Am i over reacting?

Natalie
This may be my boyfriend and I first fight. We've been dating almost three months now and we always jokingly talk about working out. He does it, I don't. I'm at a reasonable weight. 150 lbs standing 5'6. I told him I'm not working out until tennis starts and that I'm comfortable with myself. Never has he suggested I needed to lose weight. But on this argument he threw in "to gain muscle and look better." That ticked me off. So I've been mad at him for about an hour now. I don't want to be mad but I am. Am I over reacting?