Reality check: Does your BMI increase each time you eat fast food?

If you’re in the middle of eating lunch, you should probably stop reading this story. Scott Barbour / Getty Images

TORONTO – Would an increase in your BMI every time you had a burger or fried chicken scare you away from fast food? A new study suggests that each time you eat the salty, fatty, easy-to-reach-for food, your body mass index creeps up by 0.03.

Even after taking exercise, age and income into account, American and Irish researchers say that every fast food transaction, however innocent a cheeseburger meal may look, is taking a toll on our waistlines.

The scientists are calling on governments to help consumers scale back on the amount of fast food they’re eating.

“The take-home message is that, although free-market policies are not to be demonized, it appears quite clear that in order to fight the obesity epidemic, a stronger role of government intervention is necessary,” lead author Dr. Roberto De Vogli, of the University of California, told NBC News.

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De Vogli and his team looked at the number of fast-food transactions and health records that documented BMI in high-income countries.

READ MORE: What Canadians want to know about what’s in fast food meals

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As fast-food purchases climbed, body mass index did too, and across all 25 countries. Fast-food transactions per capita increased from 26.61 to 32.76 and BMI increased from 25.8 to 26.4 over the span of 10 years.

Body mass index has become a key indicator around the world for obesity. A person with a BMI of 25 to 29 is considered overweight, but anything above 30 is considered obese.

Canadians had the sharpest increases in fast food intake, followed by Australia, Ireland, New Zealand, Norway and the United States. In countries with strict market regulation, lower increases were recorded – Italy, the Netherlands, Greece, Belgium, Portugal and Spain.

READ MORE: What’s in a chicken nugget? American scientist suggests only 50 per cent meat

Maybe it’s the fat, sugar and salt in excess that’s doing the damage. But other issues are involved: in higher-income countries, consumers eat out more, they lead busy lives that rely on convenient food and they tend to drive more, De Vogli said.

He plans to study in detail what is done with food and how processing changes caloric and nutritional intake.

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Canadian doctor and obesity expert Dr. Ali Zentner says that she isn’t surprised by De Vogli’s study:

“Unfortunately, this is in keeping with what is happening around the globe – in both developed and developing countries. We have seen a global rise in BMI across the last two decades,” she told Global News.

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“There is no single culprit at fault here but fast food, food insecurity and massive distribution of cheap, high-in-calorie, low-in-nutrition foods definitely play a role. You package this in an inexpensive and convenient package and present it to a vulnerable population and you have a recipe for disaster,” she said.

But BMI isn’t the only way to assess obesity risk, Zentner notes. When she takes on patients, she considers a string of factors beyond weight: co-morbidities, sleep apnea, fitness and obesity-related illnesses like diabetes, hypertension and heart disease.

READ MORE: What one woman in Gabon taught doctors about global obesity

“Make no mistake, (BMI measures) are not without flaws and obesity itself is more complex than just a number,” Zentner said.

De Vogli’s full findings were reported in the Bulletin of the World Health Organization.

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