Project Lead
Challenges
Overconsumption is manifestly a human problem, whether at the level of individual food intake, which is the primary cause of obesity, or the usage of the world’s natural resources - a driver behind the global climate and biodiversity crises. The way we produce and consume food is one of the major changes that need to be made to mitigate these challenges. There is a general recognition that a reduction in the level of our meat consumption in favour of more plant-based diets would be beneficial.
There is a potential win-win here for both the planet and our health. Plant-based foods are often high in dietary fibre. There is a strong recognition that there need to be higher levels of fibre intake than currently consumed at a population level. However, another important facet of high-fibre diets is that they can act as a natural brake on our food intake, limiting the amount of food we consume and, therefore, weight gain.
There is strong evidence that dietary fibre can suppress food intake and body weight gain in animals. In humans, high fibre intake and microbe diversity correlate with lower long-term weight gain. However, these effects are not always seen and thus a key question is, what determines when the fibre is effective in restraining food intake and body weight gain? To address this question, we need to better understand the importance of different types of fibre and how these fibres act in the gut. There are several theories to explain how fibre restrains food intake, including changes to key bacteria in the gut microbiome, increased levels of short-chain fatty acids (SCFAs) and increased release of the gut hormones that suppress appetite. However, how changes in the gut microbiome are translated into changes in SCFAs to influence gut hormone signalling is still a matter of debate.
Questions
- How can we develop our understanding of the physiological effects of interventions on dietary health?
Solutions
The purpose of this project is to examine how two different dietary fibres, pectin and oligofructose inhibit high-fat food intake at the level of the gut and how these responses compare to a mixed 4-fibre diet, more typical of normal human consumption.
We examine how the gut microbiome and the gut epithelium respond to these different dietary fibre formulations (pectin, oligofructose and mixed fibre). We show how any changes in microbiota translate into SCFA profiles and determine the host response to the three different dietary fibre diets at the level of gene expression in the gut epithelial cell layer.
A key aspect of this study is the use of three different fibre diets together with the analysis of the effects on the gut microbiome, SCFA generation and epithelial cell response all in the same study. We hypothesise that each fibre diet will stimulate quite distinct microbiota profiles, and this will generate correspondingly distinct patterns of SCFAs, yet at the level of the gut epithelia there may be a convergent response in terms of gene expression.
Overall, this project aims to show that the food intake and weight-restraining effects of fibre can be linked to some specific molecular events in the gut. More importantly, it is showing whether such events are only evident with a single fibre, such as pectin, or can also be observed with mixed fibre diets, which would be more representative of a normal human diet.
Project Partners
Progress
We have completed a mouse study where mice were provided meals with different dietary fibres alone or mixed, at different inclusion rates, on a high fat background. Results were as expected only for the individual fibres, with weight loss, mainly as fat, observed at the higher fibre levels. With the mixed 4-fibre diet, in contrast to the individual fibre diets, mice did not lose weight at any fibre level. These were novel findings indicating that the inclusion level of fibres in a mixed fibre diet may be important for body weight responses and may need to reach a threshold level to drive weight loss. Hormone analyses show the levels of two satiety hormones (PYY and GLP-1) may drive the body weight responses of the individual fibres (pectin and oligofructose), but no satiety hormone change correlated with the lack of body weight change with the 4-mixed fibre diet.
With regards to a comparison of the effects of different fibres (pectin, oligofructose and mixed fibre), on the profile of the gut microbiome; the results show differences as expected in levels of bacteria that can utilise the different fibre substrates. Closer examination of the responses using bioinformatic approaches, however, did not identify novel bacteria associated with the differential changes observed in body weight and fatness of the mice.
Against our original hypothesis, we report novel findings in that mice gut epithelial cell gene expression changes were observed in mice fed the individual fibres that differed from those fed the mixed fibre diets. Identification of the differential biological pathways involved may be important for enhanced understanding of fibre-related body weight responses observed.
This research provides insight into which types of fibre should be introduced into the diet to help healthy weight management. This could be particularly helpful for food reformulation.
This project was completed on the 31st of March 2023. The end of project report can be found here.
Blogs and case studies
Low consumer fibre intake may be due to confusion over which foods contain fibre
The health benefits of dietary fibre
Presentations, reports, and other outputs
A poster on “Specific Dietary Fibres Reduce Weight and Adiposity” was presented at the ENRA Science, Evidence and Policy Conference, 18th May 2023, Dynamic Earth, Edinburgh.
A poster on “Weight loss effects of mixed dietary fibres may be unachievable at recommended daily intake levels” was presented at the NuGo Conference, Impact of nutrition during different life stages – tracing the impact of diet on human health, Senigallia, Italy on 6-8 September 2023.
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The current crisis in public health (obesity, diabetes, cardiovascular disease, stroke and some cancers) is strongly rooted in an imbalance in dietary components. A healthy balanced diet not only requires reductions in fat, salt, sugar, and in overall calorie intake, but also an increase in fibre and an appropriate level of protein intake. The aim of this RD is to strengthen our understanding...
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