I would not assume this is a “Keto” or “who does the cooking” issue.
If he has asked more than once or twice and won’t accept “no”, the issue might have deeper roots.
Remember, you are doing something successfully that he won’t (not can’t - won’t).
If your mood is better and you are focusing more on your personal appearance - you might be triggering him (consciously or subconsciously) into sabotaging your efforts. Maybe he just wants his “known quantity” wife back.
Of course, I have no idea if this fits your situation but, plenty of marriages break up when one half makes a big health move and the other couldn’t be bothered. If he sees that writing on the wall then (again consciously or subconsciously) he may cause a ruckus hoping to get back to status quo.
Similar to “Come to the gym with me?”
“No, but you’re not going to leave me here alone, right?”