..."Honey! I see you ate all my low carb food. That's wonderful! It must mean that you want to eat like I do and join me in my weight loss efforts. Great...I'll clean out the fridge and cupboards of all the high carb stuff you've been eating right now so neither of us will be tempted to cheat and I'll make sure I make enough of everything for both of us. What? You don't want to be on my diet???? WELL THEN STOP EATING MY FOOD!!!!!!"

On a more serious note....you could try labeling "your" food as yours and let him know not to eat anything with your name on it because you didn't make enough for him AND you to both eat it. Or....you could just make twice as much knowing that he's likely to dig into it no matter what you say. Just a thought....