The researchers, from the University of Alabama at Birmingham, conducted a meta-analysis of human studies that examined the effect of nutritively sweetened beverages (NSBs) on body mass index (BMI).
They found 12 relevant studies, half of which showed that subjects gained weight when sugary drinks were added to their diets, and half of which attempted to reduce sugary drinks. The latter studies consistently showed no effect on BMI, the researchers found.
They wrote: “The current evidence does not demonstrate conclusively that NSB consumption has uniquely contributed to obesity or that reducing NSB consumption will reduce BMI levels in general.”
Three of the study’s four authors noted conflicts of interest in their review, including “grants, honoraria, donations and consulting fees from numerous food, beverage, pharmaceutical companies, and other commercial and non-profit entities with interests in obesity.”
Policymakers under pressure
Despite writing that it is difficult to discern the effects of NSB consumption on obesity, the researchers said that policymakers are now under pressure to take action to deal with obesity in the United States.
“Policymakers need to act on the pressing problem of overweight and obesity, which regrettably means that decisions must now be made on imperfect knowledge,” they wrote.
One idea that policymakers have repeatedly raised is that of taxing sugary soft drinks as a way to tackle obesity, and debate about whether such a strategy would work is ongoing. In some states, lawmakers have dropped this aspect of the argument, and suggested instead that soda taxes could be used to address budget deficits.
Nevertheless, the researchers behind this latest review said that observational studies have been shown to have little merit, and recommended that randomized controlled trials with overweight individuals should be conducted “for whom there is suggestive evidence of effect.”
Source: Obesity Reviews
doi: 10.1111/j.1467-789X.2010.00755.x
“Nutritively sweetened beverage consumption and body weight: a systematic review and meta-analysis of randomized experiments”
Authors: R. D. Mattes, J. M. Shikany, K. A. Kaiser and D. B. Allison