Abstract Background Several health organizations recommend lowering the consumption of sweet-tasting foods. The rationale behind this recommendation is that a lower exposure to sweet foods may reduce preferences for sweet tasting foods, thus lowering sugar and energy intake, and in turn aiding in obesity prevention. However, empirical data supporting this narrative are lacking. In fact, relatively little is known about the contribution of long-term sweet taste exposure on one’s sweetness preferences. Methods The primary objective of this randomized controlled trial is to assess the effect of low, regular and high dietary sweetness exposure on preference for sweet foods and beverages, and to compare these effects between intervention groups. One hundred and eighty adults aged 18–65 years with a BMI of 18.5–30.0 kg/m2 will be recruited and randomly allocated to either: low dietary sweetness exposure (LSE) (10–15% daily energy from sweet tasting foods), regular dietary sweetness exposure (RSE) (25–30% daily energy from sweet tasting foods), or high dietary sweetness exposure (HSE) (40–45% daily energy from sweet tasting foods), for 6 months, followed by a 4-month follow up. Intervention foods are provided ad libitum, covering approximately 50% of the daily number of food items, to include sugar-sweetened, low-calorie-sweetener-sweetened and non-sweet foods. The primary outcome measure is the difference in change in sweetness preference from baseline to 6 months between intervention groups. Secondary outcomes include: change in sweet taste preferences at different time-points; taste intensity perception; behavioral outcomes: food choice and intake, sweet-liker type, food cravings, dietary taste preferences and dietary taste patterns; anthropometric outcomes: body composition, waist-hip circumference, body weight; and biochemical outcomes: glucose variability and biomarkers related to CVD and diabetes. Discussion This study will generate important data on the effect of dietary sweetness exposure on sweetness preferences in terms of effect size and change, duration of change and its impact on food intake, body weight status and associated health outcomes. Trial Registration The study protocol has been registered on ClinicalTrials.gov (ID no. NCT04497974, Registered 4 August 2020, https://clinicaltrials.gov/ct2/show/NCT04497974 ) and approved by Wageningen’s Medical Ethical Committee (ABR no. NL72134).

Sweet taste preference and liking have been assessed with various methods, yet there is no consensus in the literature on which method is most sensitive across a range of foods. The current studies explored several methods to assess sweet taste preference, liking and perceived intensity across various familiar and unfamiliar foods in Dutch consumers. In experiment 1, five different sweet foods, each with five sweetness concentration levels were evaluated on preference, liking and perceived intensity, using two methods for measuring liking and preference: ranking (n = 10), rating (n = 10); one for measuring perceived intensity: rating (n = 10); and one combining preference, liking and perceived intensity: structured napping (n = 10). The ranking method, despite having the highest discriminative power, gave no indication of inter-sample spacing nor absolute scores. In subsequent studies, ranking was thus combined with rating as "Ranking on a scale" (RoS). Experiments 2 (N = 31), 3 (N = 28) and 4 (N = 28) tested the RoS method across various familiar and unfamiliar foods and/or food forms. In Experiments 2 and 4, inverted-U-shaped hedonic responses were observed for all foods, and differences in preference for different sweetness concentration levels were detected. Experiments 3 and 4 showed that familiar foods were more liked than unfamiliar ones across all sweetness levels (Experiment 3 (F(1,1322) = 14.8, p <.001); Experiment 4 (F(1,803) = 38.1, p <.001)). Hence, RoS seems to be a viable method for assessing sweet taste preferences in both familiar and unfamiliar foods, among consumers. In future work we will apply this method to better understand the role of sweet taste exposure on preferences for a range of sweet foods.

A crucial challenge in investigating motivated human eating behaviour is to go beyond subjective measures, by developing reliable methods capable of objectively quantifying the dynamic aspects of appetitive motivation. We developed and tested a novel effort-based task (Grab-to-Eat Task (GET)), utilising handgrip force as a motivational measure, to capture eating motivation dynamics throughout consumption. Sixty normal-weight young adults were allocated to one of two hunger state conditions (hungry or satiated) and performed a continuous reinforcement-based task, during which sips of chocolate milk were self-administered with a handgrip force transducer. Motivation was covertly assessed by the magnitude of effort exertion towards each sip. Cumulatively, hungry subjects exerted more effort and consequently consumed more chocolate milk than satiated ones. Effort exertion declined throughout consumption in both groups, with the rate of decline being two-fold greater in hungry subjects. Furthermore, effort exerted in the initial stages of consumption predicted subsequent intake. Present results fit in the theoretical framework of reward-related motivation and suggest that the developed paradigm is sensitive to eating motivation dynamics throughout consumption and to differences in eating motivation related to hunger state. Further validation, ideally involving functional neuroimaging, would be imperative. In the future, this paradigm could be used to investigate eating motivation dynamics in various populations, conditions and food products.