Sweet Consumption and Subsequent Sweet Food Preferences and Intakes

Participants will be randomized to receive instructions to either increase, decrease or make no change to sweet food consumption for 6 days, and impacts on food preferences and intakes will be assessed at baseline and after 1 week. Preferences for sweet and non-sweet foods will be assessed during a taste test at each assessment time, where six different foods will be rated. Sweet and non-sweet food consumption will also be measured at a subsequent breakfast at the assessment time. Buffet meals composed of sweet and non-sweet foods suitable for consumption at breakfast will be provided ad-libitum.

A subset of participants (selected at random) (10 participants randomized to increase sweet food consumption and 10 participants randomized to decrease sweet food consumption) will also be assessed via MRI and fMRI scanning to investigate brain structure and functional connectivity.

• Dietary Instructions (Behavioral): Dietary Instructions

Primary outcomes

• Sweet Food Preferences [Week 1]: Preferences for various sweet foods/fluids, assessed using a taste test, where participants sample several sweet and non-sweet foods and rate them for pleasantness on a 100mm Visual Analogue Scale, from 0 to 100mm. Higher scores signify stronger preferences
• Sweet Food Choices [Week 1]: Selection of sweet foods/fluids at a given meal, assessed where participants can consume freely from a meal composed of sweet and non-sweet foods, and proportion of sweet foods consumed is measured as a percentage of weight consumed

Secondary outcomes

• Hunger and Thirst [Week 1]: Ratings of subjective perceptions, assessed using 100mm VAS from 0 (lower hunger) to 100 (higher hunger) mm
• Sweet Food Perceptions [Week 1]: Perceptions for various sweet foods/fluids, assessed using a taste test, where participants sample several sweet and non-sweet foods and rate them for intensity on a 100mm Visual Analogue Scale from 0 to 100mm. Higher scores signify stronger perceptions
• MRI Static Brain Scan (Subset of Participants Only) [Baseline to week 1]: Static brain scan gained from a 3-Tesla Siemens Magnetom Lumina scanner (Siemens Healthcare, Erlangen, Germany), used to investigate brain structure, where the anatomical structure (e.g. size, shape) of the brain, measured via surface area (mm squared), will be compared at baseline and week 1
• fMRI Composite Functional Brain Scan (Subset of Participants Only) [Baseline to week 1]: Composite fMRI functional scan to investigate brain functionality and connectivity in response to a 10 min cognitive task, will be gained from a 3-Tesla Siemens Magnetom Lumina scanner (Siemens Healthcare, Erlangen, Germany), where patterns of activity will be measured using blood oxygenation level-dependent (BOLD) contrast whole-brain functional images, acquired using a T2-weighted gradient-echo Echo Planar Imaging (EPI) sequence and a 32-channel head coil during a 10 min cognitive task, and will be compared at baseline and week 1 (for full details of this methodology see Yankouskaya A, et al., Biology, 2023, 12, 211.)

Sex: All, ages: 18 Years to 65 Years, accepts healthy volunteers

Inclusion Criteria:

1. aged 18-65 years;
2. habitually consume breakfast;
3. able to provide consent and complete all study materials;
4. able to attend Bournemouth University for testing.

Exclusion criteria:

1. individuals who are pregnant or breastfeeding;
2. underweight (BMI <18.5);
3. have pre-existing clinical conditions such as diabetes mellitus, eating disorders, Crohn's disease and other illness's leading to participants receiving external nutritional advice and dietary restrictions;
4. have pre-existing medical conditions affecting swallow ability, taste and smell perception;
5. currently or within 3 months of starting the study are following a specific dietary programme (e.g.: Slimming World);
6. current smokers or have smoked within 3 months of the study start date.

Participant flow

Outcome results

• Sweet Food Preferences (Primary), Mean, score on a scale: Dietary Instructions: Increase Sweet Food Consumption 66 +/- 3; Dietary Instructions: Decrease Sweet Food Consumption 63 +/- 3; Dietary Instructions: Usual Diet 68 +/- 3
• Sweet Food Choices (Primary), Mean, percentage of weight consumed: Dietary Instructions: Increase Sweet Food Consumption 36 +/- 4; Dietary Instructions: Decrease Sweet Food Consumption 25 +/- 4; Dietary Instructions: Usual Diet 27 +/- 4
• Hunger and Thirst (Secondary), Mean, score on a scale: Dietary Instructions: Increase Sweet Food Consumption 57 +/- 18; Dietary Instructions: Decrease Sweet Food Consumption 65 +/- 20; Dietary Instructions: Usual Diet 64 +/- 18
• Sweet Food Perceptions (Secondary), Mean, score on a scale: Dietary Instructions: Increase Sweet Food Consumption 71 +/- 3; Dietary Instructions: Decrease Sweet Food Consumption 77 +/- 3; Dietary Instructions: Usual Diet 73 +/- 3
• MRI Static Brain Scan (Subset of Participants Only) (Secondary)
• fMRI Composite Functional Brain Scan (Subset of Participants Only) (Secondary)

Adverse events

Time frame: 1 week

• This project is associated with Clinical Trails Registration: NCT03427658

• Study Protocol and Informed Consent Form (PDF, 2025-05-31)
• Statistical Analysis Plan (PDF, 2024-04-26)

• Katherine M Appleton, Principal investigator, Bournemouth University