1.for me "to be healthy" means to eat healthy food, do exercises, be active, do sports etc.
2.It is important to keep fit, but in a right way. You must'nt eat nothing, it is dangerous, you must make a healthy lifestyle not just eating fruits and vegetables, you must do some sports, for example, football, basketball, ride a bicycle, tennis...
3.Do not eat fast food, eat more fruits and less sweets, more vegetables and less junk food. Be active, do exercises, do as much sports or activities as you can