Q: Why do some people say cardio in the morning on an empty stomach is better? Will it make me skinny?
A: First thing in the morning when you wake up your glycogen and blood sugar levels are depleted. You go 8hrs sleeping without food or drink. This meals that the fuel you will use for energy will come from fat stores.
CAUTION: I am not saying that I recommend exercising on an empty stomach. Because your glycogen and and blood sugar are so low you could risk passing out, getting a head ache or nausea. This is just an answer to why some people say cardio first thing before eating should be done.