Gosh. What an abso-lute ARSE.
Lazy-arsed selfish tosser!
IF he got his arse moving doing some housework it might help him with the non-lapsing back into fatness, hmm?
IF he is going to the gym that much and taking dodgy supplements, it is unhealthily obsessional and he is either on steroids or has become an adrenaline junkie, neither of which are good for anyone.
As for you being too skinny and he wants you to work out, WTF?? You don't need to cut out carbs if you're too skinny, you'll waste into nothing!
And I can tell you now that if DH tried that bollocks of "you might as well be up to start the housework and remind me to go to the gym" at 5:30 in the morning, I'd have got up all right - once! And booted him out the door, down whatever steps were available and chucked his stuff after him!!
Doesn't sound as though he's had much of a kick up the arse to me. What you need to do is lay down the law about how things are going to be - as in, which household tasks he is going to share and when, how much he is going to do to help with the DC and when, and he can still go to the gym 3 times a week which is just about normal for most people before it moves into obsessional.
"No improvement in a week" - well you've left yourself a bit wide open with that - all he needs to do is a couple of things and then bugger all else and it would still be "an improvement" on what he's been like - so he could argue that he did better. You really do need to set out exACTly what you want from him and make him stick to it from day 1 - no "building up" to it, start high and keep it up there or he leaves.
Good luck!