Being harsh on your kids makes them fat

According to researchers, attempts by one parent to counterbalance the harsh behaviour are not always effective in lessening that risk.

"Harshness leads to problems with physical health and no matter how hard a spouse tries, they may not be able to erase those effects," said lead study author Thomas Schofield from Iowa State University in the US.

"Instead of saying, 'I'm the law and my wife is the gospel' or something like that, better to acknowledge that in terms of harshness, your spouse is not going to be a buffer for the child, so behave responsibly," Schofield added in the paper, published in Social Science and Medicine.

Researchers videotaped the interactions of 451 two-parent families to assess parenting behaviour and look at changes in the child's health several years later from adolescence to young adulthood.

However, when they measured the effect on body mass index, the health risk of harsh parenting increased as warmth from the other parent increased.

No parent in this sample was observed hitting their adolescent, but Schofield said there were other signs of physical aggression, such as pinching and pushing.

The results indicated that the differences in physical health and BMI were not evident at the beginning of adolescence. The effects persisted into young adulthood after many had moved out of their parents' homes

This exposure can have a lasting effect on the developing brain during childhood and early adolescence, he added.

"The best thing we can do is encourage parents to not be harsh. If we want to make sure we're protecting children's health and positive physical health into young adulthood, the best and safest conclusion is to avoid being harsh," Schofield advised.