Bodyweight, and body fat are mainly determined by diet. Your body composition is a result of what you consume.; you are what your eat. yeah, I know, most guys will say they are just a big pussy... (hahaha) Well, man or lady cannot live on pussy alone, you need some bread to soak up the juices.
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Our bodies are designed to consume whole foods, not processed foods. So, the more you eat whole foods, and the less of the processed foods your body with begin to reflect to what you are consuming. Another thing is portion control, food is an energy resource to refuel your body, you only need to consume what your will use until the next refueling, Otherwise the excess energy consumed gets stored away in fat cells. You can never completely get rid of fat cells, unless you physically remove them from your body they only grow and shrink. So, you want your fat cells to be at miniminal size possible, not storing extra fuel (fat cells) on the body as a fuel resource. You wouldn't phycially carry around an extra 10 gallons of fuel for your vehicle, you would only feed your vehicle what it can use. So why in your right mind would carry the extra fuel [fat] on your body in true reality.
You want to have some percentage of body fat, just not more than what is really needed. Everyone has a percentage of fat pad, it's just a matter how sloppy is it.