Effects of sugar-sweetened drinks on psychological and metabolic outcomes.

Background. Various lines of evidence indicate that negative metabolic consequences follow when a person regularly drinks a large quantity of sugar-sweetened beverages (SSBs). What is not known is whether SSBs also produce negative psychological effects, such as impairments in short-term memory and increased impulsiveness. Switching from SSBs to ‘diet’ beverages (non-nutritive sweetened beverages; NSBs) would seem to offer a relatively easy dietary change. However, it has been claimed that this can be counter-productive in at least some circumstances. Aims. 1. To test whether SSB consumption produces impairment on psychological tests, relative to NSB consumption and a water control condition; 2. To test whether the effects of NSB consumption depends on other aspects of a person’s diet (e.g. consumption of sweet energy-rich foods). Design. In a non-blinded 3-group parallel design over a 12-week period the Sugar group is given SSBs, the Diet group is given NSBs and the Water group is given water. Metabolic and cognitive/behavioural measures are taken at the outset of the intervention (Initial test), after 6 weeks (Midway test), at the end of the intervention (Completion test) and approximately 12 weeks later (Follow up test). Main predictions: 1. In the Completion test the primary psychological outcome measure, scores on the Logical Memory test, will be lower in the Sugar group than in the other two groups. 2. In the Completion test the primary metabolic outcome, waist:hip ratio will be larger in the Sugar group than in the other two groups.