In 37 years of clinical practice, I've worked with hundreds of people who couldn't lose weight despite doing everything right. The diet was clean. The exercise was consistent. The calories were tracked. The willpower was iron. And yet: nothing. Or temporary loss, followed by rapid regain. Or loss in one area of the body and stubborn accumulation in another.

The standard medical response to this situation is to assume the person is wrong about their intake. "You must be eating more than you think." It's the most demoralising thing a practitioner can say to someone who has genuinely, exhaustedly, tried everything — and it's frequently wrong.

The reason the same approach works for some people and fails for others is that weight is regulated by multiple overlapping hormonal systems, not just by caloric arithmetic. When those systems are dysregulated, fat storage becomes the body's default instruction regardless of what you eat. You can't out-calorie a hormonal instruction to store fat. The solution isn't trying harder. It's identifying which system is disrupted — and addressing it specifically.

The five patterns that block fat loss

These aren't theories. They're measurable, testable physiological states that consistently appear in functional laboratory testing when someone presents with genuine weight loss resistance. In most cases, two or three are active simultaneously — they compound each other.

Pattern 01
Insulin Resistance
Insulin is your primary fat-storage hormone. When cells become resistant to insulin's signal, your pancreas compensates by producing more. Chronically elevated insulin tells your body to store fat — especially visceral fat around the abdomen — and simultaneously locks existing fat in storage, preventing it being used as fuel. You can eat in a caloric deficit and still struggle to lose weight if insulin is chronically elevated. The cells simply can't access stored fat efficiently.

The key: fasting glucose can appear completely normal for years while fasting insulin is already significantly elevated. By the time blood sugar rises on a standard test, insulin resistance has typically been present for a decade. The correct test is fasting insulin, not fasting glucose — and it's almost never ordered on a standard panel.
Identified by: Fasting insulin · HbA1c · HOMA-IR calculation · Blood chemistry
Pattern 02
HPA Axis Dysregulation — The Cortisol Pattern
Cortisol is your primary stress hormone. In acute stress, it's essential — mobilising energy, sharpening focus. In chronic stress, it becomes a fat-storage driver. Elevated cortisol specifically promotes visceral fat accumulation (the dangerous abdominal fat), breaks down muscle (reducing metabolic rate), disrupts sleep (which further worsens insulin sensitivity), and drives sugar cravings by raising blood glucose requirements.

The cruel irony: exercise, particularly high-intensity exercise, elevates cortisol. If your stress system is already dysregulated, intense exercise can reinforce the pattern rather than break it. I frequently prescribe less intense exercise — walking, resistance work, nothing that demands significant cortisol release — as the first intervention for this pattern, which is counterintuitive but clinically important.
Identified by: DUTCH Plus diurnal cortisol · CAR (cortisol awakening response) · DHEA-S
Pattern 03
Thyroid Insufficiency
Your thyroid gland sets your basal metabolic rate — the rate at which your body burns energy at rest. Even mild underfunction, well within the "normal" TSH range, reduces metabolic rate by 15–20%. That's the equivalent of running on 80% of your metabolic capacity every single day. Diet and exercise can't compensate for a 15–20% metabolic rate reduction, which is why this pattern produces such frustrating weight loss resistance.

The standard thyroid test checks only TSH — the pituitary signal to the thyroid, not what the thyroid is actually producing or whether that production is reaching cells as active hormone. The relevant markers are Free T4 (storage hormone), Free T3 (active hormone that enters cells and drives metabolism), and Reverse T3 (an inactive form that competes with Free T3). Thyroid conversion from T4 to T3 requires selenium, zinc, adequate ferritin, and healthy cortisol levels. If any of these are compromised — common findings — conversion suffers and metabolic rate drops.
Identified by: Full thyroid panel (TSH + Free T4 + Free T3 + rT3 + antibodies) · Blood chemistry
Pattern 04
Gut Microbiome Disruption
This pattern surprises people the most. Research over the past decade has established that the composition of your gut bacterial population directly affects how your body handles the food you eat. Dysbiotic gut bacteria — the wrong organisms in the wrong proportions — extract more calories from identical food compared to a healthy microbiome. They also impair GLP-1 production: the gut hormone that regulates insulin secretion, appetite, and fat metabolism. Ozempic and Mounjaro work by mimicking GLP-1. A dysbiotic gut is impairing the body's own GLP-1 system.

Gut infections — H. pylori, Blastocystis, Giardia, bacterial dysbiosis — are more common than people realise and often cause no obvious digestive symptoms. But they drive systemic inflammation, which brings us to Pattern 5.
Identified by: GI-MAP DNA-based stool analysis · Food sensitivity panel (IgG)
Pattern 05
Systemic Inflammation
Inflammatory cytokines — signalling molecules your immune system produces in response to chronic threat — block insulin receptors, suppress fat release from adipose tissue, disrupt leptin (the satiety hormone that tells your brain you've eaten enough), and impair thyroid conversion. Chronic inflammation is simultaneously a cause and a consequence of the other four patterns. It creates a self-reinforcing cycle where fat tissue itself produces inflammatory signals, which worsen insulin resistance, which drive more fat storage.

The sources of chronic inflammation are varied: gut infections, food sensitivities creating ongoing mucosal inflammation, poor sleep, chronic psychological stress, environmental toxin burden, and excess body fat itself. Identifying the primary inflammatory driver — not just suppressing inflammation — is what breaks the cycle.
Identified by: hsCRP · Homocysteine · Blood chemistry · GI-MAP · Food sensitivity

Why the same approach works for some and fails for others

A low-carbohydrate diet works brilliantly for Pattern 1 (insulin resistance) because it directly reduces the insulin stimulus driving fat storage. The same diet can worsen Pattern 2 (HPA axis dysregulation) because very low carbohydrate intake elevates cortisol — it's a physiological stressor. Intermittent fasting helps Pattern 4 (gut microbiome) by giving the gut time to clear inflammatory debris. The same fasting protocol can be catastrophic for someone with reactive hypoglycaemia driving Pattern 2. Exercise improves insulin sensitivity in Pattern 1. Intense exercise in the presence of Pattern 2 worsens cortisol and suppresses thyroid, making Pattern 3 worse. You need to know which pattern you're dealing with before you know which intervention to apply.

A client came to me having done two rounds of a very-low-calorie programme. She'd lost weight each time, regained it plus a little more each time. She was tracking 1,400 calories, exercising five days a week, and gaining weight. Her GP had run standard bloods twice. Normal. She'd been told she must be "eating back" her exercise calories without realising.

Testing revealed fasting insulin of 22 μIU/mL with completely normal fasting glucose — significant insulin resistance that no standard panel would flag. DUTCH showed elevated evening cortisol with low morning cortisol — an inverted pattern consistent with prolonged HPA stress. Free T3 was 3.6 pmol/L with TSH of 2.1 — "normal" TSH, impaired active thyroid hormone. Three of the five patterns were active simultaneously. That's why five rounds of "eat less, move more" had produced five rounds of failure.

What investigation actually looks like

The TDG programme approaches weight loss resistance as a clinical investigation, not a diet plan. Five functional tests — advanced blood chemistry, GI-MAP stool analysis, DUTCH Plus hormone testing, Organic Acids Test, and food sensitivity panel — are run simultaneously and read together. The aim is to identify which patterns are active, in what order they should be addressed, and what specific interventions target each pattern in your specific biology.

This produces a very different kind of protocol. Not a generic diet. Not a supplement stack. A sequenced clinical programme that targets the specific physiological barriers to fat loss that testing has identified in your body. When the right barriers are removed, fat loss typically resumes — often without the grinding caloric restriction that characterises failed previous attempts.

The starting point — a free screen

Before committing to the full investigation, the weight loss pattern finder identifies which of the five patterns is most likely dominant in your presentation. It takes three minutes, costs nothing, and gives you an immediate clinical framework for your situation — something more useful than another diet plan.

Find out which pattern is blocking your fat loss
The free 18-question Weight Loss Pattern Finder takes 3 minutes. It identifies your dominant fat loss resistance pattern and explains what's driving it. No email required, results immediate. If the pattern suggests a clinical investigation, the discovery consultation is the next step.
Take the Free Pattern Finder → Book a Consultation
Stephen Duncan
FDN-P · MSc · Edinburgh · 37 Years Clinical Experience
Stephen Duncan is a Functional Diagnostic Nutrition Practitioner and founder of Detective Health. His weight loss methodology is built on five-test functional investigation rather than dietary prescription — because weight loss resistance almost always has a measurable physiological cause. © 2026 Stephen Duncan Nutrition. All rights reserved. The TDG Clinical Framework and Five Fat Loss Resistance Pattern system are proprietary intellectual property of Stephen Duncan Nutrition.