Sugar, non-caloric sweeteners and reward.

Rationale:

The prevalence of overweight and obesity is still increasing. The development of new and healthier food products, e.g. products in which sugar has been replaced by non-caloric sweeteners, may provide solutions to help people to meet dietary guidelines. However, besides taste, sugar also provides metabolic reward, which is important for consumer acceptance on the longer term. A reduced consumer acceptance on the longer term may reduce the effectiveness of non-calorically sweetened products for weight management.



Objective:

To determine the effect of replacing added sugar by non-caloric sweeteners in a nutrient-rich matrix (dairy drink yoghurt) and in a nutrient-empty matrix (soft drink) on reward value after repeated exposure.



Study design:

The study will use a randomized crossover design whereby subjects are repeatedly exposed to sugar sweetened and non-caloric sweetened versions of a yoghurt drink and a soft drink. The study consists of 2 periods with 3 parts: pre-measurements, a conditioning period, and post-measurements. In the conditioning period (5 days a week for 4 weeks), subjects will be offered a sugar sweetened or a non-caloric sweetened version of either a yoghurt drink or a soft drink 10 times in random order. Before and after this repeated exposure, reward value will be assessed with behavioural tasks and fMRI measurements. The behavioural tasks will assess the preference for the sugar sweetened and the non-caloric sweetened versions after repeated consumption. With the fMRI measurements, responses to the drinks in brain reward areas will be measured. In period 1, subjects receive either the sugar sweetened or the non-caloric sweetened versions of the yoghurts or the sugar sweetened and non-caloric sweetened versions of the soft drinks. In period 2, these conditions are switched.



Study population:

The study population consists of 40 (20 males/20 females) apparently healthy, normal weight, unrestrained, adults between the ages of 18 to 35. Only the males will participate in the fMRI part of the study.



Primary outcomes:

The primary outcome measures of this study are 1) the shift in product preference, i.e., the difference in preference for the sugar sweetened and non-caloric sweetened yoghurt drinks and the sugar sweetened and non-caloric sweetened soft drinks after repeated exposure (males and females) and 2) the change in brain reward responses to the sugar sweetened and non-caloric sweetened drinks after repeated exposure (males).

It is hypothesized that foods that have an intrinsic nutrient-rich matrix are less susceptible to changes in reward value due to replacing the sugar content than foods that have intrinsic a nutrient-empty matrix. Thus we expect that the reward value of the non-caloric sweetened yoghurt drink will not change over time and will remain similar to that of the sugar sweetened version. It is hypothesized that the non-caloric sweetened soft drink will decrease in reward value over time compared to its sugar-sweetened counterpart.

Every participant will visit the laboratory every day during the intervention periods.

In the conditioning period (5 days a week for 4 weeks), subjects will be offered a sugar sweetened or a non-caloric sweetened version of either a yoghurt drink or a soft drink 10 times in random order.