Effect of a Liquid Tonic Drink on Post-meal Glucose and Insulin Responses

A randomised, double blinded, placebo-controlled crossover design clinical trial conducted at the Mary MacKillop Institute for Health Research (MMIHR, Australian Catholic University) for individuals with overweight/ obesity. This study will measure the postprandial glucose and hormone responses to a high-carbohydrate meal with/ without a liquid tonic drink.

Twenty individuals living with overweight/ obesity will be invited to attend the university laboratories on 2 separate occasions to participate in a postprandial (meal) challenge. Participants will consume the same high-carbohydrate meal on each visit, with or without a liquid tonic drink. This will be a cross-over design study, where participants will consume a placebo drink on the alternate visit. Participants will remain in the laboratory for 3-hours following the meal with a venous cannula in place, and have blood samples taken at regular timepoints. Blood samples will be analysed for glucose and appetite hormones. Participants will also wear a continuous glucose monitor throughout the period which encapsulates both study trials.

Inclusion Criteria: * Aged ≥30-64 years * Body Mass Index (BMI) of ≥27.0 kg/m2 Exclusion Criteria: * younger than 30 or 65 years or older, * a BMI less than 27.0 kg/m2, * have an allergy to any of the components in the plant-based tonic (see section 6), * pregnant or breastfeeding, * regularly skipping breakfast (i.e. not consuming breakfast on 5/7 days per week), * any diagnosed metabolic (e.g. diabetes), endocrine (e.g. hyperthyroidism), gastrointestinal (e.g. Crohn's) or cardiovascular (e.g. heart failure) abnormalities, * on an energy-restricted diet; significant weight fluctuation in the previous 3 months (\>5% body weight), * high alcohol consumption (\>14 units/week) (as per Alcohol Drink Guidelines), * medication that is used to treat blood glucose, * unable to attend in person testing sessions, or * unable or unwilling to provide blood samples.