A review of about forty published studies investigating the association between weight gain and fructose consumption reveals that these sugar molecules, found in fruits, vegetables and honey, may be getting a bad rap.
"Limit your daily calorie consumption - don't overeat!"
Lead author John Sievenpiper, M.D., Ph.D., from St. Michael's Hospital in Toronto, and his colleagues looked at two groups of studies to learn about how fructose might or might not cause weight gain.
They looked only at studies involving free crystalline fructose - not high-fructose corn syrup - and studies had to include feeding trials that lasted at least a week.
In 31 of the studies, two participant groups consumed the same number of daily calories. One group ate non-fructose carbohydrates, and the other ate pure fructose, baked into their food or sprinkled into their beverages or on cereal.
The results of those studies showed no weight gain among the fructose-eaters.
In 10 different studies that Dr. Sievenpiper's team reviewed, one group ate their normal diet while another group consumed fructose as extra calories beyond their typical diet or a control diet.
This time, the fructose-eaters put on extra pounds, but they were consuming additional calories compared to the group eating only their usual diet, so it could be just the extra calories that caused the weight gain, Dr. Sievenpiper said.
The researchers concluded that based on these studies, the evidence does not support the idea that fructose calories cause greater weight gain than any other calories.
"Fructose may not be to blame for obesity," Dr. Sievenpiper said. "It may just be calories from any food source. Overconsumption is the issue."
This review was limited by the quality of the studies the researchers looked at, most of which were poor quality and had methodological limitations.
Most of the studies were three months or shorter and involved fewer than 15 healthy participants usually of normal weight. The average age of participants ranged from 21 to 65.
The authors recommend the larger and longer studies of better quality to better assess the role of fructose in weight gain.
The research, funded by the Canadian Institutes of Health Research, appeared online February 21 in the Annals of Internal Medicine.
Several of the authors have received support from a wide range of companies and research bodies, including ones associated with Coca-Cola, Kellogg's, Quaker Oats, Dean Foods, the California Strawberry Commission and various nut boards and institutes.