Mothers lead the way for their children. And new research finds that the paths that moms walk (or the couches they sit and smoke on) make a powerful difference in their children’s propensity to become obese.

A study that tracked close to 17,000 female nurses and their 24,289 kids has found that women who practiced five healthy habits – maintaining a healthy weight, exercising regularly, eating a nutritious diet, consuming no more than moderate quantities of alcohol and not smoking cigarettes – had adolescents that were 75 percent less likely to be very overweight than the children of moms who practiced none of those healthy habits.

When kids followed their moms along that optimally healthy path, they were 82 percent less likely to be obese in adolescence than were the children who followed their mothers down a path including none of the healthy behaviors, the study found.

The new research was published this week in the journal BMJ.

Parents’ genetic contributions to their offspring do influence a child’s propensity to obesity. But the steep run-up in child obesity seen in the span of fewer than two generations can’t possibly be explained by genes alone. Today, nearly 1 in 5 children between the ages of 6 and 19 is considered obese, a rate that’s more than tripled since the 1970s.

Since nature can’t be blamed, the authors of the new research went looking for the influence of nurture in driving child obesity. (And let’s face it: When you think of nurture – or blame, for that matter – moms are No. 1.)

The new study parses out which healthy habits seem to contribute most to protecting teens from obesity.

Mom’s own weight status appeared to exert an outsize influence on her kids’ risk for obesity. The children of women whose body mass index falls in the “healthy weight” range were 56 percent less likely to be obese than were the offspring of either underweight or obese moms.

The children of mothers who don’t smoke were 31 percent less likely to be obese than were the children of moms who did smoke.

When mothers got 150 minutes or more of moderate-to-vigorous exercise a week, their kids were 21 percent less likely to be obese in adolescence than were the children of less active moms.

So few of the women who participated in the study were considered heavy drinkers that the authors could not compute the influence of high alcohol consumption on the obesity risks of their offspring. But they did find a small benefit to the children of women who were light or moderate drinkers over teetotalers. When mom consumed between one and seven servings per week, her kids’ risk of obesity was between 11 percent and 20 percent lower, respectively.

However, the children of women whose diets scored in the top 40 percent of the federal government’s healthy-eating guidelines were not less likely to be obese than were the children of women whose nutrition choices landed them in the remaining 60 percent. Given mothers’ seemingly key role in preparing meals and modeling good nutrition habits, this finding was a bit of a surprise.

That mom’s dietary choices were not as influential as her other health-related choices may reflect a reality of modern-day childhood, the authors explained: Children’s diets are influenced by many factors, including school lunches and the food options they encounter in their neighborhoods.

The new findings lend support to the idea that programs to reduce obesity in children need to look beyond the children themselves.