What if the reason you can't lose weight, your energy is inconsistent, and your blood sugar won't budge has nothing to do with discipline — and everything to do with your DNA?

I want to tell you about a client of mine. I'll call her Anna. She's a woman in her late forties — intelligent, health-conscious, motivated. She came to me having gained eight kilograms over the previous year despite, by her own account, eating better than she ever had in her life.

She'd gone keto. Properly keto. She'd done the research, cut the carbohydrates, loaded up on healthy fats, tracked her macros, stayed in ketosis. She was committed.

The weight kept going up. Her energy was inconsistent. Her blood glucose wasn't improving the way keto is supposed to improve it. She was starting to feel like a failure.

She wasn't a failure. The diet was failing her.

The Problem With Diet Advice in 2026

We are living in a golden age of health misinformation dressed up as health information. And the two are often almost impossible to tell apart.

Here's how it plays out. An influencer — an athlete, a podcaster, maybe a well-credentialled doctor — discovers a dietary approach that transforms their health. They lose twenty kilos. Their autoimmune condition goes into remission. Their energy becomes extraordinary. And they are telling the truth. That happened for them.

So they share it. And they should.

But what they almost never say is: this worked for me because of my specific genetics, my hormonal profile, my gut microbiome, my stress history, and about forty other variables I have no idea whether you share.

What they say is: this worked for me. Try it.

And millions of people do. The ones whose biology happens to match get great results — they become the testimonials, the before-and-after photos. The people it doesn't work for quietly disappear, feel like failures, and move on to the next trend.

I've watched this cycle play out across every major dietary movement of the last twenty years. Low fat. High fat. Raw vegan. Carnivore. Paleo. Keto. Intermittent fasting. Every single one has real science behind it. Every single one works brilliantly for some people. And every single one, applied to the wrong biology, is somewhere between ineffective and actively harmful.

The fundamental problem isn't a lack of nutrition science. It's that we keep applying population-level research to individual-level situations.

You are not a population. You are a specific, unique biological system with a particular set of genetic instructions, a particular hormonal environment, a particular gut ecosystem, and a particular history of stress and illness.

Treating you with population-level diet advice is like prescribing the same medication dose to every person regardless of their weight, liver function, or genetic variants in drug metabolism. We wouldn't accept that in pharmacology. We shouldn't accept it in nutrition.

What Anna's DNA Actually Showed

When we ran Anna's comprehensive genetic panel alongside full bloodwork, hormone testing, and a complete microbiome mapping, what we found was extraordinary. For the first time, her body's behaviour made complete sense.

Three variants in her metabolic genes told a very clear story.

PPAR-alpha — The Fat Metabolism Gene

PPAR-alpha is essentially the master regulator of fat metabolism. It governs how efficiently your body uses fat as fuel — particularly saturated fat. Anna carried a variant in this gene specifically associated with abnormal lipid metabolism on high saturated fat diets.

In plain language: the genetic machinery you need to efficiently burn the fats that form the foundation of a ketogenic diet — Anna's was running at significantly reduced capacity.

When you feed a body like Anna's a classic ketogenic diet, even a well-formulated one, the fat doesn't get burned efficiently. It gets stored. Blood lipid profiles can shift in directions that increase cardiovascular risk rather than improving it.

This is the opposite of what keto is supposed to do. And it's directly predicted by this one genetic variant.

ACSL1 — The Saturated Fat and Blood Sugar Connection

ACSL1 is involved in how your body handles saturated fat in relation to blood glucose regulation. Anna carried the homozygous variant — both copies — which is associated with elevated fasting glucose specifically in response to high saturated fat intake.

Here's the cruel irony: Anna went keto partly because she was concerned about her blood sugar. She was trying to protect her metabolic health. But because of her ACSL1 genotype, a high saturated fat diet was actively raising her fasting glucose.

The diet she chose to fix the problem was making it worse.

APOA2 — Body Composition and Saturated Fat

APOA2 is a gene involved in how your body responds to saturated fat in terms of body composition. The variant Anna carried — homozygous — is associated with significantly higher BMI when saturated fat intake exceeds approximately twenty-two grams per day.

To put that in context: twenty-two grams of saturated fat is roughly two tablespoons of butter, or about 150 grams of fatty meat. On a standard ketogenic diet, you might hit that by mid-morning.

The Triple Stack

Here's the critical point: each of these variants individually might be manageable. But when you stack PPAR-alpha, ACSL1, and APOA2 — all three working against saturated fat metabolism simultaneously — the effects compound. They don't just add. They multiply.

Anna wasn't slightly wrong for keto. She was, from a genetic standpoint, one of the worst possible candidates for a traditional high saturated fat approach.

No amount of discipline, tracking, or trying harder would change this. It wasn't a behaviour problem. It was a biology problem.

Importantly, these variants don't mean Anna can't eat fat. They mean she needs the right kinds of fat — predominantly monounsaturated fats from olive oil, avocado, oily fish, and macadamias — rather than the high saturated fat load of butter, cream, and fatty meat that defines classic keto.

Her insulin response genes? Actually quite robust. Her body handles moderate complex carbohydrates well. The diet that fits Anna's genetic blueprint is closer to Mediterranean — quality protein, predominantly unsaturated fats, moderate complex carbohydrates from whole food sources, abundant vegetables. The exact opposite of what she'd been doing for a year.

What the Microbiome Mapping Revealed

This is the layer that most people never look at — even when they think they're doing comprehensive health testing.

Anna's microbiome had some genuinely reassuring findings. Her calprotectin — the key marker of gut wall inflammation — was well within normal range. Her zonulin, which indicates intestinal permeability (leaky gut), was normal. There were no parasites, no H. pylori, no Candida, no pathogenic bacteria. Her pancreatic function was strong.

On the surface? Clean gut. Nothing a standard test would flag.

But when you look deeper at the bacterial ecosystem itself, a very different picture emerged.

The Bifidobacteria Problem

Her total Bifidobacteria count was just six — sitting at the very floor of a reference range that goes up to two thousand. Three of the four key Bifidobacterium species — adolescentis, breve, and longum — were below detectable limits. Only Bifidobacterium bifidum was present, and barely.

This matters enormously. Bifidobacteria aren't just nice to have — they are foundational architects of your gut ecosystem.

Bifidobacterium adolescentis specifically drives GABA production. GABA is your primary calming neurotransmitter. Low GABA means higher anxiety, poorer sleep, and a nervous system that runs hotter under stress. In someone already carrying a significant stress load, this is not a small thing.

Bifidobacterium longum regulates inflammatory cytokines and maintains intestinal barrier function. When it's undetectable, your gut-immune interface is operating without one of its key regulators.

The Lactobacillus Picture

Her Lactobacillus diversity was also poor. L. acidophilus, L. plantarum, L. rhamnosus, and L. salivarius were all below detection threshold or absent. L. rhamnosus is particularly notable — the research is clear that chronic psychological stress is one of the primary drivers of Lactobacillus depletion. Her gut was reflecting the stress load she'd been carrying.

The Clinical Picture

Anna's gut was structurally intact — no inflammation, no infection, no permeability problems. But the population of beneficial organisms living inside it had been depleted, almost certainly by the combination of chronic stress, a high-saturated-fat diet that doesn't selectively feed Bifidobacteria and Lactobacilli, and prolonged physiological strain.

The gut-brain axis runs both ways. A nervous system under chronic stress depletes beneficial gut bacteria. And those beneficial bacteria produce the neurotransmitters and short-chain fatty acids that regulate your stress response. When they're gone, the whole system becomes less resilient.

A high saturated fat ketogenic diet doesn't preferentially feed Bifidobacteria. It actually tends to starve them. Anna's genetics meant the fat wasn't being burned efficiently anyway — so the two problems were compounding each other simultaneously.

The good news: Bifidobacteria and Lactobacillus depletion is highly reversible. These organisms respond well to targeted probiotic repletion and to dietary changes that feed them — diverse plant fibres, resistant starch, polyphenol-rich foods like berries, olive oil, and dark leafy greens. The shift to a Mediterranean dietary pattern that Anna needed for her genetic variants also happens to be precisely the pattern that nourishes Bifidobacteria. The genetics and the gut were pointing to the same solution.

The Hormonal Layer — The Hidden Variable

Anna was post-menopausal and on hormone replacement therapy, but her hormones hadn't been properly optimised. Her SHBG — the carrier protein that binds hormones and makes them unavailable to cells — was elevated, meaning a significant portion of her oestrogen and testosterone was bound and inactive. Her thyroid conversion was suboptimal. Her cortisol rhythm was dysregulated after an extended period of significant loss and grief.

Cortisol at chronically elevated levels drives visceral fat deposition directly. It raises fasting blood glucose. It suppresses gut immune function. And she had genetic variants making her nervous system more sensitive to stress than average — meaning the events of the past year had hit her physiology harder than they would have hit someone with different genetics.

The test I use as my gold standard for hormone assessment is the DUTCH test — Dried Urine Test for Comprehensive Hormones. It gives us not just hormone levels but metabolites — how hormones are being broken down, whether cortisol rhythm is appropriate, whether oestrogen is going down healthy or unhealthy detox pathways. None of this shows up in a standard blood panel.

No diet would have fully worked for Anna without addressing this hormonal environment simultaneously. That's not a lifestyle platitude. That is endocrinology.

What Everyone Should Be Doing — The Universal Principles

There are ground-floor principles that apply to virtually everyone regardless of genetics.

Eliminate processed seed oils. Industrial canola, soybean, sunflower, and corn oils drive systemic inflammation in the quantities embedded in modern food. Cook with olive oil, butter, or ghee.

Eliminate ultra-processed food. Not because calories are evil, but because ultra-processed food is engineered to override your satiety signals and damages your gut microbiome through emulsifiers and additives that don't exist in nature.

Minimise simple carbohydrates and sugar. Not all carbohydrates are equal — as Anna's case shows, some people's genetics favour moderate complex carbohydrates. But no one's genetics make them well-adapted to refined sugar and white flour in the quantities the modern food supply delivers.

Prioritise protein. Across virtually every genetic profile, adequate protein supports muscle maintenance, metabolic rate, satiety, and long-term metabolic health. Most people eat less than they need — particularly women as they age.

Get your omega-3s from food and supplementation. Whether through oily fish two to three times a week or a quality supplement, adequate EPA and DHA supports cardiovascular health, neurological function, and metabolic health.

Eat for your gut. Diverse plant foods, fibre variety, fermented foods, polyphenols. This feeds the Bifidobacteria and Lactobacilli that your stress response, immune system, and metabolism depend on.

These are the universals — the floor. Beyond them, the specific composition of your diet needs to be built for your biology.

What Testing to Consider

If you've been doing the basics right and still not getting results, here's where to start:

A comprehensive blood panel — not a basic GP panel. Full thyroid function including free T3 and reverse T3. Fasting insulin alongside fasting glucose. Full iron studies, homocysteine, sex hormones including SHBG and DHEA. ApoB. High-sensitivity CRP.

DNA nutritional genomics testing — looking at metabolic variants, saturated fat response, carbohydrate handling, detoxification pathways, and hormonal metabolism. Your genes are not your destiny, but they are your tendencies and your optimal fuel types.

DUTCH hormone testing — if you're peri- or post-menopausal, have hormonal symptoms, or if your stress levels have been chronically elevated.

Complete Microbiome Mapping — if you have digestive symptoms, chronic fatigue, brain fog, mood issues, or have been eating well for months without improving your energy.

Organic acids testing — a urine test giving a window into mitochondrial function, gut bacterial activity, neurotransmitter metabolism, and B-vitamin status. One of the highest-yield tests in functional medicine.

And look honestly at your lifestyle variables as data points — sleep quality, actual stress load, physical activity relative to recovery capacity, and circadian eating patterns. These are hard metabolic inputs, not soft lifestyle suggestions.

What Happened to Anna

She shifted to a Mediterranean-style approach — predominantly monounsaturated fats, oily fish twice a week, quality protein at every meal, moderate complex carbohydrates from whole food sources, and a deliberate increase in the dietary diversity her gut bacteria desperately needed.

We optimised her HRT — improved the delivery and ensured her hormones were actually bioavailable rather than bound and inactive.

We also acted on another genetic finding: she carried a variant in a melatonin receptor gene meaning the ten milligrams of melatonin she'd been taking to help her sleep was impairing her glucose metabolism overnight. We dropped it to half a milligram. That alone made a measurable difference.

We added a targeted probiotic protocol to rebuild the Bifidobacterium and Lactobacillus populations — specifically the strains that were depleted. And we addressed the stress and grief directly. Because no protocol works around unprocessed loss. The body holds it, and the gut reflects it.

Within eight weeks her fasting glucose had dropped back into a healthy range. In twelve weeks she had lost four kilograms — not from restriction or suffering, but from her body finally being in an environment it could work with. Her energy was more stable than it had been in years.

"I spent a year thinking I was doing everything right and failing. Now I understand I was doing the wrong thing really well."

That is the difference between generic advice and personalised medicine.

The Bottom Line

Your body is not broken. It is doing exactly what its instructions tell it to do. The question is whether you know what those instructions actually say.

Diet is not one-size-fits-all. It never was. The reason some people thrive on keto and others deteriorate. The reason your friend lost twenty kilos on intermittent fasting and you couldn't get through week two. These differences are not about willpower. They are about biology.

And the extraordinary thing about where we are now is that we have the tools to actually read that biology. DNA testing. Comprehensive bloodwork. Hormone panels. Gut and metabolic markers. We can look inside the instruction manual of your body and understand what it actually needs.

Stop following diet trends designed for someone else's biology. Start building an approach designed for yours.

If you want to work with me you can grab a consultation here

Supporting your gut microbiome and cellular health is exactly where Rejuvenate Pro comes in — our flagship Immune/gut and longevity formula designed to support the immune system and help you age well  shop.lisatamati.com/products/rejuvenate

Lisa Tamati

Longevity specialist, functional health practitioner, and co-founder of Aevum Labs. Host of the Pushing The Limits podcast (461,000+ downloads). Former elite ultra-endurance athlete. Author of 4 books.

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Contact: support@lisatamati.comRejuvenate Pro