I have really let myself go....really.

My husband thinks I need to exercise (and I agree with him), but he wants to see me jumping around like P90X or jogging or working out for 30+ minutes. I can't do it. I don't know how to explain to him that I don't have the physical stamina to do it. I think that watching The Biggest Loser in the past has given him unrealistic expectations. When I tried to commit to 15 minutes a day of moderate movement, he didn't think it was enough. Now I have just about given up. I think if I can get my eating under control and lose some weight then I can do more exercise. I think I will have more energy and won't have all this fat flopping around.

He is thin. He has no issues with food/carbs. He does not understand.

What should I say/do?