You set the example. Children do what they see.
If you eat junk food, so will they.
If you sit on your butt, so will they.
When ever an antibiotic, or steriod is given for what ever reason. After the round of medicine, give a probiotic. Include yogurt, cottage cheese, and fruits, and vegetables to replenish the good bacteria in the intestines. Dysbiosis is the main cause of obesity.
Fresh air, and sunshine. A good multi vitamin, to supply needed nutrients. Good fats, such as nuts, and seeds. Avoid frying, bake instead. Substitute good fats for bad, olive oil, coconut oil, and walnut oil, plain butter. Foods as close to the natural state as possible. Meaning, an apple not apple pie, nuts, instead of chips, whole grains, instead of pop tarts.