How many carbs per day for weight training to lose belly fat?

I’m confused. When bodybuilding, you should have lots of carbs since building muscles require a lot of energy (more than 40 g of carbs). Muscles lose fat and has great metabolic rate than fat. However, people suggest low carb diet in order to lose fat which contradicts weight training. What’s going on? How many carbs is needed to lose fat when you do weight training?