Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
If you’ve ever felt like you’re doing everything ‘right’ but the scale won’t budge, your gut might be part of the reason. While we often focus on calories and workouts, what’s happening in your digestive system could be quietly shaping your results.
Emerging research shows that the balance of bacteria in your gut plays a key role in how your body processes food, manages cravings, and stores fat. One study suggests that gut microbes may even manipulate eating behaviour to support their own survival, sometimes at the expense of your health, by influencing cravings, mood, and hunger signals.
In this blog, we’ll explore how gut health can influence weight loss and which foods support a healthier gut from the inside out.
Our gut is home to trillions of microorganisms, mainly bacteria, that make up what's called the gut microbiome. While the word ‘bacteria’ might sound negative, many of these microbes are actually beneficial and essential to your health.
Gut bacteria help break down food, absorb nutrients, and even produce certain vitamins. They also play a big role in regulating your immune system and keeping inflammation in check. When your gut microbiome is balanced, your body tends to function more efficiently, including how it digests food and manages weight.
But when there’s an imbalance, meaning too many harmful bacteria and not enough of the good kind, it can affect everything from your energy levels to how your body stores fat. That’s why taking care of your gut is more important than most people realise.
A balanced and diverse gut microbiome begins with proper nutritional support. Certain foods act like fertiliser for your good bacteria, helping them grow and thrive. Fermented and fibre-rich choices are especially beneficial, as they support digestion and overall gut function.
Add more of these gut-friendly foods to your diet:
Yoghurt – Rich in probiotics that replenish good bacteria.
Garlic – Contains prebiotics that feed beneficial microbes.
Onions – Another great source of prebiotics to support bacterial balance.
Asparagus – High in inulin, a type of fibre that nourishes gut bacteria.
Bananas – Especially when slightly underripe, bananas support gut health with prebiotic fibre.
Apples – Contain pectin, a fibre that promotes healthy digestion.
Oats – Full of beta-glucan, which helps beneficial bacteria flourish.
Barley – A whole grain that supports gut health with its fibre content.
Chia seeds – Packed with soluble fibre to aid digestion and bacterial diversity.
Almonds – Provide prebiotic fibre and healthy fats.
Green tea – Contains polyphenols that encourage good bacteria to grow.
Olive oil – Supports anti-inflammatory gut bacteria and overall gut balance.
Just as some foods support your microbiome, others can throw it off balance. Diets high in sugar, saturated fats, and processed ingredients can reduce the diversity of good bacteria and increase inflammation in the gut.
Try to limit these foods where possible:
Sugary snacks and drinks – Feed harmful bacteria and promote imbalance.
Artificial sweeteners – May disrupt microbial activity and gut signals.
Processed meats – Contain preservatives that can negatively affect gut health.
Fried foods – Often high in unhealthy fats that encourage inflammation.
Refined grains (like white bread and white rice) – Lack the fibre needed to support good bacteria.
Excess alcohol – Can reduce microbial diversity and weaken the gut lining.
High-fat fast food – Often promotes the growth of less beneficial bacteria.
Preservative-heavy packaged snacks – Contain additives that may disrupt the microbiome.
Soda and sugary beverages – High sugar content encourages harmful bacterial overgrowth.
Excess red meat – May alter gut bacteria in ways linked to inflammation.
By making mindful food choices, you can help your gut bacteria thrive and support your overall health and weight loss efforts in the process.
Your gut does more than just digest food. It plays a surprisingly important role in how your body manages weight. A healthy gut microbiome helps regulate key processes like metabolism, appetite, and fat storage. When your gut bacteria are in balance, your body is better equipped to absorb nutrients, control cravings, and maintain steady energy levels.
On the other hand, an imbalanced gut, which is often caused by poor diet, stress, or antibiotics, can lead to inflammation, digestive issues, and disrupted hunger signals. All of this can make it harder to lose weight, even if you're eating well and staying active. Research shows that stress alone can reshape the gut microbiome and influence eating behaviour through complex gut-brain interactions.
In short, gut health isn’t just a digestion issue; it’s a weight loss factor, too. That’s why focusing on your microbiome could be the boost your weight loss journey needs.
Below are seven key ways a healthy gut can positively impact weight loss and why nurturing your microbiome might be just as important as your workout routine.
A healthy gut helps break down food more efficiently, which makes it easier for your body to absorb essential nutrients. When your digestive system runs smoothly, you’re more likely to get the vitamins, minerals, and energy you need, without the bloating or discomfort. According to studies, what you eat and how it interacts with your gut bacteria can make a big difference in how well you digest food and absorb nutrients, which sets the stage for better health and easier weight management.
An imbalanced gut can lead to excess gas, bloating, and fluid buildup, making you feel heavier than you actually are. Research has linked gut dysbiosis to issues like small intestinal bacterial overgrowth (SIBO) and malabsorption, which can cause discomfort, poor nutrient absorption, and that bloated, heavy feeling.
A healthy gut, on the other hand, supports smoother digestion and reduces inflammation, helping your body release excess water and feel lighter overall. This not only improves comfort but can also make your progress more visible.
Your gut plays a key role in regulating hormones like ghrelin and leptin, which control hunger and fullness. Studies have found that certain gut bacteria produce metabolites that influence ghrelin signalling, one of the body’s key appetite hormones, through the gut–brain axis. When your microbiome is balanced, these hunger signals become more accurate, helping you feel satisfied without overeating.
A healthy gut can also reduce cravings for sugar and processed foods by influencing brain-gut communication and blood sugar stability. This makes it easier to make healthier food choices and stay on track with weight loss.
Chronic inflammation can interfere with weight loss by disrupting metabolism and increasing fat storage. A healthy gut helps keep inflammation in check by supporting immune system balance and producing anti-inflammatory compounds. In fact, certain gut microbes generate metabolites, like short-chain fatty acids and tryptophan derivatives, that help regulate immune responses and reduce inflammation throughout the body. When your gut is in balance, your body is better able to manage stress, recover from exercise, and burn fat more efficiently.
When your gut is healthy, it supports more efficient energy use from the food you eat. Some beneficial bacteria produce short-chain fatty acids, the by-products of fermenting dietary fibre, which have been shown to help regulate metabolism and promote fat burning instead of fat storage.
As your gut becomes more balanced, your metabolism can work more smoothly, giving you a steady, natural energy boost throughout the day. This can make it easier to stay active, reduce fatigue, and maintain momentum on your weight loss journey.
A healthy gut helps keep your digestive system moving smoothly. Having a healthy balance of gut bacteria and eating enough fibre promotes smoother digestion and regularity.
Research has shown that disruptions in the gut microbiome are strongly linked to constipation, often due to reduced levels of beneficial bacteria that support gut motility. This not only prevents bloating and discomfort but also helps your body eliminate waste more effectively, an often-overlooked factor in feeling lighter and supporting overall weight management.
Your gut and brain are closely connected through the gut-brain axis, meaning your microbiome can influence how you feel both mentally and physically. A balanced gut helps regulate mood-related hormones like serotonin and cortisol, reducing stress levels and promoting emotional stability.
Research highlights that this gut-brain connection plays a significant role in managing anxiety, depression, and stress through pathways involving inflammation, hormone signalling, and neurotransmitter modulation. It also supports better sleep quality through the production of compounds like melatonin, GABA, and short-chain fatty acids, all of which contribute to restful sleep and overall wellbeing. When you're well-rested and less stressed, you're more likely to make healthier choices and keep your metabolism functioning properly.
Your gut may not be the first thing you think of when it comes to weight loss, but it should be part of the conversation. From supporting digestion to regulating hunger and reducing inflammation, your gut microbiome influences many of the processes that affect how your body manages weight.
Improving your gut health doesn’t require a complete overhaul—just small, consistent choices. Eating more gut-friendly foods, cutting back on what harms your microbiome, and paying attention to how you feel can all make a difference.
So if weight loss has felt harder than it should, your gut might be the missing link.
Wondering if your gut health is holding back your weight loss? Explore Why Do I Gain Weight In My Stomach Only? to uncover how an imbalanced gut microbiome may be driving stubborn belly fat, and what you can do about it.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.