4 popular diet trends that could be damaging your gut

From keto and carnivore to intermittent fasting, diet trends seem to dominate social media feeds. Many promise rapid weight loss, improved energy, or better health, often attracting millions of followers looking for quick results without medical guidance or an understanding of which foods we actually need.¹

While some people may benefit from certain dietary approaches under professional guidance, many popular diets have one thing in common: they significantly restrict the variety of foods we eat.

Nutritional experts generally advise that a well rounded, balanced diet is the most effective and sustainable approach to achieving and maintaining good health. However, modern food trends tend to lean very heavily on restricting whole food groups!

That’s important because your gut microbiome thrives on diversity. The trillions of bacteria living in your digestive system rely on a wide range of fibres, plant compounds and nutrients to stay balanced and resilient. When entire food groups are removed, your gut bacteria may have fewer resources to work with.²

Research increasingly suggests that dietary diversity is one of the most important factors influencing microbiome diversity – and a diverse microbiome is associated with better digestion, immune function and overall health.³

Let’s take a look at how some popular diet trends may affect your gut…

1. Keto: What happens when fibre intake falls?

The ketogenic diet emphasises high fats and very low carbs, reducing your intake of fibre-rich foods like fruits, grains, and legumes. This reduction can lead to a decline in bacteria that benefit from complex carbohydrates, such as Bifidobacteria.⁴ This decreases microbial diversity and can lead to inflammation, disrupting digestion.

2. Carnivore diet & loss of plant-based food sources

The carnivore diet involves eating various meats as well as animal product, such as eggs and butter. The diet eliminates plant foods and deprives your gut of certain fibres and polyphenols that are key for supporting beneficial bacteria.⁵ Over time this leads to a less diverse microbiome, and a reduction in bacteria that help produce important nutrients and short-chain fatty acids (SCFAs).

3. Intermittent fasting: Benefits & trade-offs

Intermittent fasting has attracted significant research interest and may offer benefits for some people. However, meal timing is only one piece of the puzzle. The foods consumed during eating windows still play a major role in shaping the microbiome. If fasting results in reduced dietary variety or inadequate fibre intake, microbiome diversity may suffer over time. Sudden and prolonged fasting can also cause destabilising fluctuations in your microbiome, potentially impairing digestion and immune function.⁶

4. High-protein & fat diets & dysbiosis

Diets that rely on meats and fats can increase the protein-fermenting bacteria such as clostridium species. Excessive protein fermentation can produce compounds such as ammonia and phenols, which may irritate the gut lining.⁷ There is a higher risk if fibre intake is too low, so balancing protein with fibre-rich plant foods can lower these effects.

The biggest risk…

By their very nature, many modern diet trends are restrictive, eliminating entire food groups. This can lead to a lack of variety in essential nutrients, which then reduces the richness and resilience of your microbiome. A less diverse microbiome struggles to inhibit pathogens, recover from disturbances, and support your overall health.⁸

Broad & balanced

The healthiest diet is not necessarily the most restrictive one. While different dietary approaches may suit different individuals, research consistently highlights one common theme: diversity matters.

A varied diet provides a wider range of fibres, polyphenols, vitamins and minerals, helping to support a more diverse and resilient microbiome.

Here are six simple ways to support gut diversity:

Eat a rainbow of fruit and veg throughout the week to get your essential nutrients and fibre.
Include whole grains like oats, brown rice, and quinoa for steady energy and good digestion.
Rotate good-quality protein sources, including fish, legumes, nuts, seeds and lean meats, to support muscles and hormones.
Choose healthy fats from foods like avocados, olive oil, and fatty fish to maintain healthy cholesterol levels, reduce systemic inflammation, and improve nutrient absorption.
Limit highly processed foods and added sugars.
Eat fermented foods like kefir, yoghurt, sauerkraut, and kimchi to boost beneficial gut bacteria and improve digestion.