The principal research question is whether the ingestion of stevia (rebaudioside A) in encapsulated format will have any effects on blood glucose, appetite and food intake in healthy human volunteers.

Obesity presents a major global health crisis; developing healthier diets is a key goal. Excess consumption of caloric sweeteners contributes to the alarming high rates of overweight and obesity. Non-nutritive sweeteners, like stevia, are used to decrease energy content of foods and beverages. Very recently a systematic review and meta-analysis conducted and published by WHO, concluded that non-nutritive sweeteners use results in small reduction in body weight and BMI in adults, as assessed in RCTs.

In a previous set of studies from our group we showed that a single-dose of a stevia-sweetened beverage prior to lunch leads a lower energy intake compared to consuming water or a sugar-sweetened beverage (Stamataki et al J Nutr. 2020; 150(5):1126-1134. doi: 10.1093/jn/nxaa038). This effect was confirmed to be present in the long-term, as in another 12-weeks trial we demonstrated that individuals in the stevia group (they started consuming stevia drops twice daily with habitual drinks before their meals) demonstrated a significant spontaneous reduction in energy intake compared to the control group (Stamataki et al Nutrients. 2020;12(10):3049. doi: 10.3390/nu12103049).

In a nutshell, this research so far has showed that stevia consumption elicits benefits in appetite and energy intake, without affecting physiological responses such as postprandial glucose response. Taking this research a step further, it is crucial now to answer whether sweetness without calories was the key component of these outcomes, in other words would stevia have the same effects if it was not tasted, if sweet taste (in the oral cavity) was bypassed?

As such the main aim of this study is to evaluate the effects of stevia in a capsule vs placebo on appetite and energy intake and elucidate whether stevia elicits similar effects when sweet taste is bypassed.

Inclusion Criteria:

• Age 18 - 40 years
• BMI between 18.5-24.9 kg/m2
• DEBQ for restraint eating ≤ 3
• Healthy - general good health
• Currently not taking any medication (other than females taking the oral contraceptives, or medication that does not affect taste, and glucose response)
• Regular breakfast eaters (≥5 times per week)
• Stable weight, ≤ 5 kg last 3 months
• No self-reported food allergy or intolerance to foods supplied during the study
• The participant is capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the consent form.
• The participant is able to read, comprehend and record information written in English.
• A signed and dated written informed consent is obtained from the participant.

Exclusion Criteria:

• Age under 18 years or over 40 years old.
• BMI ≥25 kg/m2 and <18.5kg/m2
• Subjects who are currently on a diet
• Subjects who follow special diets for weight maintenance, such as Atkins Diet, Weight Watchers, gluten-free diet, The Zone diet, Raw Food Diet etc.
• Vegetarians, vegans
• Subjects having breakfast fewer than 5 times per week.
• Presence of any chronic condition requiring medication that might affect our results (e.g. diabetes, mental diseases, gastrointestinal diseases)
• Subjects with eating disorders (binge eating disorder, bulimia etc)
• Subjects who are currently experiencing anxiety or depression.
• Participants who drink more than the NHS guidelines (14 units per week)
• Participants who are, or may be, pregnant, or currently lactating.
• Subjects who regularly consume dietary supplements for weight loss, muscle building etc.
• Subjects who have aversions to foods related with the study.
• Subjects with food allergies or intolerance related with the foods/ drinks of the study.
• Habitual NNS consumers, >1 can of diet beverage or >1 sachet of low calorie sweeteners (corresponding to 1 spoonful) per week.
• The participant cannot read, comprehend and record information written in English.