Metabolic Natures — Six Types. One Framework. Test-Confirmed.

The Core Question

Why does every diet work
for someone — but not for everyone?

For decades, the nutrition conversation has been dominated by competing dietary ideologies — low fat, low carb, paleo, ketogenic, carnivore, plant-based. Each has its passionate advocates. Each has its disillusioned failures. And each keeps generating the same pattern: it works brilliantly for some people and makes others feel significantly worse.

This is not a paradox. It is a predictable consequence of applying population-level dietary advice to individuals whose metabolisms operate on fundamentally different principles. The person who thrives on high protein and fat is not the same metabolic system as the person who thrives on complex carbohydrates. The difference is not willpower or adherence. It is physiology.

Metabolic Natures is the framework that makes that physiology legible — and testable. Six distinct metabolic types, each with recognisable physiological patterns and consistent functional test signatures. Not a questionnaire system. A test-confirmed clinical framework built on three decades of practice and the functional laboratory data that was not available to the pioneers who first identified the concept of metabolic individuality.

"The question was never which diet is correct. The question was always which metabolic system it was operating on — and whether those two things were compatible."

Two physiological axes produce six distinct types

Metabolic Nature emerges from the intersection of two independent physiological systems — both of which vary significantly between individuals and both of which are identifiable in functional test data.

Autonomic Nervous System Dominance

The balance between sympathetic (activating) and parasympathetic (restorative) tone. Determines how the body responds to stress, how nutrients are mobilised, and how the digestive system functions. Reflected in calcium:phosphorus ratio, eosinophil:basophil pattern, and cortisol rhythm on DUTCH.

Cellular Oxidation Rate

The speed at which cells convert nutrients to energy via the Krebs cycle and electron transport chain. Fast oxidisers burn glucose rapidly and need fat and protein for metabolic stability. Slow oxidisers process nutrients more gradually and utilise carbohydrates more efficiently. Reflected in Krebs cycle intermediates on OAT and mitochondrial markers.

The Six Metabolic Natures

Six types. Each with a distinct
physiological signature.

NK/1A · Sympathetic Dominant

Kinetic

The fast oxidiser

Burns through glucose and carbohydrates rapidly. Needs protein and fat to maintain metabolic stability — not as a preference, but as a physiological requirement. Carbohydrate-heavy eating produces blood sugar instability, anxiety, and energy crashes. Thrives on dense, rich fuel at regular intervals.

Characteristic signals

Energetic but crashes on carbohydrates
Strong appetite, craves protein and fat
Anxiety, reactivity, sympathetic overdrive
Performs poorly on high-carb or vegan diets
Responds well to ketogenic or carnivore approach

Test signatures: Elevated Ca:P ratio · High CO₂ · Elevated total protein · Lower triglycerides · Elevated cortisol metabolites on DUTCH

GR/2A · Parasympathetic Dominant

Grounded

The slow oxidiser

Metabolises nutrients slowly. Frequently tired, cold, and carbohydrate-dependent — the mitochondrial machinery processes fat inefficiently. Often misidentified as hypothyroid when the real driver is oxidation rate. A high-fat ketogenic approach typically makes this type feel worse, not better.

Characteristic signals

Fatigue, cold, slow to start in the morning
Smaller appetite, prefers lighter meals
Worsens on high-fat, high-protein diets
Benefits from complex carbohydrates
Elevated triglycerides despite low carb intake

Test signatures: Low CO₂ · Depressed Ca:P · Elevated triglycerides · Low DHEA-S · Blunted cortisol curve on DUTCH · OAT: elevated adipate/suberate

CA/2O · Mixed Oxidiser

Catalyst

The mixed type

Neither dominantly fast nor slow. Context-dependent — shifts with stress load, season, and life stage. Highly adaptable in principle but unpredictable in practice. Fails at both extremes: a pure ketogenic approach destabilises blood sugar, a high-carbohydrate approach produces fatigue. Requires precise macronutrient balance.

Characteristic signals

Inconsistent energy — responds unpredictably to food
Neither extreme diet feels right
Highly sensitive to stress-related dietary shifts
Mixed hunger patterns
Feels best with balanced macronutrient ratios

Test signatures: Mid-range Ca:P · Variable CO₂ · Context-dependent blood sugar patterns · Shifting cortisol pattern on DUTCH

EN/1O · Slow Oxidiser · Aerobic

Endurance

The aerobic type

Built for sustained low-intensity output. Thrives on steady-state fuelling and efficient carbohydrate oxidation. Struggles with high-glycaemic loads and erratic eating patterns. Often the athlete who genuinely does well on a predominantly plant-based diet — not because the ideology is correct, but because the physiology is compatible.

Characteristic signals

Good endurance, struggles with explosive intensity
Thrives on steady, moderate eating patterns
Manages well on lower protein intake
Sensitive to glycaemic load and meal timing
Often does well on plant-forward diets

Test signatures: Balanced autonomic markers · Low-normal Ca:P · OAT: efficient fatty acid oxidation · Good mitochondrial function markers

AD/3O · Variable · Stress-Modified

Adaptive

The variable type

Metabolically flexible by constitution but chronically burdened by blocking factors — nutrient depletions, HPA axis dysregulation, gut dysfunction, or toxic load. Looks like a different type depending on which stressor is dominant. The constitutional type is obscured until blocking factors are addressed. Often the most complex to type from questionnaire alone.

Characteristic signals

No consistent dietary pattern produces reliable results
Symptoms shift with stress and life events
Multiple systems affected simultaneously
History of multiple failed dietary approaches
Blocking factors are the clinical priority

Test signatures: Elevated pyroglutamate (OAT) · Disrupted cortisol pattern · GI-MAP pathogenic load · Multiple simultaneous OAT elevations

CB/3A · Parasympathetic · Balanced

Calibrated

The balanced type

Neither extreme. Well-regulated autonomic balance. Responds well to moderate macronutrient ratios with lower overall food density than Kinetic types require. The type that conventional nutrition advice was implicitly written for — which is why it works for some people and not others. Lightest fuel requirements of the six types.

Characteristic signals

Consistent, predictable energy from moderate eating
Smaller appetite relative to body size
Worsens on very high protein or fat intake
Manages well with plant-forward, moderate diet
Responds well to standard dietary guidance

Test signatures: Balanced Ca:P · Normal CO₂ · Regulated cortisol on DUTCH · Balanced autonomic pattern across markers

Test Confirmation

Why questionnaires aren't enough —
and what the tests actually show

Previous metabolic typing systems relied heavily on symptom and food preference questionnaires. These have clinical value as a starting point — but they measure downstream expression, not the underlying physiology. Diet history, stress load, and medication all distort symptom responses. A Kinetic type who has been on a high-carbohydrate diet for fifteen years may no longer respond to food preference questions the way their constitution would suggest.

The three tests that most reliably confirm Metabolic Nature are already part of comprehensive functional assessment. The patterns were always there — the framework makes them legible.

Test Confirmation — What Each Panel Reveals

Blood Chemistry · 46 Markers

The Metabolic Foundation

Calcium:phosphorus ratio reflects autonomic dominance. Bicarbonate and CO₂ indicate acid-base balance linked to oxidation rate. Total protein and albumin reveal catabolic vs anabolic tendency. Triglyceride:HDL pattern maps fat metabolism efficiency. Thyroid function (TSH, Free T4) modifies metabolic rate and can mask constitutional type.

Organic Acids Test · Krebs Cycle

Mitochondrial Oxidation Pattern

Krebs cycle intermediates reveal where energy production is efficient or bottlenecked. Adipate and suberate confirm impaired fatty acid oxidation in Grounded types. Pyruvate and lactate patterns reveal carbohydrate oxidation efficiency. Methylmalonic acid confirms functional B12 status — a Kinetic type confound when depleted.

DUTCH Plus · Hormone Panel

Autonomic and Adrenal Pattern

Cortisol diurnal curve confirms sympathetic or parasympathetic dominance pattern. DHEA:cortisol ratio maps the anabolic:catabolic balance. Total cortisol metabolites reveal overall adrenal output. Oestrogen clearance pathways are modified by methylation status — particularly relevant for Adaptive types where blocking factors shift the constitutional picture.

An Important Distinction

Genetic baseline vs functional expression

Genetic Baseline

Your constitutional Metabolic Nature

There is a genetic foundation to Metabolic Nature — SNPs governing oxidative phosphorylation, beta-oxidation, and the electron transport chain establish baseline tendencies. A constitutionally Kinetic type will always have that as their biological default. This layer does not change with diet or intervention. It is the inherited terrain.

Functional Expression

What blocking factors can mask

Sitting on top of the genetic foundation are functional layers — HPA axis status, thyroid function, mitochondrial efficiency, nutrient cofactor availability, gut microbiome integrity. These can dramatically shift how the underlying type expresses itself. A Kinetic type under severe chronic stress may function like a Grounded type. The Adaptive designation exists for exactly this reason: blocking factors are masking the constitutional picture, and addressing them is the clinical prerequisite to accurate typing.

HPA Axis Dysregulation

Chronic cortisol dysregulation suppresses the very markers — Ca:P ratio, autonomic balance, mitochondrial function — that define Metabolic Nature. A depleted adrenal pattern flattens the metabolic picture and makes constitutional typing unreliable. Address the HPA axis first, then reassess.

Gut Dysbiosis and Permeability

Systemic endotoxaemia from a permeable gut drives chronic inflammation that suppresses anabolic signalling and distorts nutrient absorption patterns. A Kinetic type with significant gut dysbiosis may not absorb or utilise the protein and fat their type requires — mimicking a Grounded presentation until the gut is addressed.

Nutrient Cofactor Depletions

Krebs cycle function requires B vitamins, magnesium, CoQ10, and iron. Depletion of any of these slows oxidation rate regardless of constitutional type — a fast oxidiser becomes functionally slow when cofactors are insufficient. This is why Metabolic Nature assessment is most accurate after nutritional foundations are established.

Subclinical Hypothyroidism

Thyroid hormone is the primary regulator of metabolic rate. A TSH of 4.26 — technically within reference range — slows oxidation, elevates SHBG (suppressing testosterone), and produces fatigue, weight gain, and cold intolerance that mimics Grounded type characteristics in any constitutional type. Thyroid function must be optimised before Metabolic Nature assessment is reliable.

Why does every diet workfor someone — but not for everyone?

Two physiological axes produce six distinct types

Autonomic Nervous System Dominance

Cellular Oxidation Rate

Six types. Each with a distinctphysiological signature.

Why questionnaires aren't enough —and what the tests actually show

Genetic baseline vs functional expression

Why does every diet work
for someone — but not for everyone?

Six types. Each with a distinct
physiological signature.

Why questionnaires aren't enough —
and what the tests actually show