Thats not true Yeti. The right supplement/diet can actually speed up your metabolism – Protiemn vs Carbs is the simple calc here.
You’ll put on weight for two reasons while supplementing
a) If you’re using creatine, it retains water in your muscles
b) If you don’t do the exercise, you’ll get fat – supps contain calories too…..
People need to work out that hard exercise and your body needs fuel to recover, develop and repair. You dont have to use Supps but you should consider/alter your diet content and volume with this in mind.
ie – no fat on a bodybuilder but they eat X times more than a normal person.