I'm not sure myself - but I think it's minimal, especially if you eat right. You should be eating a meal high in carbs and moderate in protein 90 minutes before you work out, either doing cardio or weight lifting. If you're going for an extended cardio session (like a marathon, or a personal record breaker), keep your glucose up by drinking a sports drink, like Gatorade, or just normal water mixed with a reasonable amount of sugar. Afterwards, grab a carb+protein shake.
I can't stress enough about the post-nutrition part. The (simple) carbs are actually more important than the protein, because they cause an insulin reaction that drives the protein into your muscle to help promote muscle synthesis. There are mixes out there for post-workout drinks (like Surge, I don't use it myself, but I may sometime soon), or you could mix the whey powder of your choice with maltodextrose/dextrose powder.
About your friend... I think that's what we call a skinny fat person

What's his nutrition like? If he's eating fast food, eating too much, eating at the wrong time of the day or not eating frequently enough, then that might explain the pauch.