If you lose weight by starving yourself I can believe it could adversely affect your game.
If you lose weight because you worked it off through cardio, strength training (lighter weight & more reps) and diet, then how can that be a negative? I will always believe that over the course of a long winter season that someone who is physically fit has an advantage over "Jabba the Hutt".
Maybe if all you do is throw 3 games a week you can get by for awhile, but eventually other weight related health problems such as diabetes or joint issues could catch up to you and affect your performance.
Since dropping some weight, I have zero joint pain now and my border line BP is mostly normal now - 120/70. I'm one of those healthy fat people when it comes to blood work too. Everything is normal.
I went from over 20 years of martial arts to zero since 2000. The last 8 years of MA was 6 days a week, twice a day on MWF, sundays off. My goal is to slowly get back into it and fit my gi again lol. My obi (belt) looks like a bow tie around my waist.
I got the TRX that I'll use between patients/exams in my office. I don't plan to bulk up - long and light reps. also, I have a new proform treadmill in the garage. I just need my health...I have a one yr old daughter who I want to bowl with when I am in my mid 60's lol....