Experimental Study to Investigate the Effect of a High Fibre, Polydextrose-enriched Tomato Soup on Food Intake, the Experience of Appetite and Biomarkers of Satiation and Satiety

The science underpinning both short (episodic) and long (tonic) term appetite regulation demonstrates that foods higher in macronutrients such as fibre can, under certain experimental conditions, produce great decreases in feelings of hunger and increases in fullness, post consumption, compared to equi-caloric loads of high carbohydrate or high fat. Given that fibre increases the release of GLP-1, slows down gastric emptying, prolongs nutrient absorption and, over long-term use increases the generation of short chain fatty acids (SCFAs) which have been linked to improved satiety responding, it is plausible that it will produce strong effects on within meal processes of satiation and satiety over the short- and long-term. Fibre has also been suggested to influence carbohydrate fermentation (via generation of these SCFAs) and improve the insulin response, additionally improving satiety. Ingredients may be added to boost fibre content such as the use of polydextrose, which is a non-digestible polysaccharide usually used as a dietary fibre in foods. Polydextrose has also been shown to increase levels of SCFAs due to its slow fermentation and has been related to reductions in subsequent intake and/or reduced hunger.

The aim of the current study is to assess the impact of a high fibre, polydextrose enriched tomato soup (experimental) or a low fibre tomato soup (control) on food intake, the experience of appetite and biomarkers of satiation and satiety.

Sample size: 86 males aged between 18 and 55 years with a body mass index (BMI) of between 23.0 and 28.0 kg/m2. A subset of 28 participants will undergo additional finger prick blood glucose and hydrogen breath test measures to assess biomarkers of satiation and satiety. Power calculations to ensure sufficient participants are included were based on power expected for a medium effect (0.25) at 80% power for a 2 condition between-measures design using G*power.

Methods: Participants will be invited to three full test day (baseline control, session 1; first dosing, session 2; one day prior to final dosing, session 3) sessions in which they will be provided with breakfast (tailored to individual resting metabolic rate (RMR) using the Schofield equation), the preload condition (receiving a high fibre polydextrose enriched or control tomato soup) one hour before an ad-libitum lunch and followed four hours later by an ad-libitum dinner and snack box. All test days will involve the use of standard operating proceedures. Pre-packaged portions of soup will be provided for a 4-week dosing period between study sessions 2 and 3 for all participants.

A subset of participants (N=28) will additionally undergo 3 further testing sessions (baseline control, session 0; second dosing, session 3; final dosing, session 4) in which a breakfast will be provided followed by the test product with additional glucose and carbohydrate fermentation measures collected for 3 hours before a light fixed portion meal.