Research into soda consumption and obesity is conflicted, review claims
Many studies have suggested a link between excessive consumption of nutritively-sweetened beverages (NSBs) and higher BMIs, but this latest research suggests that there may be a need for further randomized controlled trials (RCT) in overweight people in order to investigate whether the link between NSBs and obesity is causational. Randomized controlled trials are considered to be the most rigorous way to assess whether a cause and effect relationship exists between certain factors.
“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,” the authors wrote. “We recommend an adequately powered RCT with overweight persons, for whom there is suggestive evidence of an effect.”
They found that six studies showed a dose-dependent increase in weight with increased NSB consumption. However, meta-analysis of studies that attempted to reduce NSB consumption showed no overall effect on BMI, they said.
Three of the authors, including the lead author, Dr. David Allison, acknowledged conflicts of interest in the study, saying they had received “grants, honoraria, donations and consulting fees from numerous food, beverage, pharmaceutical companies, and other commercial and non-profit entities with interests in obesity.”
The researchers, from the University of Alabama at Birmingham (UAB), looked at data from 12 randomized controlled trials in human participants. They defined nutritively sweetened beverages as something one drinks to which a nutritive sweetener has been added, including regular sodas, fruit punches and chocolate milks, but not diet sodas, 100 percent fruit juices and unsweetened plain milk.
To be included in the review, studies had to last at least three weeks, body fat had to be measured at the beginning and end of the study period, and participants had to be randomly assigned to either drink or not drink nutritively sweetened beverages.
The authors concluded that although there is considerable support for a direct association from diverse literature, evidence from RCTs is lacking.
“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. “Understanding the risks associated with missteps, it is imperative future efforts be focused on the science most likely to fill current gaps in knowledge.”
Source: Obesity Reviews
(2011) Vol. 12, pp. 346–365 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