Hunger Games: How our gut manages appetite and metabolism

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It goes without saying that our gut has a pivotal role in converting food into energy but you might be surprised to know that the trillions of microbes that live in our gut and their genetic material (aka the gut microbiome) might have a further and rather significant influence on our metabolism. In fact we now know that our gut bugs have a crucial role in this process and help to regulate a multitude of biochemical processes that impact on appetite, blood sugar levels and our weight.

Shaping and nourishing the gut microbiome can therefore help us to support our metabolic health.

Here’s how…

Feed Me Now

Hunger is precipitated by a chain of events much of which comes from the gut. Let’s start with the feeling that we need to eat. This is driven by hormones such as neuropeptide Y and ghrelin. Then there are hormones that help to suppress appetite which includes peptide YY, cholecystokinin and glucagon-like peptide-1 (GLP-1). All of these hormones act on the hypothalamus, an area of the brain that oversees our daily intake of food and our eating behaviour. The hypothalamus constantly assesses our requirements and regulates our metabolism using the extensive input it receives from hormones like those mentioned above.

Ghrelin is the ‘feed me now’ hormone: it is fast-acting and signals the body to eat. When your stomach is empty, cells located in its lining secrete ghrelin, which is sent to the hypothalamus to signal that its time to eat. This is when specialised cells in the gut release GLP-1 to slow down food leaving the stomach which helps to manages appetite and our insulin response. At the end of the meal when we are satisfied our gut releases appetite suppressing hormones such as leptin and peptide YY. This switches off the need to eat so that we know when enough is enough.

At least this is how it should work. However, there can be reasons why there might be glitches in our appetite system. One of these that has been suggested is ‘leptin resistance’ which means the body doesn’t respond properly to the hormone’s signals. Another reason that has been suggested is chronic inflammation which can disrupt this communication and as such interfere with an appropriate response to leptin so that the brain doesn’t receive cues that we have had enough to eat. It has been suggested that this inflammatory feedback loop may lead to overeating and as such weight gain.

Furthermore our gut microbiome, specifically some of the metabolites our gut microbes produce, like short-chain fatty acids (more on these next), can directly influence the secretion of GLP-1 which can then improve or impair glucose metabolism depending on the composition of our gut microbiome.

Chain Reaction

One of the main group of positive substances that our gut microbes produce are called short chain fatty acids or SCFA’s. These SCFA’s are created via the fermentation of dietary fibre by our gut microbes. However, even though SCFA’s are produced in our gut, they have a very important role in the entire body that have a significant impact on how we manage inflammation as well as balancing blood sugar levels, metabolism and weight as previously mentioned. One SCFA, butyrate, has been positively associated with having a protective role against obesity and metabolic diseases.

Therefore we need an enriched and balanced microbiome in order to have a plentiful supply of these SCFA’s.

Good Bugs Versus Bad Bugs

Research shows us that the composition of microbes has a significant role on our metabolic health since our gut microbiome influences insulin sensitivity and weight. In fact, studies show that distinct differences and functioning of the gut microbiome with conditions such as obesity and type 2 diabetes. Moreover, other studies suggest that depending on the make up of an individual’s gut microbiome it can predict that person’s response to certain weight loss interventions. Broadly speaking having more of the good bugs means we have a more favourable response overall.

The Inflammatory ‘Alarm Bell’

Chronic inflammation can be a key driver of metabolic conditions which can also be linked to the health of the gut, specifically the gut health barrier. Where the gut barrier can become compromised or ‘leaky’ this can allow unwarranted substances to pass into our system. Among these substances are pro-inflammatory molecules derived from bacterial toxins called lipopolysaccaharides (LPS). When these LPS escape the confines of the gut and enter our system they can trigger a cascade of inflammatory responses. This inflammatory ‘alarm bell’ can be referred to as metabolic endotoxeamia and has been associated with various metabolic conditions. Nourishing the health of the gut barrier is therefore a central part of supporting metabolic health.

So how can we support our metabolic health via our gut?

1. Fuel with fibre – aiming for 30+ plants per week as this helps to create a more diverse gut microbiome and provide myriad sources of fibre and polyphenols that feed our gut microbes to produce SCFA’s. Moreover fibre helps us to better regulate our glucose and insulin response.

2. Allow fasting time – as this allows the gut adequate time to manage anti-inflammatory processes and for the juxtaposing hormone to insulin, glucagon, to perform its role adequately. Aiming for a 12-hour overnight fast is doable for most of us and trying to allow around 4 hours between meal times would be ideal.

3. Enrich the gut microbiome – with fermented foods such as live natural yogurt, hard cheeses, sauerkraut, kimchi and miso which are rich in ‘probiotics’ organisms which can have a positive impact on our gut.

4. Support the gut barrier – with eating fermented grains such as sourdough over processed white refined grains. Taking a daily dosage of ION* can also enrich the health of the gut barrier and promote improved cell to cell communication in the gut which is a key component of metabolic health.

5. Chew chew chew – slowing down and taking time over our meals is one of the best way to regulate our appetite and allow hormones like leptin to kick in. Moreover prioritising meal times can also act as crucial pockets of recovery throughout our day to de-stress which leads nicely onto the final point.

6. Stress less – with chronic stress comes chronically raised levels of the hormone cortisol that suppresses the growth of good bugs in the gut and can create direct damage to the gut barrier which can drive inflammation. Chronic levels of high cortisol can also act as a fat storage hormone, typically around the middle area, so if you want to have a slimmer waistline adding in some meditation or other daily mindfulness practise is a really important part of this.

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