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TORONTO - In 2002, a New York Times magazine article suggested that the medical establishment may be unwittingly making us overweight by recommending a reduced-fat diet, and a craze for low-carb eating began.
In What If It's All Been A Big Fat Lie? well-known science reporter Gary Taubes argued that researchers, nutritionists and public health officials had pushed low-fat diets without adequate supporting evidence.
Taubes wondered if maybe Dr Robert Atkins, the long-controversial creator of the eponymous diet, had it right after all - maybe fat and calories didn't really matter, and carbohydrates did.
Five years later, Taubes' new book Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease argues that the kind of calories we consume matter more than the quantity.
Good calories come from foods without sugars or easily digested carbs - meat, fish, cheese, non-starchy vegetables.
Bad calories come from foods that overstimulate insulin secretion - bread, potatoes, pasta, sugar, tropical fruits.
In the book, Taubes comes to a few controversial conclusions: heart disease is caused by carbohydrates, not dietary fat; carbs are the most likely dietary causes behind diseases like Alzheimer's and cancer; exercise makes us hungry, not thin; and the fewer carbohydrates we eat, the leaner we'll be.
Good Calories, Bad Calories examines an alternative hypothesis to the calorie- and fat-centric idea through decades of literature and clinical data on diet and obesity, Taubes says.
It's another way to explain observations about diet and weight gain, he says, one for which strong data existed.
"If we had taken this other fork in the road," he asks, "what would we have come to believe?"
When we digest carbohydrates, they are metabolised and absorbed into the bloodstream as glucose or sugar. When blood sugar levels rise, our brain tells our pancreas to produce insulin.
One of the hormone's roles is to lower our blood sugar levels, but another is to regulate fat metabolism.
Insulin tells our cells to take in circulating lipids and convert them to triglycerides, storing energy in our fat tissue. "Insulin literally makes you fat," Taubes says.
Taubes believes that working off those carbs on a treadmill might not help either.
Instead of making us lean, he says, exercise makes us hungry, putting our bodies in a position of always trying to reach a balance.
The real cause of obesity may not be too much food and not enough exercise, he says, but instead could be an underlying physiological mechanism at work.
The overeating and sedentary behavior associated with overweight people may be a result of their weight, not the cause of it.
Conversely, lean people may not be that way because they're physically active; they may be physically active because their fat cells make more energy from the food available to them.
"When you have this hypothesis, you don't have to blame obesity on behavior anymore," Taubes says.
"You don't have to assume that if somebody's fat, they are defective, and you're not because you're lean. They have a defect, but it's in the way they metabolise carbohydrates."
Carbs may not just make us fat, Taubes writes, they might also kill us.
Diseases like heart disease, cancer and Alzheimer's tend to cluster, and being overweight ups your risk of eventually getting one of them, so he argues that it's possible that excess weight could be the cause.
Taubes has already weathered a storm of criticism for his earlier writing on diet and obesity.
The Center for Science in the Public Interest, a non-profit health and science advocacy group, accused Taubes of ignoring evidence contrary to his hypothesis and featured researchers who felt they'd been misrepresented in the Times magazine article.
Two days after the release of Good Calories, Bad Calories, the Corn Refiners Association, a group representing American corn syrup manufacturers, issued a statement refuting Taubes' assertion that sugar and high fructose corn syrup are especially unhealthy.
For now, the jury on diet and weight is still out.
In an article in the October issue of the Journal of the American Dietetic Association, Glenn Gaesser, author of It's the Calories, Not the Carbs, writes that his analysis of peer-reviewed research showed that even so-called "bad" carbohydrates aren't that unhealthy.
On the other hand, obesity expert Dr David Ludwig - interviewed by Taubes for the Times article - found that mice developed a condition called "fatty liver" when fed a diet high in starchy carbs.
Both the American Heart Association and the American Diabetes Association recommend avoiding added sugars and eating whole instead of refined grains, but they also advise avoiding cholesterol and saturated fat.
Taubes knows that some people think he is a quack, but argues that if beliefs aren't held up to scientific examination, we'd still be in the Dark Ages.
"Science doesn't work without extreme skepticism and without challenges to the conventional wisdom."
Good Calories, Bad Calories is not a diet book, Taubes emphasises.
"It's a plea to take this hypothesis seriously, because it has the advantage of explaining the observations, which the current dogma cannot do."
The book is meant to appeal not only to patients but to doctors, researchers and public health officials, Taubes says.
To that end, 150 copies have been sent out to various professionals in the field of nutrition and obesity.
He is curious about the response, he says, and hopes that at least some of them will read it.
"I thought if one in 10 of them does, then that 10 per cent is likely to start a debate that is likely to spread from there."
- REUTERS
