Taking care of our gut will support our digestive health, as well as having an influence on our mental health and immune response. There is research to show that optimal gut health can also support weight loss. Much of this is due to our gut microbiome – containing trillions of bacterias, fungi and viruses. We start developing the gut microbiome even before we are born, and as we grow, the microbiome diversifies. The more diverse the gut microbiome, the better it is for our overall health. Certain foods can help to better our gut health, whilst others may destroy some of the gut microbiome and reduce diversity. The gut microorganisms have a role in the way foods are digested and absorbed, as well as influencing our hunger and satiety hormones, which will then have an impact in our weight management.
How to know if your gut is healthy?
There are signs and symptoms to look for which will indicate you have a healthy gut. For example, if you have a regular bowel movement pattern, this likely indicates healthy efficiency of your gut. There is no set frequency of how often you should pass stool, and guidance can be anywhere between 3 times a week to 3 times a day. The key is that it should be consistent and happening at the same time. Any changes in bowel habits from normal can indicate a sign of imbalance.
The gut transit time, which is the time taken from eating and digesting the food to travelling through the gut and being excreted, should be around 28 hours. Longer transit times can increase risk of constipation, and shorter transit times could mean that nutrients are not being absorbed as well as possible.
The type of stools passed is a good indicator of how healthy the gut is. The Bristol Stool Chart, published in 1977, is a stool scale used to class different forms of stool into 7 categories.
Ideally, stool should be type 4, where it has a smooth texture, is sausage shaped and sinks in the toilet bowl.
There should be no discomfort during the bowel movement, and you should not need to strain or push, to pass the stool.
How you feel day to day can also be a good sign of a healthy gut. The bacteria in the gut produce gas as a byproduct of digestion, and passing gas is healthy and normal. However, if someone is experiencing persistent bloating and gas, this can be a sign of some sort of gut imbalance.
Symptoms of an unhealthy gut
- Intolerances to certain foods:
If you experience side effects such as bloating, abdominal pain or nausea when eating certain foods, this can be a sign of an imbalance and intolerance in the gut. Lactose intolerance occurs due to the lack of lactase enzyme, which is responsible for digesting lactose sugar. It can be quite common, with lactose intolerance being present in up to 100% of American Indians and Asians! - Infrequent or too frequent bowel movements:
If you are struggling to pass bowel movements more than 3 times a week, or have the urgency to pass stool more than 3 times a day, this can be a sign of an under-active or overactive digestive system. Slow transit time can be a sign of low fibre intake from the diet, as well as disorder of the enteric nervous system. At the other end of the scale, passing stool more than 3 times a day can indicate that food is passing too quickly through the digestive system, which can increase risk of nutrient malabsorption.
- Infections:
Having an infection such as gastroenteritis, will lead to symptoms of an unhealthy gut. This includes vomiting, diarrhoea and abdominal pain. If you experience frequent pain and bowel changes, it is recommended to reach out to your GP or a gastroenterologist.
- Pain and discomfort when passing stool:
Frequent pain and other symptoms such as bloating or passing gas more than normal can be an indication that there is an imbalance in the gut, and the body may be struggling to digest foods. If you need to strain when going to the toilet, this is also a sign of an unhealthy gut, as passing stool should not cause pain. - The type of stool:
Looking at the Bristol Stool Chart above, an unhealthy gut can lead to stools that are types 1-2, as well as types 6-7. Stools should sink and not stick to the toilet bowl, and floating stools can be an indicator of too much fat, which the digestive system can struggle to digest, or higher amounts of gas. If stools are a different colour than usual and it doesn’t relate to what you have eaten, this can be a sign of imbalance.
If you experience any of the symptoms and signs of an unhealthy gut, we recommend reaching out to your GP or a gastroenterologist for investigations.
How does gut health impact weight?
There is evidence that suggests the types of microorganisms in the gut can be a predictor of your weight, and either support in weight loss, or promote weight gain. For example, one study showed that those with a high level of bacterias known as Prevotella, compared to those in the Bacteroids group, were able to lose weight and body fat more easily compared to humans with a similar gut population of both groups of bacterias.
Certain bacterias have been linked to weight loss and reductions in visceral fat, where as others have been linked to promoting fat storage. In fact, people with obesity have different and often less diverse gut bacteria, compared with those who are not obese. This is even true in the case of identical twins, which indicates that gut bacteria can have a bigger role than genetics, when looking at weight.
It is not completely clear how the microbiome in the gut can influence weight in this way, but we do know that the microbes are heavily involved in balancing blood sugar levels and therefore having a role to play in insulin production, as well as being in control of how we respond to hunger and satiety hormones, that control appetite and how much we eat.
Can gut bacteria influence weight loss?
Bacteria in the gut are involved with digestion and the absorption of nutrients from the foods we eat. Certain bacterias are more efficient at obtaining the energy from food, and people with these types of bacterias absorb a higher amount of calories and energy overall from the same foods, compared to those with a smaller proportion of these bacterias. Specific types of gut bacteria can promote the storage of fat within the body, whereas other types of bacteria can promote fat breakdown as a source of energy.
The bacteria in the gut also influence the hormones that are important in appetite regulation, specifically ghrelin and leptin hormones. Higher levels of ghrelin can stimulate hunger, leading to increased food intake, whereas higher levels of circulating leptin hormone helps to keep us satisfied, reducing food intake.
A diet rich in high fibre foods such as legumes, fruits and vegetables, has been associated with increased diversity of the microbiome, and also reduced weight gain. When these fibres are broken down by the bacterias, they produce short-chain fatty acids (SCFAs), such as butyrate and acetate. These SCFAs are known to influence fat storage and metabolism, as they can increase the feelings of satiety, leading to less food consumed, as well as improving insulin sensitivity, which is important for weight management. SCFAs have a role in reducing inflammation, which is why a high fibre diet is associated with better weight maintenance.
The microbiota are also involved with our immune system and can influence inflammation within the body. Long term inflammation, even low-grade, is associated with obesity – therefore, aiming for a diverse gut microbiome can help to reduce inflammation, support a healthy immune response and possibly aid in weight loss.
How to improve gut bacteria for weight loss?
Adopting specific dietary and lifestyle changes can help to improve the diversity of the gut microbiota, which can support weight loss. This includes:
- Increasing fibre intake:
Aim to add in more plant fibres in the diet on a regular basis. This can range from fruits and vegetables, fresh or frozen or dried, as well as pulses such as beans and lentils. Add in nuts and seeds as these provide fibre, as well as whole grains such as brown rice, oats and quinoa. Focus on slow additions, as if you try to increase the fibre intake too fast, this can be a shock for the body and bacteria, and may lead to abdominal discomfort and constipation. - Include prebiotic rich foods:
Prebiotics are foods that feed the microorganisms found in the gut. Prebiotics are mainly found in fruits and vegetables, as well as spices and herbs. For example, a type of prebiotic fibre known as inulin, is found in oats, onions, garlic and leeks. Other prebiotic rich foods include whole grains and bananas. - Add in fermented foods:
These are foods that are made using microorganisms, usually bacteria or yeast. It has been used as a way of preservation of foods for many years, but research has shown that fermented foods are greatly beneficial for our health. This is because many of these fermented foods contain probiotics, bacteria that help to promote diversity of the gut microbiome and provide health benefits. Fermented foods include live yoghurts, kefir, kimchi, sauerkraut, as well as fermented soy products like tempeh. - Reduce processed foods and sugar:
Regular consumption of foods that are heavily processed or high in added sugar can reduce the diversity of the healthy bacteria in the gut. High sugar intake can increase inflammation throughout the body, not only reducing gut diversity but increasing risk of pro-inflammatory bacteria forming, which can lead to weight gain and several diseases, such as cancer. - Increase exercise frequency:
Taking part in regular movement in the form of both cardiovascular and strength training exercise is associated with improving gut bacteria diversity. This can be due to the link between exercise reducing inflammation, as well as improving the metabolic health and function of the gut microbes. Some research has shown that elite athletes have a higher gut microbial diversity and a higher concentration of species involved in producing SCFA’s, known for their health benefits and links to weight management. - Minimise antibiotic use:
Unless prescribed by your doctor or health care team, avoid the use of antibiotics. This is because the antibiotics can kill not only the harmful bacteria, but also can destroy much of the gut microbiome, including healthy organisms. In fact, antibiotic use is linked to obesity – this is possibly because antibiotics reduce the number of bacteria in the gut that can protect against obesity, and can alter the metabolic signalling pathways.
Best foods for gut health and weight loss
Here you should list the foods, and also explain each food. List them as H3. (I already added a few h3, but feel free to change them or add additional ones). As well near each H3 you should add an image of each food. Also add keywords: gut health and weight loss
Whole grains
Whole grains such as oats, brown rice, barley and quinoa can support the gut health and weight loss, as these foods contain prebiotics, which feed the beneficial bacteria, helping to improve diversity in the gut. Research has shown that this gut diversity can aid in weight management.
Fermented foods
Fermented foods are that which contain live microorganisms. This can help in preserving the food, but also provides health benefits. For example, one study showed that regular live yoghurt consumption was associated with reduced visceral fat levels, and changes in gut microbiome were seen during this time. Another popular fermented food is kefir, and regular consumption of kefir is related to the reduction in obesity and cardiovascular disease. This may be due to the fact that kefir is a fermented drink that provides multiple strains of probiotics. Both live yoghurt and kefir are fantastic incorporated into smoothies, to support gut health. Other popular fermented foods include kimchi and sauerkraut, which contain good sources of fibre and probiotics. Research has shown that kimchi contains benefits to prevent and reduce obesity and associated inflammation, by changing gut microbiota composition, and increasing the rate of SCFA production.
Prebiotic foods
Foods that contain a source of prebiotics include leeks, onion, garlic and banana. Prebiotics are types of fibres, such as resistant starch or inulin, which help to feed the probiotics, or the beneficial bacteria. A randomised control trial study looked at almost 60 overweight young adults, and supplemented them with 14 days of inulin fibre. Results showed an association between the fibre and a reduced response to high calorie food cues related to reward, which further supports the link between probiotic rich food altering gut bacteria balance and supporting weight loss. A review published in 2019 showed that green bananas in particular, which are high in resistant starch fibre, can modify the gut microbiome, insulin metabolism, and have a positive influence on weight management.
Nuts and seeds
Although nuts and seeds may seem high in calories and are often avoided during weight loss attempts, some of the fat is not actually absorbed and will pass through the digestive system, and then excreted. This is because nuts and seeds are high in fibre, and some of the nutrients, including fat, are not absorbed completely in the gut and are instead lost in stool. Snacking on nuts has also been found to reduce appetite, which can influence weight regulation.
Fruits and vegetables
Regular intake of fruits and vegetables can modify gut microbiota, which can support the anti-inflammatory influence of the microbiome and weight. A bigger variety of fruits and vegetables allows for more fibres, which, when digested by the bacteria in the gut, produce SCFAs. These help to control hunger hormones, which in turn can influence weight and appetite.
Polyphenol-rich food
Polyphenols are a type of antioxidant found in plant foods, namely fruits, vegetables, grains, green tea and coffee. High intake of polyphenols is associated with anti-inflammatory effects. They are transformed into metabolites by the gut microbiota, which benefit the human health. The intake of polyphenols has been linked to reducing weight and preventing obesity, through observational studies. Certain polyphenols, including anthocyanins and resveratrol, have been shown to have beneficial effects on lipid metabolism, which may influence weight.
Foods to avoid for better gut health and weight loss
Refined sugar
Refined sugar has been processed in a way to make it into a simple, easily digestible and absorbable form of sugar. Examples include white and brown sugar, palm sugar, corn syrup, coconut sugar, cane sugar and molasses. High and regular intake of refined sugars can disrupt the gut barrier function and lead to increased systemic inflammation and digestive issues. The high intake of sugar can disturb the balance of bacteria, increasing species of Protobacteria, whilst reducing the Bacteroides. The latter helps to break down higher fibre complex carbohydrates, and a reduction in these bacteria can lead to an imbalance, known as a dysbiosis. This in turn can increase the likelihood of weight gain, with the imbalance of healthy gut bacteria.
Artificial sweeteners
Research carried out in rodent studies has shown that artificial sweetener intake can alter the gut bacteria, and lead to weight gain. However, the total volume of sweeteners fed to the rodents are much higher than what we as humans would consume, and we are not the same as rodents! So we cannot draw conclusions from this itself. Human research is much less available, though one study in 120 adults showed that the sweeteners altered stool and oral microbiome, with sweeteners saccharin and sucralose significantly impairing glycemic responses in subjects.
Fried foods
Research in both human and animal studies have shown that frequent fried food consumption, as well as the byproducts produced from frying foods in oil, are linked to the reduction in the diversity of the gut microbiome.
Having a diet high in fried meat products can lower the microbiota richness in the gut, as well as changes in the overall structure and composition of the microbiome. Fried meats have been found to influence pathways related to glucose metabolism, which directly links to blood sugar control in the body. As well as impaired glucose metabolism, increased levels of inflammatory markers have been observed, leading to a rise in systemic inflammation.
Ultra-processed food
Foods are processed in various ways, to help with taste, appearance, shelf life and for other reasons. Ultra-processed foods in particular can contain higher levels of salts, sugars, fats and additives, as well as preservatives, which have been linked to changes in gut health. A diet in highly processed foods is associated with an increased population of ‘bad’ gut microbes, which are linked to negative health consequences. Not only this, but regular consumption of ultra-processed foods has been linked to type 2 diabetes, obesity and certain types of cancers.
Alcohol
Consuming large amounts of alcohol can lead to gastrointestinal damage, as well as promoting intestinal inflammation. This in turn has been linked to chronic disorders including liver disease, GI cancers and inflammatory bowel syndrome (IBS). Regular alcohol consumption induces inflammation, which is linked to a change in the gut microbiota composition. With this change in gut microbiota, there is often an association with an overgrowth of ‘bad’ bacteria, known as dysbiosis. Dysbiosis has been linked to the release of endotoxins released from these bacterias, and it is these endotoxins that activate immune cells, which promote inflammation. Chronic inflammation is linked with weight gain and obesity, as well as development of health disorders such as type 2 diabetes.
Red meat
Regular red meat consumption can increase the production of certain toxins by the gut bacteria. These toxins are linked to a higher risk of cardiovascular death. This is because the heme iron found in red meat can cause harm to the gut microbiota, with a diet rich in red meat and heme iron showing increases in certain bacterias such as Streptococcus bovis, Fusobacterium, Clostridium, and Helicobacter pylori, which are linked to increased risk of colorectal cancer.
Diets for gut health and weight loss
Eating to look after your gut health and expand on the diversity of your gut microbiome can have many benefits, such as improving metabolism and supporting in weight loss. Here are some key tips to follow:
Plant foods
Include a range of plant foods, as these are rich in fibres that can support gut health and microbiome balance. This includes foods such as beans, lentils and other pulses, soy products such as tofu and tempeh, as well as nuts, seeds and whole grains.
Spices
Using a range of spices and herbs when cooking can also help to enchance the quality of the gut microbiome. Try to diversity the spices used when creating meals, and don’t forget about herbs, either fresh or dried, which are also great for gut health.
Probiotics and fermented foods
Including foods which are a source of probiotics into the diet, can help enhance the range and diversity of gut bacteria. For example, foods such as kimchi, sauerkraut, live yoghurt and kefir, are rich in probiotics that can support gut biodiversity.
Here are some example meal plans to support your gut health and aid in possible weight loss:
Example one:
Breakfast – Live Greek yoghurt and kefir smoothie, with berries & walnuts
Snack – Hummus and vegetable sticks
Lunch – Chicken salad with brown rice
Dinner – Lentil and chickpea curry with spinach and quinoa
Example two:
Breakfast – Poached eggs and mushrooms with sourdough
Snack – Wholegrain crackers with smashed avocado and cherry tomatoes
Lunch – Roasted mixed vegetable soup with butter beans, topped with flax seed
Dinner – Spiced salmon with broccoli, roasted sweet potatoes and kimchi
If you would like support with specific meal plans tailored to your needs, working with a private dietitian can support you to find out what is best for your requirements.
Eat The Rainbow diet for better gut health and weight loss
Aim to eat a range of colourful fruits and vegetables throughout the week for optimal diversity in nutrients, which can support gut health and weight loss. Here is an example of how different colours of foods can be added across the week:
Probiotics for gut health and weight loss
Probiotics are microorganisms that are alive, and have health benefits. They are found in certain foods, usually known as fermented foods, as well as supplements. The way that probiotics influence weight isn’t completely clear, though it is thought that the probiotics can influence appetite and energy regulation though short chain acid production. Some probiotics have been linked with reducing the absorption of fat from the diet, leading to an increased fat excretion in the faeces. Probiotics can increase the release of appetite suppressing hormones, such as Peptide YY, as well as promoting a reduction in fat storage. As previously discussed, obesity is linked with inflammation, and improving the gut can reduce inflammation. Probiotics themselves have been linked to a reduction in inflammation, which can therefore have an impact on weight management.
Including prebiotics in the diet can also support gut health and weight. Prebiotics are the food that the microorganisms in the gut feed off from, that we as humans cannot digest. An example of this is fibre, and some examples of prebiotic foods include leeks, onion, garlic, banana and whole grains. A regular intake of both pre and probiotics is linked with a change in gut diversity, allowing the ‘good’ gut bacteria to grow and expand. With a better more diverse gut microbiota, an improvement in the gut lining can be seen, which can reduce systemic inflammation, reducing risk of obesity and other disease.
Supplements that help with gut health and weight loss
Several supplements like HHC gummies are available on the market that claim to support with weight loss and to help with gut health. Here, we explore the most popular and commonly found;
Collagen
Collagen supplementation has become increasingly popular over the years. Collagen is a type of protein found in the body in abundance, in the skin, bones, connective tissues, organs and intestinal lining. It is obtainable from food sources such as chicken, fish, egg whites and bone broth. Supplementation of collagen has found a reduction in bloating and improvement in mild digestive symptoms, as well as improving body composition in overweight individuals, compared to placebo in a 6 week supplementation trial. Though the latter was using a very small sample size of 17 people, and longer term, bigger scale studies are needed. Unfortunately, no good quality evidence is currently available to show that collagen can promote better gut health and long term weight loss in large population groups.
L-Glutamine
L-Glutamine is a type of amino acid, which helps to create protein in the body. It has been connected to gut health and is sold as a supplement with claims to help maintain a healthy gut. Research has shown that glutamine can help sustain the balance of the gut microbiome, can help strengthen the cell barrier and junction proteins of the intestinal lining to reduce damage and leakage, and also reduce the inflammatory response in the gut. It is naturally found in many protein rich food, such as lentils, beans, fish and meat. However, supplementing with L-Glutamine hasn’t proven to be overall beneficial, with one study showing that supplementation increased insulin release, which in turn lead to increased meal sizes.
Green tea
Green tea has been sold as a supplement for gut health and weight loss, as it contains certain active ingredients to support metabolism and break down fat cells. Note that research has been carried out in concentrated green tea supplementation, rather than a green tea drink. To note in particular, green tea has a high concentration of antioxidants, particularly catechins. One of these catechins is known as epigallocatechin gallate (EGCG), which has been researched to help increase metabolism, leading to an improvement in overall calorie burn. Animal studies have shown that EGCG inhibits the enzyme that breaks down the hormone norepinephrine, and when this enzyme is inhibited, the amount of norepinephrine hormone will rise, which can promote fat breakdown. Green tea extracts have also been linked to promoting the growth of particular bacterial species that are found in lean people, which can correct bacterial dysbiosis in obese people, and improve lipid (fat) metabolism, by influencing the growth of specific bacteria that are involved in fat metabolisation. More research is needed to understand the dose benefit and long term changes of supplementing with green tea.
Green powders
Green powder companies have marketed their products to emphasise on the benefits of adding in vitamins, minerals, digestive enzymes, fibres, pre and probiotics, which are all known to be important for gut health. However, for most people, eating a balanced and nutritious diet will provide all of the above through whole food sources, without the need to rely on powders. As well as this, whole food forms of these nutrients are often better absorbed compared to the extracted counterparts found in these powders. Some of these supplements contain high FODMAP ingredients, which can trigger symptoms for those with a sensitive gut. These include ingredients such as chicory root extract, garlic extract and fructooligosaccharides. There is no significant research between green powders and weight loss, and we do not recommend these products unless specifically advised by your healthcare professional.
Having support from a dietitian can help to support your gut health as well as ensuring that you are eating a balanced and well varied diet. Book a consultation with a dietitian here.
