Calories, not just fructose, make people fatter

Sweetener fingered as culprit in obesity epidemic among many wider causes, research shows

TORONTO — Fructose may not be one of the culprits in the obesity epidemic that it’s been made out to be, Canadian researchers are reporting.

After reviewing more than 40 published studies, researchers from St. Michael’s Hospital in Toronto found that fructose — a sweetener liberally added to soft drinks and processed foods — had no effect on weight compared with diets that provided the same calories from other carbohydrates.

People gained weight when they added extras calories in the form of pure fructose to their usual diet. But the gain may be entirely due to the extra calories, and not the fructose.

“Fructose may not be to blame for obesity,” said lead author Dr. John Sievenpiper, a research fellow at St. Michael’s and resident physician at Mcmaster University in Hamilton. “It may just be calories from any food source. Overconsumption is the issue.”

In a paper published this month in the journal Nature, U. S. researchers argued a growing body of scientific evidence shows fructose “can trigger processes that lead to liver toxicity and a host of other chronic diseases.” The authors said sugar is so toxic it should be controlled like alcohol; they even floated the notion of setting an age limit of 17 to buy pop.

Naturally found in fruit, vegetables and honey, fructose is a simple sugar that together with glucose forms sucrose, the basis of table sugar. It’s also in sweet and affordable high- fructose corn syrup, the most common sweetener in commercially prepared foods. It’s found in items ranging from soft drinks and chocolate bars to crackers and ketchup. Average daily fructose consumption has increased by more than 25 per cent over the past 30 years.

Studies have linked the obesity epidemic with the introduction of high- fructose corn syrup in the early 1970s.

Sievenpiper said the analysis is seductive, but highly flawed. “You could plot almost anything on the same graph — computer face time, driving cars, the suburbanization of the population, more sedentary behaviours — and probably find an equal parallel, or even a better fit with the overweight and obesity epidemic.”

Studies in lab animals have shown a diet in which fructose accounts for 60 per cent of total energy can lead to obesity, insulin resistance, elevated blood fats and high blood pressure.

However, “whether fructose in Western diets induces the same phenotype in humans is unclear,” Sievenpiper and his co- authors write in the journal, Annals of Internal Medicine.

For their study, the researchers looked at controlled feeding trials. They identified two types: “isocaloric” trials, where the diets are otherwise calorie matched — the only difference being one group ate pure fructose that was either baked into foods or sprinkled on cereals or beverages, while the other ate non- fructose carbohydrates in the same way — and “hypercaloric” trials, where one group consumed their usual diet and the other supplemented their usual diet with excess calories from pure fructose that was added to beverages.

In all, they reviewed 41 trials involving 756 participants. They found fructose had no effect on weight compared with diets that provide the same number of calories using nonfructose carbohydrates.

When fructose was added to a “usual” diet, there was a consistent and strong weight increase, Sievenpiper said. But “fructose, per se, is not the issue, it’s calories,” Sievenpiper said.