Healthy diets for a healthy weight: exploring physiological mechanisms related to dietary fibre and non-nutritive sweeteners

Challenges

A key challenge for researchers and policymakers is to produce and implement evidence-based guidelines for the UK food system to reduce obesity trends. 65% of the Scottish adult population is classified as overweight and 28% as obese. In general, the Scottish diet is poor quality being too high in calories, processed foods, fats, sugar, and salt; it is equally too low in fibre, oily fish, and vegetables. Poor diets are a major contributory factor driving food and health inequalities. Dietary inequalities are notably socially patterned according to socio-economic status, where overweight and obesity prevalence is higher in socially disadvantaged groups.

Dietary fibre is found inherently in food is a key metabolic activity is to promote fermentation by the microbiota that primarily inhabits the lower gut. This results in a rise in short-chain fatty acids thought to confer several health benefits, including the suppression of food intake. Although increased fibre intake can be helpful, it is still a relatively underexploited dietary approach to tackle obesity. Therefore, foods that promote satiety and reduce energy intake may be promising tools in weight management.

Food additives, such as artificial sweeteners, could influence responses to dietary fibre. There is emerging evidence that these compounds can have antimicrobial properties that could disturb the normal ecology of the gut microbial ecosystem. Replacing sugar with non-nutritive sweeteners may inhibit the growth of bacteria for a healthy gut microbiome and may even promote harmful bacteria and metabolites. For humans to benefit from dietary fibre, fermentation is essential. This will not happen effectively if additives kill off the beneficial bacteria needed for this process. Furthermore, sweeteners may prevent weight loss if microbiota disruption adversely affects satiety signalling from the gut. Indeed, reports suggest that some artificial sweeteners are associated with weight gain and obesity as well as disrupted glucose control, thereby being potentially as harmful as the sugary drinks they replace.

In Scotland, there is a ‘fibre gap’, with the population consuming well below the recommended levels for good health. It is crucial to explore the reasons for inherently low fibre intake in Scotland by considering the attitudes of Scottish consumers to dietary fibre and its link to health using a focus group approach. This is important as consumer-based evidence suggests the need for a move away from a meat-based diet towards increased fibre intake for health reasons, as well as to transition towards a sustainable, environmentally friendly food supply, appears to be being missed or ignored by consumers in Scotland.

Questions

Solutions

This project aims to understand the physiological role of dietary fibre in the regulation of appetite and its role in achieving a healthy weight and the potential interference of food additivities (non-nutritive sweeteners) on this physiological response.

Attitudes of Scottish consumers to dietary fibre and non-nutritive sweeteners 

We explore public attitudes towards artificial sweeteners and dietary fibre. To do this, we are conducting focus group research to draw upon respondents' attitudes, feelings, beliefs, experiences and reactions. This group is purposely selected individuals to reflect consumers within areas of food inequalities and living with obesity. We are working with participants to highlight relevant and potentially modifiable interventions and leverage points likely to effect changes. The results are being disseminated to obesity and poverty alleviation advocacy groups, patient representatives, and food system and public health policy stakeholders.

Exploring the efficacy and physiological responses to a high-fibre (pectin) diet

We also implement controlled diet trials with healthy but overweight/obese individuals to investigate the key dietary components of physiological mechanisms associated with appetite control for a healthy weight, mediated by gut hormone release. This approach addresses the impact of dietary fibre on people living with obesity and food inequalities. The outcome of this study is highlighting the importance of habitual fibre intake as a potential modulator for gut microbiome activity and composition.

Effects of a non-nutritive sweetener with a high-fibre diet on metabolic health and composition of gut microbiota

We are conducting a controlled dietary intervention study to assess the impact of non-nutritive sweetener (sucralose) on a high-fibre diet, on gut microbiota activity and composition and makers of metabolic health. We are also exploring how the inclusion of high-fibre and non-nutritive sweeteners leads to glycaemic control.

Overall, this project is providing policymakers with important insights related to increasing fibre consumption across the population - a key public health target. Additionally, fibre is a naturally high component of fruits and vegetables, which must be increased at the expense of meat to address the issue of sustainable diets. Lastly, sugar replacers are being widely used by the food industry to overcome the sugar levy, so it is important to ensure there are no unintended consequences.