Sugar-sweetened and artificially-sweetened beverages in relation to obesity risk

Pereira,M.A., (2014) Adv.Nutr. 5:797-808 10.3945/an.114.007062

OBJECTIVE: To identify the important methodological nuances across studies of SSBs (Sugar Sweetened Beverages) and weight gain/obesity risk to bring more clarity to the state of the science and to address remaining research needs. A secondary aim was to critically review the literature on the possible association between artificially sweetened beverages (ASBs) and obesity risk.

DESIGN: Review based on a Medline search for original scientific research papers in English language published 1946-2012. Included studies were prospective cohort studies of >6 months duration or RCTs with body weight or body fat as the outcome and with quantitative estimates of the associations.

SETTING: Various.

PARTICIPANTS: Children, adolescents and adults.

MAIN OUTCOME MEASURES: Summary of mechanisms for an effect of beverages on body weight regulation, summary of prospective observational and experimental studies, and recommendations for further research.

RESULTS: Mechanisms: The primary hypothesised mechanism for the postulated effect of SSBs on weight gain is blunted satiety relative to solid foods. Experimental evidence for this is not conclusive but is accumulating. Other characteristics of SSBs that are consistent with possible body weight dysregulation include large portion sizes, and effects on postprandial glycaemia and insulinaemia through glycaemic index or glycaemic load. The purported mechanism through which ASBs may increase weight gain is through a dysregulation of appetite control due to the mismatch between intense taste of sweetness and lack of energy consumed, which may stimulate appetite and thus lead to weight gain. The evidence is however inconsistent for an effect of ASBs on appetite and weight gain.

Literature Appraisal: Prospective cohort studies SSBs: 12 studies were identified in children and adolescents. They provide weak evidence for a positive association of SSBs on weight gain/obesity risk. There is significant potential for confounding and other biases, and for dietary measurement error. 11 studies were identified in adults and were judged to be of high quality regarding size, duration and statistical analysis. They show greater consistency for a positive association than studies in youth, but the effect sizes are modest (typically =/>1 serving per day associated with 1 to 2 pounds difference in body weight over many months or years). Studies are also subject to confounding and measurement error. Prospective cohort studies ASBs: 5 studies in children and adolescents show no clear association with body weight gain/obesity risk, and those showing positive associations could be explained by reverse causality. Combined with 6 studies in adults, the overall results suggest an inverse association between ASBs and body weight gain/obesity risk, but the evidence is not consistent and biases cannot be ruled out. RCTs: Of 5 trials of SSBs and ASBs in children and adolescents none showed an overall effect on change in BMI between groups. Of 5 trials in adults, 4 observed an effect on energy intake but only 2 showed a significant effect of modestly higher weight gain in the SSB group, the other 3 showing no difference.

CONCLUSIONS: The totality of the scientific evidence to date shows a pattern across studies of increased risk of weight gain/obesity risk with higher intake of SSBs. It is difficult to establish the strength of the association and independence from other potentially confounding factors. There is somewhat consistent evidence from prospective cohort studies and RCTs that ASBs may be protective in preventing obesity vs SSBs. Future RCTs should address mechanisms of actions, and assess behaviours on both sides of the balance equation, efficacy and effectiveness, and ensure good measurement of background habitual diet, physical activity and other potential modifying factors.