Being overweight is bad for your kid, this not only affect their health now, but also affect their health in the future.
I heard that this may make a kid easy to get fat and lose weight harder when he/she grow up. I can’t remember where I heard this, here is the main point:
When a grown-up become fat, his/her fat cells become large, but the amount of his/her fat cells does not change.
What about an overweight kid? When a kid become fat, not only his/her fat cells become larger, but also his/her fat cell number increases. Because he/she is still growing.
(When a person lose weight, the fat cell can shrink back. But the amount of fat cell will not decrease. )
When the kid grow up, he/she is easy to become fat and it is more difficult for him/her to lose weight since he/she has more fat cells than those who have normal weight when they are a kid.
I don’t know if it is true, if you are interested in it, you can do some more research or consult a fitness professional.