Actually, I think you may be onto something with HealthyMenu.net - This name has great potential and would be stellar as a dot com. Now, weve obviously pointed out the biggest issue, its a .net. But beyond that it definetly has potential. Had it been avail, I might have grabbed it. This is definetly worthy of a mini-site or even development.
HealthyWorkout on the other hand doesnt quite make sense. Although yes, there are unhealthy workouts (pushing yourself too hard, ect) This isnt a natural phrase that rolls of the tongue and would require substantial branding to be valueable.
1 out of 2 aint bad
But, I would also recommend sticking with dot coms, you'll find even a "poorer" dot com, will do better than a "better" dot net.
Justin