unhappy and if he doesn't like it then he can lump it! Show him how determined you are by going out for the meal and don't eat, sip a delicious sparkling water, he'll soon get the message.
My OH hated the first week, he said I'd become a complete psycho bore. All because I wouldn't be eating my usual weekend Chinese and getting peed on vodka then dancing round the lounge! When the first week passed and I lost 14lb and I started to feel better he slowly changed the attitude. Now by the second week and another 9lb gone he thinks I'm the best thing since slice bread. It may have something to do with me bouncing off the walls and having the energy of a 2 year old! Although it's most probably the fact that I found my long lost mojo in a LT shake. Before he went to work this afternoon he said that he's worried as I might want to go pubbing and clubbing when I lose more weight, and that I may meet a younger model and run away with him ha! He said all this was a joke but I think it was a joke with a jag. He would probably prefer me fat and miserable, that way he knows he has no competition haha!