I have very defined abs but I eat junk and have never worked out a day in my life?

So I'm 17, and I hate to admit but I have a very unhealthy diet. I drink sodas regularly, eat chips and ice cream etc. I've never worked out a day in my life. I don't even do very active sports. But, I have very very visible abs! I'm a teenage girl and have more defined abs than my guy friends in their twenties who work out EVERYDAY!!! I'm not complaining lol, just confused as to why. Is it because I have an extremely fast metabolism and my fat % is super low? I just don't know. For example my abs are so defined you can set a pencil in the creases and it will stay for the most part lol

for all of you who think I'm trolling this is 100% real. All of my friends are equally as confused. Can someone shed some light?
What the heck, how?
This is normal.
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I have very defined abs but I eat junk and have never worked out a day in my life?
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