The Mouth - Gut - Brain Model

Obesity and associated conditions such as type 2 diabetes and cardiovascular disease are major global health concerns. A contributing factor is overconsumption of energy dense foods, rich in fat and sugar, driven by our hedonic and physiological desire to consume energy rich foods. One approach has been to reduce the energy content of foods whilst retaining the sensorial quality. The food industry has developed a wide range of healthier products. In order for these products to be successful, consumers must continue to purchase and consume them. However, recent studies have suggested that reducing the energy content of a food may have unintended consequences. Specifically, if a food looks, and tastes like it is rich in nutrients, the gut and brain systems prepare to expect a high energy intake. If this does not happen, as in the case of a reduced calorie food, the brain appears to induce hunger signals that drive the individual to overconsume at subsequent meals (rebound hunger), resulting in an increased calorie intake, thus negating the whole effect of consuming the reduced calorie food. This leads to consumer dissatisfaction with these products, and potentially to imbalances in appetite and hunger hormones that often cause rapid weight gain following periods of dieting.
Therefore we need to rethink how reduced calorie foods can be used more effectively to control energy intake. To do this, we need to understand the relationship between how we sense foods, how we digest and absorb the nutrients and how the brain responds to these processes and controls subsequent appetite signalling. This Mouth-Gut-Brain system is key to controlling our appetite and energy intake.

The aim of this project is to understand how the mismatch between sensory properties and nutrient intake of food controls our appetite and rebound hunger. The key question we aim to address is, by how much can the energy content of a food be reduced before rebound hunger and overconsumption occurs? The key impact will be our ability to modify reformulated foods to reduce the gap between sensory and nutrient signals in order for reduced-energy alternatives to satisfying and not result in subsequent over-consumption.
This project will focus on fat, as fat has the highest energy content, and the sensory properties of low fat foods are challenging for both consumers and the food industry. We will investigate the impact of reducing the fat content of foods by determining how the sensory properties control consumer expectations of satiety (feeling of "fullness"), and measure how much we can reduce fat content before consumers develop rebound hunger and overconsume at a subsequent meal.
Using this information we will design a more realistic food where the structure, physical behaviour and sensory properties are closely matched, but with a range of fat contents and fat type, to carefully control how much fat is "sensed" and how much is absorbed. We will measure how the appetite response of these foods controls the consumption of food in a following meal; and study differences between individuals who are sensitive or insensitive to fat content in foods. This will determine how much we can alter the sensory and fat content of food and still maintain an overall reduction in energy across subsequent meals.
Results will provide valuable information on how mouth-gut-brain signalling fundamentally controls appetite, and begin to unravel why different individuals may be more susceptible to rebound hunger following the consumption of reduced calorie foods. The research will also enable us to define a broader research programme to investigate mouth-gut-brain interface that will study in more detail variations between individual responses, and the biological mechanisms behind our behavioural measures (such as gut hormone levels).
Knowledge generated will enable better approaches to reduced calorie foods that are more effective at reducing energy intake in the longer term.

There is emerging evidence that reduced energy foods with a high sensory quality have limited effectiveness at reducing long term energy intake and weight management. This is thought to be due to the disparity between the sensory expectation of energy content / satiety and the actual physiological nutrient / energy uptake. This disparity in mouth-gut-brain signalling has been shown to result in rebound hunger and overcompensation of energy intake at subsequent meals. This study aims to combine sensory science, food structure and materials, consumer psychology and behaviour to determine the mechanisms that underpin this disparity and to determine the level by which the organoleptic properties and nutrient content can be altered to avoid rebound hunger and overcompensation of energy intake.
Initial experiments will measure the tolerance for fat reduction in a model food between sensory attributes and expected satiety; and determine the mouth-gut discordance by measuring subsequent appetite response. These results will inform the rational design of realistic foods, using the interfacial and colloidal properties of the emulsions and biopolymer microgels to closely match physical and sensory properties but with reduced fat content. The in vitro release and digestion of fat from the matrix will be used to finely control the difference between sensory expectation and actual nutrient delivery. Further human studies will determine the impact of controlled fat reduction on rebound hunger and overcompensation; both in individuals who are hypo- and hyper-sensitive to fat perception.
The outputs will inform the design of future projects to unravel the role of gut hormone signalling, as well as phenotypic /genotypic effects in consumer behaviour toward low energy foods. This will provide nutritionists, academics and the food industry with tools to develop effective dietary and weight management strategies to help combat of obesity, type 2 diabetes and cardiovascular disease.

We envisage the main long term vision for this work will be a programme of research projects aiming to improve the repeat consumption of healthier foods by rational design of foods with a defined relationship between the sensory perception, nutritional delivery, and psychological response that will minimize the consequences of sensory discordance in reduced energy foods. This priming project will have quantified the discordance between sensory signals and nutrient feedback in reduced fat food matrices, and designed snack food models that rebalance these signals leading to satisfying and satiating reduced fat foods. This model approach can then be rolled out to low sugar foods. However it will also enable subsequent projects to address the following research objectives:
Define inter-individual differences in the mouth-gut-brain relationship, and explore whether these are driven by phenotype or genotype.
Define the impact of reduced fat foods on GI hormone release and endocannabinoid response to further understand mechanisms underpinning the interrelationship between mouth, gut and brain. This will lead to predictive models through a systems biology approach.
Develop novel technological approaches to develop foods that can target and balance the delivery of sensory and nutrient signals.
Extend these approaches into developing real foods and determine the effect in whole meal scenarios. Long term dietary intervention and consumer behaviour studies will determine the long term impact on health in different population groups.
In addition to the academic research community, the outputs of this research will benefit a range of stakeholders. The research will address key questions that will help BBSRC deliver on its Food, Nutrition and Health research priority, as described above under academic beneficiaries. The food industry will be a key beneficiary through a fundamental understanding of how reduced energy foods impact on satiety, consumption and energy intake. This will lead to the development of food design strategies that will be more effective in achieving fat and sugar reduction goals. More effective food products will be more popular with consumers and therefore lead to improved satisfaction and repeat purchase. Consumers will ultimately benefit from this research through the development and availability of improved quality and more effective reduced energy foods. This strategy will not only benefit consumers who are actively seeking to control energy intake, but we envisage that these energy reduction strategies will become a standard approach in a wide range of standard, commonly consumed foods, that will an impart appropriate level of expected satiety, and thus should have a more widespread impact on energy intake. Following further work on different population groups, individuals who would benefit from these types of interventions will be more easily identified, and matched with appropriate solutions. The government and health care providers will benefit from this knowledge through the improvement of health and nutrition policies. These policies will not simply recommend reductions in dietary energy intake, but rather a tailored dietary advice that accounts for individual phenotype that will result in a more effective sustainable diet for improved weight control. As most cases of obesity are the result of lifelong moderate overconsumption, this research should ultimately help contribute to a reduction in incidence of obesity, by moderating dietary intake over the lifecourse. This will eventually lead to better control over the incidence of related metabolic diseases such as type 2 diabetes and cardiovascular disease.
The project provides excellent training opportunity for staff and students. It will expose them to a broad yet integrated multidisciplinary approach to solving an important diet and health issue; vital experience for future researchers working in this field.