The rate of childhood obesity has doubled since the 1970s. Right now, nearly one third of Canadian kids are overweight or obese. This week, the Canadian Task Force on Preventive Health Care has issued new guidelines for health care providers on how to manage obesity. They are published in the Canadian Medical Association Journal, and you can read them here. I doubt they'll make a difference, given the fact that rates of obesity have continued to rise despite a lot attention in the media and among the people who look after your health. What caught my eye is an editorial that accompanies the guidelines because it's aimed not at health care providers but at schools and parents.

The editorial says schools should make exercise the norm by ensuring that mandatory physical education classes in elementary and high school. But it's not enough to have physical education. It says physical education classes need to be long enough and vigorous enough to meet recommended activity levels and not just token nods to exercise. It adds that schools need to cut sitting time by getting kids moving in class with short exercise breaks and what's called kinetic learning.

There's nothing controversial in any of that. What will get some parents upset are calls to encourage kids to walk or bike to school and calls to extend walk limits for school bus pick-ups and drop-offs. You've got to wonder whether parents would go for having their kids walk or bike to work on their own. Think of the media stories about kids who get abducted on the way home from school. It's no wonder parents are frightened of letting their kids wander on their own. And it's not just parents but society itself that has become risk averse.

You may remember the case of two kids picked up by police while walking home alone from a playground in Maryland in December 2014. The parents were investigated and eventually found responsible for what was labelled "unsubstantiated" child neglect. The decision means child welfare authorities will keep a file on the family for at least five years and leaves open the question of what would happen if the children get reported again for walking without adult supervision. All it takes is one child to disappear while walking to or from school to make everyone skittish about the benefit of exercise.

The next recommendation contained in the editorial is almost as controversial as getting parents to let their kids walk or bike to school. The editorial says high school kids are chronically sleep deprived. It proposes that high school start later in the morning to allow teenagers to get enough sleep. Last August, the American Academy of Pediatrics recommended that middle and high schools delay the start of class to 8:30 a.m. or later to align school schedules to the biological sleep rhythms of adolescents, whose sleep-wake cycles begin to shift up to two hours later at the start of puberty.

A National Sleep Foundation in the U.S. poll found 59 percent of 6th through 8th graders and 87 percent of high school students were getting less than the recommended 8.5 to 9.5 hours of sleep on school nights. It's a trend that has been adopted at high schools in several provinces including Ontario, B.C. and Saskatchewan.

This policy shift makes a lot of sense. A growing body of research suggests that there's a link between how much people sleep and how much they weigh. In general, children and adults who get too little sleep tend to weigh more than those who get enough sleep. Over the past 20 years, studies have documented that the amount of daily time spent sleeping has declined for infants, children, and adolescents. Cultural changes have likely contributed to this trend, including more 2-parent working families and longer work hours. A 2014 study in the journal Pediatrics asked the mothers of 1046 children about how long their child slept in a typical 24-hour period at 6 months, and then their daily sleep duration for each year between ages 1 year and 7 years. Compared with children who routinely slept the longest, kids who slept less were significantly more likely to be overweight or obese.

There's much at stake if we don't tackle the problem of childhood obesity - a powder keg for kids and for the health care system. Rising rates of childhood obesity mean an epidemic of early onset high blood pressure, type 2 diabetes and elevated cholesterol and triglycerides. In turn, that means higher rates of early onset heart disease, stroke, arthritis of the hip and knee and a rising need for joint replacement surgery at an early age. And, if that's not enough, we'll see rising rates of cancer. All of those things and more await us if we do nothing to stem the tide.