In 2005, I attended a nutrition conference in the United States that changed how I thought about clinical practice. The speaker was Robert Crayhon — one of the most rigorous thinkers in functional nutrition at the time. His lecture on biochemical individuality covered ground that I had been circling in my own clinical work for years: that the reason some clients thrive on one approach and deteriorate on another is not only willpower. Part of it is biochemistry — the way their individual biochemistry processes macronutrients, manages cellular energy, responds to stress, and produces and clears hormones and neurotransmitters.
I came back from that conference with pages of notes and a clinical problem that would take me another twenty years to solve properly.
The problem was this: existing metabolic classification systems — and there were several — gave you a type and then gave you a diet template. They were good at categorising people. They were far less good at explaining why someone was that type, how that type interacted with their test results, and what happened when the type appeared to change over time in response to stress, illness, or ageing.
The Metabolic Natures framework is my answer to that problem.
What biochemical individuality actually means
Williams’ point is often cited but rarely followed to its clinical conclusion. If two people sit at the same table and eat the same meal, the metabolic events that follow are not the same — and for blood glucose, insulin and blood fats after identical meals, that is now well documented. How much those differences decide what someone should eat over years is the part that has not been shown.
It is part of why the person sitting next to you can eat twice what you eat and stay lean and clear-headed. The framework’s bet is that some of that pattern can be recognised and worked with. That is a starting hypothesis, and it is treated as one.
The conventional response has been to average it out — to write guidance for the middle of the bell curve and apply it to everyone. That is reasonable public health. It leaves individuals to find out for themselves whether they are near the middle.
The Metabolic Natures framework refuses to average. It starts from the position that your long-standing pattern is real enough to be worth recognising and working from — not that it has been measured, because it has not. That distinction runs through the rest of this article.
Long-standing pattern versus current function — the distinction the framework depends on
Before introducing the six names, there is one distinction the framework depends on completely. An earlier version of this article stated it the wrong way round, and it has been corrected.
It used to say that you have a fixed genetic type, identified from food-response patterns, and a functional type that the labs reveal. The problem with that is set out in Chapter 7 of the book itself: sustained HPA axis dysfunction produces sympathetic indicators on both the questionnaire and the functional tests. If prolonged stress distorts the tests as well, the tests cannot be the window onto constitution that the earlier framing claimed.
The corrected version. Your long-standing pattern is the way you have run for years, across different diets, jobs and life stages. The questionnaire is the closest available proxy for it — a starting hypothesis, not a measurement. Your current function is what your biochemistry is doing now, and that is what the tests describe. Where the two disagree, current function governs the protocol until the constraint clears.
Is any of this genetic? Probably in part — most physiological variation is. But this article previously asserted that inherited SNPs establish a fixed metabolic type, and that claim has been removed rather than softened. No SNP panel has been tested against oxidative or autonomic position, none is used here, and anyone selling you a gene test for your metabolic type is ahead of the evidence.
And "until the constraint clears" only means something if clearing is checkable, so it is. The markers that define the constraint are named in advance, in writing, before the protocol starts, with the change expected and the timeframe. They are retested. Four outcomes are possible, and all four are recorded: the constraint clears and the picture shifts as predicted; the constraint does not clear; the plan was not followed, which is recorded as untested rather than failed; or the constraint clears and the expected shift does not happen. That last outcome is the one that counts against the reading, and two cycles of it mean reconsidering the reading rather than adding another intervention. The full dated correction is here →
The six Metabolic Natures
The framework uses six names. They are not six kinds of person — they are three positions on each of two axes. The two axes are how rich and starchy meals land for you — which the tradition read as oxidation rate, though nothing here measures it — and where your nervous system sits between activation and recovery. You are read on both.
Axis 1 · Oxidative — how meals land. This sets the balance of starch and fat.
Protein is not on this axis: it is set by your body weight and is the same on every plate.
Axis 2 · Autonomic — activation against recovery. This adjusts carbohydrate within the framework the first axis sets, and never sets it.
You get a direction and a strength on each axis, oxidative first. So a reading is oxidative: fast, lean 72%, strength 64% · autonomic: parasympathetic, lean 68%, strength 41% — low strength, with Catalyst · Grounded (low) as shorthand where a short label is needed. A lean under 60% is read as the middle; strength under 50% is reported as low; fewer than 70% of questions answered makes the reading provisional — all three cut-offs judgement, not evidence. Strength works as a gradient within the framework: a strong reading moves further toward its end of the band, and one just over the line barely moves from the balanced framework. See both axes on one page →
What this is, and what the evidence for it actually is
Metabolic Natures is a framework for deciding where to start, not a test result.
What is well supported: people respond very differently to the same meal. One study tracked 800 people across nearly 47,000 meals and found high variability in blood glucose after identical meals DOI; another, of 1,002 UK adults, found the same for glucose, insulin and blood fats — several of its authors work for a commercial nutrition company, which we note as we would for any study DOI.
What is not established: that any one person does better long-term on one particular balance of food. When four named diets were compared for a year, weight loss tracked how well people stuck to the plan (r = 0.60) and essentially not at all which plan it was (r = 0.07, not significant). DOI The balance you can actually sustain is the one that works.
The specific categories are not validated by controlled trials, and we do not claim they are. No trial has tested whether assigning someone to an oxidative or autonomic category, and matching a macronutrient ratio to it, produces a better result. The closest test of that shape of argument is DIETFITS — 609 adults, healthy low-fat against healthy low-carbohydrate, twelve months, a difference of 0.7 kg between arms, and neither a genotype pattern nor baseline insulin secretion predicted which diet suited whom. DOI DIETFITS did not test oxidation rate or autonomic tone, so it is not a direct refutation — but it tested the logic, and the logic did not hold up.
So what are we claiming? That a structured way of recognising your own long-standing pattern, adjusted from what your test findings currently show, gives you an approach you can recognise yourself in and therefore sustain. And one thing more, which is the part that can be wrong: we write down, before your protocol starts, what we expect to change and by when — and we check it at retest. That prediction can come back not met. Nothing else in the framework can.
And what we are not selling. Metabolic Natures recommends no proprietary formula, and no product is required for the method to work. The lineage this framework comes from did the opposite — it defined its own efficacy as depending on a sole-source supplement range. That is named here because the same standard has to apply to a tradition we came from as to one we did not.
What decades of testing changed
When I attended the Crayhon conference in 2005, functional testing was available but not in the form it is today. The DUTCH hormone panel, the GI-MAP, the Organic Acids Test — the versions of these tests that now provide the level of functional specificity that the Metabolic Natures framework depends on were not yet the clinical standard.
What changed everything was being able to set a person’s long-standing pattern — from detailed history, food response and the questionnaire — alongside what their biochemistry is doing now. An Organic Acids Test shows where energy production is under strain. A DUTCH Plus shows not just hormone levels but how they are being cleared. A GI-MAP shows whether digestion is getting in the way. None of it identifies a position; all of it can show what is in the way.
The Metabolic Natures framework is, at its core, clinical pattern recognition used alongside functional lab data. The questionnaire gives a place to start. The testing shows what is in the way now. The programme works out the route, and the written prediction shows whether it worked.
How the programme works in practice
Identifying your Metabolic Nature is the beginning of the process, not the end of it. The clinical work involves three stages.
Stage one: the starting reading. A detailed dietary and symptom history, the food responses you have noticed across your life, and the Metabolic Natures questionnaire give a direction and a strength on each axis. Where the reading is weak or sparse, it is reported that way and held as provisional. Testing is not used to decide your position — no test has been shown to — but it is used in stage two to see whether anything is distorting the reading.
Stage two: Current function. This is where the distinction above becomes practically important. The test data says what your metabolism is currently doing, which may be quite different from your long-standing pattern. Depleted B-vitamins on the OAT. Cortisol dysregulation on the DUTCH. Gut dysbiosis on the GI-MAP suppressing absorption and skewing the picture. These are not separate problems to address later — they are the reason the long-standing pattern is not currently expressing, and where they disagree with the questionnaire they govern the protocol until they clear.
Stage three: Protocol construction. With the starting reading and current function both in view, the dietary structure, supplement framework, lifestyle changes and recovery strategy are built to work together — and what is expected to change, and by when, is written down before it starts. Not a generic healthy eating plan. Not an elimination protocol for its own sake. A plan built for the person in front of us, and checked.
"The same food that gives one person energy will leave another person exhausted. That is not a paradox. It is biochemical individuality, and it is the reason a plan has to be checked rather than assumed."
Why this is not metabolic typing
I am aware that the Metabolic Natures framework will be compared to existing metabolic typing systems. The comparison is reasonable — both start from the premise that people are biochemically individual and that dietary structure should reflect that. But there are meaningful differences.
Earlier systems used testing too — Healthexcel ran its own challenge tests and, where available, hair analysis — but they used them to assign the type. Metabolic Natures uses them to find what is in the way now, and keeps that separate from the long-standing pattern the questionnaire points to. It does not assign a label and leave you with a food list. It uses the reading as the starting point for a structured programme, writes down what should change, and counts it against the reading if that does not happen.
On where this came from. An earlier version of this article said the six names were derived from clinical practice and not from a prior theoretical framework. That is not accurate and it has been corrected. The ideas are inherited and credited — Watson on oxidative rate, Pottenger and Kelley on the autonomic axis, and Wolcott’s Healthexcel system, which combined the two and which I trained in. Healthexcel itself conceded that its own underlying theories were unproven, and nothing here claims otherwise on its behalf. What is independently derived is the questionnaire: the items, their wording, their grouping and their weighting were written from scratch for this practice and are not adapted from any commercial instrument. That is a narrower claim than the one this page used to make, and it is the one that is true.
Metabolic Natures, Volume 1: Your Reading, Your Plate. A structured, testable starting point for how you eat. The evidence sets the rules it can; every plan writes down what should change before you start, so your own results can say no. Paperback · Kindle.
It replaces the earlier book, which described what the questionnaire and the tests measure the wrong way round; the dated correction lists the seven places.
Find your Metabolic Nature
The Metabolic Natures Programme gives you a starting reading on two axes, a personal plate, and a written prediction checked at follow-up. It is also included within the TDG Five-Test Programme.
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