If you had your grandparents around when you were younger, you likely remember that trips to their home usually involved more cookies than vegetables, more staying up late with little to no exercise and perhaps even being exposed to more smoke. Most parents tend to think that their children are spoiled by their grandparents, but researchers now agree that it has a lasting negative effect on a child’s health.

More than 50 studies were recently conducted around the world to show the effects that grandparents had on a child’s health, and it turned out that grandparents had both a negative impact on weight and cancer risks. The children that were raised by grandparents as opposed to their parents, which happens to be about 25 percent of preschool aged children in the United States.

Many of the studies showed that weight was the most impacted by those that were living with their grandparents, as the children were much more likely to become obese. Some of the studies showed that there was little to no impact, while others suggested that there was an adverse effect. Of all of the studies, none yielded any results that said a child’s weight would be lower and in the normal range when being raised by grandparents.

Part of the reason for this is because grandparents have the tendency to spoil grandchildren. The research described grandparents as “indulgent” and “misinformed” about a proper diet for a child. Many of the foods contained high contents of fat and sugar that were part of an everyday diet, instead of just a treat that happens every now and then. Because of this, grandparents don’t seem to have an intention on harming health or promoting a poor lifestyle, and that it’s “unintentional.”

Some of the evidence also suggests that some grandparents grew up in hardship, and that being too thin was a sign that they weren’t living a better life. Added weight is seen as more of a status symbol in some of these homes where overfeeding was present. Among the factors was an increase of eating out instead of making meals at home, adding a lot of larger portions and unnecessary calories.

Research lead author Dr. Stephanie Chambers said that part of the reason grandparents have a worse effect on health is not only a lack of information from a time where there wasn’t as much, it’s also current targeting of information. “Currently, grandparents are not the focus of public health messaging targeted at parents and in light of the evidence from this study, perhaps this is something that needs to change given the prominent role grandparents play in the lives of children,” she said.

Chambers also added that “From the studies we looked at, it appears that parents often find it difficult to discuss the issues of passive smoking and over-treating grandchildren…While the results of this review are clear that behavior such as exposure to smoking and regularly treating children increases cancer risks as children grow into adulthood, it is also clear from the evidence that these risks are unintentional.”

“Given that many parents no rely on grandparents for care, the mixed messages about health that children might be getting is perhaps an important discussion that needs to be had.”

Linda Bauld of the Cancer Research UK group that co-funded of the study, saying that “This study reinforces the importance of the broader family picture. With both smoking and obesity being the two biggest preventable causes of cancer in the UK, it’s important for the whole family to work together.”

“Children should never be exposed to secondhand smoke, but it’s also important for children to maintain a healthy weight into adulthood, and in today’s busy world it’s often the wider family who have a role to play in keeping youngsters healthy. If healthy habits begin early in life, it’s much easier to continue them as an adult.”

Tam Fry of the National Obesity Forum says that expanding the message to grandparents is a good idea, but it might not be so easy. “Finding a doting grandparent who is confident enough to follow rules laid down by (the child’s mother) and to the letter is frequently a rarity,” she said.

“Both (grandparents) can leave themselves wide open to manipulative and increasingly savvy grandchildren in their desire to please the little darlings,” she added. “They bring out (treats) at the slightest hint of a tantrum…(And) the thought of losing children when out in the park may result in the kids being under house arrest – sweets on demand and woefully short on exercise.”