I posted in another forum on this topic and it may help you out too:
You should not be loosing strength when you are dieting, you can’t flex fat and unless you have a huge gut and are wearing a bench shirt the leverage advantage to being fat would be miniscule. Make sure you are getting enough protein when you diet. I agree that BCAA’s are a good addition. Most important look at your benching mechanics (the post link I provided should shed some light on this). Hope this helps.