The Effects of GLP-1 Receptor Agonists on Chemosensory Function and Ingestive Behavior

Taste detection thresholds will be assessed for sweet, salty, sour, and bitter stimuli (sucrose, sodium chloride, citric acid, and urea, respectively) using a two-alternative forced-choice staircase procedure, in which participants identify which of two samples contains the taste stimulus. Separate outcomes will be reported for each taste quality: sweet, salty, sour, and bitter. For each taste quality, the threshold will be calculated as the geometric mean concentration at which the stimulus is reliably detected and will be reported in mmol/L. Lower threshold values indicate greater taste sensitivity.

Suprathreshold taste intensity will be assessed for sweet, salty, sour, and bitter stimuli (sucrose, sodium chloride, citric acid, and urea, respectively) using the general Labeled Magnitude Scale. Separate outcomes will be reported for each taste quality and stimulus concentration. For each taste quality, participants will rate the perceived intensity of suprathreshold stimulus concentrations. The scale ranges from 0 to 100, with 0 anchored by "no sensation" and 100 anchored by "strongest imaginable sensation of any kind." Higher scores indicate greater perceived taste intensity.

Taste hedonics will be assessed using a food modification task in which participants create preferred concentrations for sweet, salty, sour, bitter, and fatty stimuli. Separate outcomes will be reported for each stimulus type: sweet, salty, sour, bitter, and fatty. For each stimulus type, the outcome will be the preferred concentration selected by the participant. Higher values indicate preference for a higher concentration of that stimulus and do not necessarily indicate a better or worse outcome.

Fat taste perception will be assessed using edible strips containing different concentrations of linoleic acid. Participants will rate the perceived intensity of each strip using the general Labeled Magnitude Scale. Separate outcomes will be reported for each linoleic acid concentration. The scale ranges from 0 to 100, with 0 anchored by "no sensation" and 100 anchored by "strongest imaginable sensation of any kind." Higher scores indicate greater perceived fat taste intensity.

Olfactory function will be assessed using the ArOMa-T test. Participants will smell odor stimuli and provide computer-based responses to questions assessing olfactory performance. The outcome will be the ArOMa-T test score, with higher scores indicating better olfactory performance.

Olfactory function will be assessed using the SCENTinel test. Participants will smell odor stimuli and provide computer-based responses to questions assessing odor detection, odor identification, odor intensity, and odor pleasantness. Separate outcomes will be reported for each SCENTinel component. Higher scores indicate better odor detection or identification performance, greater perceived odor intensity, or greater perceived odor pleasantness, depending on the component assessed.

Food preferences will be assessed using the Leeds Food Preference Questionnaire. Participants will view food images and rate how much they like and want to eat each food item. Ratings will be used to assess explicit liking and wanting for foods.

Attentional bias to food cues will be assessed using a Food Stroop Task. Participants will view food-related and non-food words and respond to the color of each word while ignoring the meaning of the word. Response patterns will be used to assess attentional bias toward food-related cues.

Questionnaire-based measures will be used to assess food cravings, food cue responsivity, food-related intrusive thoughts, perceived food reward, and eating behavior. Participants will complete the Food Cue Responsivity Scale, the Modified Trait and State Food Cravings Questionnaires, the Power of Food Scale, the Food Noise Questionnaire, and the Reasons Individuals Stop Eating Questionnaire. These questionnaires will assess sensitivity to food-related cues, typical and momentary food cravings, food-related intrusive thoughts, perceived responsiveness to the food environment, and reasons for stopping eating, including motivations and physical cues related to meal termination and satisfaction.

Dietary intake will be assessed using ASA24, the Automated Self-Administered 24-Hour Dietary Assessment Tool. Participants will complete three 24-hour dietary recalls on different days, including two weekdays and one weekend day, to report foods and beverages consumed over the previous 24 hours.

Cephalic-phase salivary response will be assessed by measuring saliva production at baseline and during exposure to a food cue. Saliva will be collected during a baseline period and again while participants simulate eating a food item by focusing on its smell, taste, and texture. Saliva will be collected in graduated tubes and weighed to quantify salivary output. Change in salivation from baseline to food cue exposure will be compared across groups.