Undoing health damage?

So, I just turned 20 years old and i'm wondering a few things about my health. So, for the past 4-6 years i have not been as healthy perhaps as i should have been. I eat basically OK, but definitely not well enough. I am overweight and have high cholesterol and triglycerides. I was wondering, at this age... show more So, I just turned 20 years old and i'm wondering a few things about my health. So, for the past 4-6 years i have not been as healthy perhaps as i should have been. I eat basically OK, but definitely not well enough. I am overweight and have high cholesterol and triglycerides. I was wondering, at this age can i reverse any damage that has been done to me through lifestyle change and daily/weekly exercise? I keep feeling like i've screwed myself up or something, but at my rather young age i feel like it may be reversible. Is it?
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