Cigarette Smoke Linked to Childhood Obesity

A new study shows that when it comes to kids' weight, secondhand smoke in a child's early years as a toddler is almost as bad as smoking while pregnant.

Cigarette Smoke Linked to Childhood Obesity Tomasz Wrzesien/Shutterstock

It's no surprise that smoking around children isn't a good idea, but findings recently published in the journal Nicotine and Tobacco Research link secondhand smoke to a new risk: childhood obesity. The study found that 10-year-olds who had been frequently exposed to smoking in their home as toddlers had waists that were up to three-fifths of an inch wider and BMI (body mass index) scores between .48 and .81 points higher than children who were not exposed to smoke. Although those numbers might not seem like a lot, the effect on kids' health is significant.

Related: How to Safely Quit Smoking While Pregnant

Why secondhand smoke is linked to higher body fat in kids

Similar studies on secondhand smoke have been done before, but they didn't account for other factors that may contribute to childhood obesity. This is the first study to isolate smoking as the link to kids' higher weight. "We found a consistent, dose-dependent negative influence of household smoke exposure between ages 1.5 and 7 on waist circumference at age 10," lead study author Linda Pagani, Ph.D., a professor at the University of Montreal's School of Psycho-Education, tells The results went "above and beyond the competing influence of other important child, family, and gestational confounders [variables]." In fact, Pagani found that secondhand smoke is an even bigger risk factor for obesity in kids than having a mother who is overweight. "The association was almost twice as large as the influence of maternal BMI on children's waist circumference," she says.

The reason for the link between childhood obesity and secondhand smoke isn't known, but Pagani has some theories. "Young children have ventilation needs per kilogram of body weight that are approximately two to three times higher than adults due to their immature vital systems, resulting in more noxious effects of household smoke exposure compared to adults," she says. According to her, this leads to endocrine imbalances, negative effects on the cardiovascular system and altered neurological development, all of which can impact weight gain.

Similar effects on children's weight as smoking while pregnant

The most surprising finding of the study is that the risk of childhood obesity from secondhand smoke is almost as great as that from smoking during pregnancy. Although smoking while pregnant carries additional dangers to the baby, like miscarriage, placenta problems, birth defects, low birth weight and greater rates of SIDS, avoiding smoking after baby is born is important to your child's health, too. "A surplus of body fat prior to adolescence is likely to represent greater health risk outcomes than weight that is gained during other periods of development," says Pagani, noting it could lead to cardiometabolic issues like heart disease, diabetes and stroke later in life.

Pagani says to avoid smoking inside your home as well as in the car. But what about going outside for a cigarette? Pagani says there are no actual studies showing the negative effects of the type of "third-hand smoke" (the lingering fumes after a cigarette is put out) that stays on clothes and hair, but that doesn't mean it's not a problem. "There are serious dangers of third-hand smoke," she says. "If parents move into a new home where there were smokers, ditch the existing carpets, wash the drapes and verticals, and get those walls washed. That environmental third-hand smoke is highly toxic."

According to the CDC, children whose parents smoke around them get sick more often, have less developed lungs and are more prone to asthma, ear infections, bronchitis and pneumonia. This new link to childhood obesity is just one more reason to stop smoking. To get help quitting, visit