Starvation, too much exercise, dizziness, fatigue, slow growth, brittle nails, etc
Probably the last one. It's the least realistic way to make your body healthy. If you are going to do exercise and make yourself healthy, friends would be helpful in that process and exercising is definitely a good way to be healthy.
There is many reasons why people have depression. Loss of a family member, bullying, physically abused or mentally abused. Persistent Depressive Disorder is Depression that lasts about 2 years or more it could cause change in appetite, sleep to much or too little, also a lack of energy or fatigue. You could also have low self-esteem even have trouble concentrating and making decisions. You could also feel hopeless you would need therapy and sometimes medications. There is about 9 different depression or more I hope this helps.