Confirmed by the first systematic review of available evidence commissioned by the World Health Organization, increasing or decreasing intake of sugar is associated with changes in body weight.
Increased consumption of so-called free sugars, including additives to foods and those naturally present in honey, syrups and fruit juices, led to an average gain of 1.8 pounds (0.8 kilograms) in body weight in adults, researchers at the University of Otago in New Zealand found in a review of 71 studies. Limiting the analysis to studies lasting longer than eight weeks, weight gain was 2.7 kilograms, they said.
The study adds to a debate over public policy aimed at curbing the obesity epidemic and related diseases, including New York City’s decision to restrict sales of large-sized sugary soft drinks. The WHO commissioned the review in preparation for updating its 2003 recommendation that free sugar be limited to less than 10 percent of energy intake.
The authors said in a published paper that, "When considering the rapid weight gain that occurs after an increased intake of sugars, it seems reasonable to conclude that advice relating to sugars intake is a relevant component of a strategy to reduce the high risk of overweight and obesity in most countries."
The authors stated that, cutting consumption of sugars led to an average 0.8 kilogram reduction in weight in adults, according to five studies that ranged from 10 weeks to eight months. Among studies in children, comparison of varying levels of consumption suggested a "significantly increased risk" of being overweight associated with higher intakes, they said.
Chizuru Nishida, a coordinator in the WHO’s Department of Nutrition for Health and Development in Geneva, said in an interview, "This review clearly indicates the positive association, which is quite striking, given that no such systematic reviews have been conducted so far." The study defends the current WHO guidelines that have been criticized as having no scientific basis, she said.
The WHO has commissioned a second study, to be published sometime in the next few months, looking at sugars and tooth decay and will consider both analyses in its updated recommendation, Nishida said.
"Reducing the amount of sugar consumed in drinks deserves special attention because of the strength of the evidence and the ease with which excessive sugar is consumed in this form," said Walter Willett, a professor at the Harvard School of Public Health, and David Ludwig, a professor at the Boston Children’s Hospital, in an editorial accompanying the study. "But questions remain. What is a desirable limit?"
The WHO’s report stated that, "Efforts to reduce sugar intake are appropriate, but they should form part of a broader effort to improve the quality of carbohydrates," they said. "Action should be taken at many levels, including education programs, improvements in food and drinks provided in schools and work sites, and supplemental nutrition programs for people with low incomes."
WHO’s Department of Nutrition for Health and Development in Geneva: Jan 2013