Whether it´s a good idea to have a little extra fat or not depends on many factors (like weightclass, natural or not, genetics etc.).
But there are also chubby guys in the middle weightclasses.
Usually they wouldn´t be really obese but Martirosyan (spelled correctly?) carries a few extra pounds and still became world champion in the 77 kg class while his rival Lu Xiaojun could enter a bodybuilding comp any given day.
Also there is one guy in my lifting club who used to weigh 7 kg more (he was really fat) and produce about 80-90 relative points. Saturday, weighing 81 kg, he could only achieve 60 pts I believe. His weight loss may not be the only reason for that but still I´d say that it didn´t do him much good.
210 kg SQ, 135 kg Bench, 260 kg DL
Long Term Goals:
@ 75 kg: SQ - 252,5 kg, SQ w/ Wraps - 282,5 kg, DL - 307,5 kg, Total (w/o Wraps) - 710, Total (w/ Wraps) 712,5 kg
@ 82,5 kg: SQ - 275 kg, SQ w/ Wraps - 277,5 kg, Total (w/ and w/o Wraps) - 772,5 kg
Team Insanity - The Laws of Physics are Merely a Suggestion