Why Does My Body Break Down Proteins Before Lipids?

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I learned that the body prefers carbs > lipids > proteins for energy.
When I job too long on an empty stomach, my sweat smells like ammonia; I found that this is due to the body breaking down proteins for energy.
I don't know why it doesn't break down lipids instead, since I have a lot of belly fat.
It's bad if it breaks down proteins for energy isn't it?
I'm trying to lose weight correctly.