Your modeling is your best teaching tool. How do you eat? How much do you exercise? How do you deal with your feelings? The best way to help your child is to take care of you.
Often kids are eating to numb out the pain they are experiencing at home, or they take on the pain of their parents or guardians. The best thing parents can do for their kids is to take care of themselves and their relationships. Parents cannot give from an empty vessel. It is crucial that you find ways to nurture yourself. If you are emotionally unhealthy, your child will feel it. If you are in an unhealthy relationship with someone, your child will feel it. If you are ready to pop because your own emotions are not dealt with, your child will feel it.
If you are not eating in healthy ways, your child will see it. If you are not exercising, your child will most likely follow your lead. Instead of feeling guilty about any of these things, use them as permission to take care of you. If you don't do it for you, do it for your child.