The Two Bacteria That Change Everything

In over 25 years of integrative practice, the gut microbiome has gone from a niche interest to one of the most researched areas in medicine. And two bacteria in particular have completely changed how I think about weight, inflammation, mood, and hormonal health.

1. Akkermansia muciniphila

This is the one I get asked about most. You may have heard of it, it’s been called a “keystone” strain because of the outsized role it plays in gut barrier integrity, metabolism, and inflammation.

Its name literally means lover of mucin, and it lives in the mucus lining of your intestine, feeds on it, and signals your gut cells to keep regenerating that protective layer. When it’s thriving, your gut lining stays strong, inflammatory compounds stay out of your bloodstream, and your metabolism works as it should.

When it’s depleted, which research consistently shows is the case in people with obesity, insulin resistance, and metabolic dysfunction, the picture looks very different. The gut lining thins. Inflammation creeps in. Fat storage increases. 

A 2025 Nature Medicine randomised controlled trial confirmed that supplementing with pasteurised Akkermansia improved weight loss maintenance and metabolic health, particularly in people who started with low levels.

Here’s what makes it tricky: you cannot get Akkermansia from food. It doesn’t live in fermented foods. You can’t eat your way to it directly. What you can do is create conditions in which it thrives, and I’ll come to that.

2. Lactobacillus reuteri

If Akkermansia is the gut barrier guardian, L. reuteri is the emotional bridge.

This strain does something remarkable: it works at the intersection of physical health and emotional wellbeing. Recent clinical trials have found that L. reuteri supplementation not only supports weight loss and improved body composition, it also simultaneously reduces anxiety and depression symptoms and improves sleep quality.

That’s not a coincidence. That’s the gut-brain axis in action.

Why Stress Is the Hidden Saboteur

Here’s the part that doesn’t get talked about enough.

Most weight and gut conversations focus on food. But in my clinical experience and now backed by a growing body of research, stress does as much damage to your microbiome as a poor diet.

This is the cycle I see again and again: Chronic stress → depletes beneficial gut bacteria → raises cortisol → drives insulin resistance → increases fat storage → worsens dysbiosis → more stress.

It doesn’t start with food. It often starts with years of pushing through, not sleeping enough, carrying too much, and running on adrenaline.

Psychologically, there’s another layer. Unresolved emotional patterns, anxiety, perfectionism, the body in constant “doing” mode, dysregulate the HPA axis (your stress-hormone system).

That dysregulation directly depletes Lactobacillus species, thins the gut mucus layer, and creates an inflammatory environment where beneficial bacteria simply cannot survive.

This is why I work the way I do. Nutrition alone won’t fix a gut that’s being continuously undermined by a dysregulated nervous system. And the nervous system works alone won’t repair a microbiome that’s been depleted by years of inflammatory eating.

You have to address both at the same time.

The Hormonal Layer: What No One Tells Perimenopausal Women

If you’re in your 40s or 50s, there’s another piece that makes this even more important. As oestrogen declines during perimenopause, the gut microbiome shifts, often significantly. Oestrogen actually supports microbial diversity and helps maintain the gut lining. 

As it falls, you lose some of that protection. Akkermansia levels drop. Inflammation rises. And what was previously manageable, a bit of stress, some poor sleep, a few less-than-ideal food choices and suddenly starts to land very differently in the body.

This is why many women tell me, “I haven’t changed anything. But everything has changed.”

The weight that settles around the middle, the brain fog, the bloating, the disrupted sleep, the mood swings, these are not separate symptoms. They are the downstream effects of a microbiome under pressure, a nervous system in overdrive, and a hormonal system in transition. All at once.

The Hormonal Layer: What No One Tells Men Either

For men in their 40s and 50s, the picture is just as real, it just rarely gets talked about. As testosterone gradually declines through midlife, so does the microbial diversity that supports it.

Testosterone and the gut microbiome have a bidirectional relationship: healthy bacteria help regulate testosterone production, and adequate testosterone helps maintain the bacterial strains that keep inflammation low and metabolism efficient.

When chronic stress enters the picture, and for men in this life stage, it almost always does, cortisol rises, testosterone drops further, and the gut pays the price.

Add alcohol, which is how many men manage stress without realising it, and you have a direct pathway to dysbiosis, visceral fat accumulation around the middle, low energy, disrupted sleep, and a quiet but significant mood shift that often goes unacknowledged.

The belly that appears in a man’s mid-forties is not simply about diet or lack of exercise. It is a hormonal and microbial story,  cortisol dominance, testosterone decline, depleted Akkermansia, and an inflammatory gut environment, all reinforcing each other.

The good news is that this system responds quickly when you give it the right conditions. The same keystone bacteria, the same anti-inflammatory nutrition, the same nervous system support, it all applies equally. 

What Helps

So what does rebuilding look like? Here’s what the research and my clinical experience point to:

Feed Akkermansia indirectly:

Pomegranate, cranberries, blueberries, green tea, dark grapes, garlic, leeks, onions, and chicory root all create the environment Akkermansia needsto grow.

A 12–14 hour overnight fasting window also supports mucus renewal and encourages its growth. If levels are very low, pasteurised Akkermansia supplements are now clinically available and studied.

Rebuild L. reuteri:

Unlike Akkermansia, L. reuteri can be introduced through high-quality targeted probiotic supplements, ideally alongside dietary support and nervous system work, for the best outcomes.

Calm the HPA axis, which means addressing the emotional layer: 

This is where acupuncture enters in a way that might surprise you. Research published in Frontiers in Microbiology (2025) shows that acupuncture at specific points — ST25 and ST36 — directly modulates gut dysbiosis and suppresses the stress-signalling molecules that inflame the gut lining.

Acupuncture also supports vagal tone, and a well-functioning vagus nerve is one of the most powerful anti-inflammatory tools your body has.

Work with the emotional patterns underneath:

Using IFS (Internal Family Systems) and EMDR, we look at the parts of you that have been running on overdrive, carrying stress in the body, using food to self-regulate, or simply never learned to rest.

These aren’t “mindset” conversations. They are direct interventions that change the biochemical environment of your gut.

Nutritional support that goes beyond “eat clean”:

Protein, good fats, prebiotic fibre from vegetables, structured in a way that reduces the glycaemic load, supports the gut lining, and gives your microbiome the raw materials it needs to regenerate. Not restriction. Nourishment.

This Is What Integrative Means

When we stop asking “what’s the problem?” and start asking “what does this body need, all of it, at once?”

If any of this resonates , if you’ve been doing the right things and still not shifting, or if you suspect the stress and hormonal layer is part of your picture, I’d love to talk.

I offer a free 15-minute discovery call where we can look at what might be going on for you specifically, and whether working together makes sense.

Book your free discovery call here

With warmth,

Isabel Flow in Nature | Integrative Health | Northern Beaches, Sydney

Chinese Medicine · Acupuncture · Psychotherapy · Clinical Nutrition

Recipe Idea

Microbiome Reset Breakfast Bowl

A polyphenol-rich bowl to nourish your gut, calm inflammation,

and support weight and hormonal balance

Serves 1 · Prep time 5 minutes · No cooking required · Best at least after a 12-14-hour overnight fast

INGREDIENTS

150 ml — full-fat milk kefir — multi-strain, refrigerated (see note below)

80 g — frozen wild blueberries, or fresh

40 g — pomegranate seeds

40 g — raspberries, fresh or frozen

1 tbsp — chia seeds

1 tbsp — ground flaxseed

20 g — walnuts, roughly broken (approximately 7 halves)

15 g — raw almonds, sliced or whole (approximately 12)

1 tsp — chicory root granules or inulin powder

1 tbsp — raw cacao nibs

1 tsp — raw honey — optional

4 g — fresh mint leaves to finish

METHOD

Step 1 — Prepare the kefir base

Pour 150 ml full-fat kefir into your bowl. If it is quite thick, thin slightly with a small splash of cold water. It should be pourable but creamy; this is your probiotic base.

Step 2 — Stir in the prebiotic powders

Stir 1 tsp chicory root or inulin powder and 1 tbsp ground flaxseed directly into the kefir. Let it sit for 2 minutes. This allows the flax to thicken slightly and the inulin to dissolve. Both are prebiotic fibres that directly feed Akkermansia muciniphila and Bifidobacterium.

Step 3 — Build the bowl

Arrange the blueberries, pomegranate seeds, and raspberries over the kefir base. Scatter the walnuts and almonds across the top, then sprinkle the chia seeds and raw cacao nibs over everything.

Step 4 — Finish and serve

Drizzle with raw honey if using. Finish with fresh mint leaves. Eat slowly and without distraction, vagal tone is supported by a calm, parasympathetic mealtime state. This bowl is medicine. Treat it that way.

WHY EACH INGREDIENT

Kefir

Live multi-strain probiotics including Lactobacillus species, your microbiome foundation.

Pomegranate and berries

Ellagitannins and anthocyanins that directly stimulate Akkermansia muciniphila growth.

Chicory root or inulin

Prebiotic fibre that feeds Akkermansia and Bifidobacterium, the two keystone weight and mood bacteria.

Ground flaxseed and chia

Omega-3 and soluble fibre that support and rebuild the gut mucus layer.

Walnuts

Polyphenol-rich and anti-inflammatory for the support of overall microbiome diversity.

Raw cacao nibs

Potent polyphenols that selectively feed beneficial bacteria over harmful strains.

Raw honey

Small amounts provide oligosaccharides that nourish good bacteria, use them minimally.

NOTES

Choosing your kefir

Look for refrigerated, traditionally fermented, multi-strain kefir. In Australia, good options include Babushka’s Kefir, Impressed Kefir, or Jalna bio-dynamic kefir. Avoid shelf-stable or UHT versions; the live cultures are largely destroyed in these. For Lactobacillus reuteri specifically, consider adding a BioGaia L. reuteri supplement alongside this bowl, as this strain is difficult to source in commercial kefir.

Make it dairy-free

Substitute with coconut kefir, look for a multi-strain version from a health food store. The polyphenol and prebiotic elements remain just as effective.

Best eaten

In the morning, after an overnight fast of at least 12-14 hours. This is when Akkermansia muciniphila is most receptive to nourishment. Sit down, take your time, no screens. This is medicine.

Protein note

This bowl provides approximately 12 to 14 g of protein. If you are using this as part of a metabolic reset program, pair it with a clean whey protein shake on alternate mornings (Option B) to ensure you are reaching your daily protein target of 100 to 115 g.