Imagine going into a cheese shop to buy some decadent Blu di Bufala, but your purchase is denied by public ordinance because your body fat level is deemed too high. And then, when you're at the corner store to buy candy, you are denied because the attendant's health app buzzes, indicating your blood-sugar levels were already peaking.

Those may seem like illogical extremes, but they illustrate how uncomfortable some people are about the role of public health initiatives. Instead of programs designed to fight obesity, cut cancer rates and prevent premature deaths, these people see the potential infringement of their personal freedoms.

Remember the scorn when San Francisco taxed the toys in Happy Meals to dissuade parents from making unhealthy meal choices for their kids? Or the outrage when then-New York City Mayor Michael Bloomberg attempted to ban supersized sugary soft drinks (a move that other municipalities are considering)? And how about the derision Toronto's Mayor Rob Ford dumped on the city's chief medical officer of health when he called for a reduction in speed limits on residential streets – citing the direct relationship between increase in speed and pedestrian injuries and deaths?

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No one doubts the importance of public health officials when they are leading the fight against Ebola in Africa or SARS closer to home. Historically, they have succeeded in pushing for vaccinations, seat-belt use and improved standards for drinking water, food and sanitation.

But in their attempts to educate and influence public behaviour (and maintain sustainable health-care budgets), municipal and provincial health officers have been known to elicit the ire of politicians, industries and the public, especially regarding issues on which there is no exact science defining the health threat. On the use of e-cigarettes, for example, or the impact of fracking by energy producers on water quality.

The e-cigarette debate is particularly complicated. The battery-operated devices – which mimic the look and feel of conventional cigarettes without the tobacco, producing vapour instead of smoke – are hailed by some as the key to quitting smoking.

But others, including the World Health Organization, have called for stricter regulation because of the child-friendly flavours and the addictive nicotine that many, but not all, contain. Since 2009, Health Canada has basically left the file alone. Because e-cigarettes with nicotine have not been approved for sale in this country, the selling and advertising of the devices is actually illegal. But that hasn't stopped vendors and consumers.

Health officials are left to enforce a patchwork of rules. Nova Scotia plans to regulate e-cigarettes like tobacco; Quebec is considering the same, as is Vancouver. Red Deer, Alta., has passed legislation banning the use of e-cigarettes in public places, and Montreal passed a councillor's recommendation calling on the province to treat e-cigarettes like other tobacco products. Toronto banned e-cigarettes in city workplaces, and chief medical officer David McKeown has asked both the Ontario and federal governments to restrict advertising, limit access by youth, and implement a ban on smoking e-cigarettes even on public patios.

In an effort to make sense of the regulations, the e-cigarette issue is on the agenda for provincial and territorial health ministers, who are meeting in Banff, Alta., on Monday and Tuesday.

What authority do medical officers have to protect public health? Only British Columbia and Ontario have laws protecting the independence of medical officers of health. Earlier this year, the New Brunswick Medical Society called on the province to enshrine such independence after its chief medical officer of health, Eilish Cleary, was criticized by politicians for raising questions about the health impacts of fracking by oil and gas producers.

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Advocates say it's critical to protect public health officers from political interference because it's their job to side with the greater good – as opposed to personal or economic preference. Consider Toronto Mayor Rob Ford's response to McKeown's attempt to address speed limits: Along with calling McKeown an "embarrassment," Ford characterized the idea as "nuts, nuts, nuts" and the proposal was shelved.

And as it is, provincial and federal governments are not obliged to implement their health experts' policy suggestions.

Dr. Perry Kendall, provincial health officer for B.C., said reception of public health suggestions varies depending on the governments of the day, their philosophies and what resources they have available. "It also depends on how the recommendations are presented, or how the recommendations are made," he said. "Governments don't tend to like to be surprised or critiqued too vehemently … Advocating for policies is best done with a good evidence base to explain why a policy change or shift would be valuable, what it might do for the people."

Dr. James Talbot, Alberta's chief medical officer of health, said it's important for local and provincial officers to address public health issues at the appropriate level. "A provincial medical officer of health would be unlikely to know the local conditions well enough to speak with authority about what was happening in that region," Talbot said.

Other issues are more appropriately dealt with starting at the provincial level, he said, such as making sure the ministry is prepared should an Ebola case present itself.

New Brunswick's Cleary said the biggest challenge is in changing public perception on what kinds of health concerns warrant attention, especially when risks are less visible.

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"People understand having the medical officer of health in something immediate, like a pandemic, because we're accustomed to that," she said, "but the threats to health nowadays are more insidious."

Issues such as diets, urban design and air quality, said Cleary, are all hugely important influencers of public health, but it's a different type of risk than managing a communicable disease or forest fire.

"Medical officers of health have always run up against industry, for example, or trade, because if it's seen that it may cost more to do something or erode into profits then there has been resistance," she said. "It's harder, sometimes, to demonstrate poor health outcomes as clearly [to the public] because they are things that happen in the longer term, like obesity … We know what the problems are, but it's hard to persuade people about the things that are needed to fix them."

With a file from Carly Weeks