The VSC Clinical Team
For anyone who has spent years doing what they were told would work — eating less, moving more, watching what they ate — and found the scales barely moving, there is a clinical explanation that's often missed.
It's called insulin resistance, and the evidence increasingly points to it as one of the most important — and most under-recognised — drivers of weight gain in adult populations.
It is worth understanding for two reasons. First, because it explains a great deal that the standard advice doesn't. Second, because the interventions that genuinely shift it look rather different from the ones most people are offered.
At a glance
Insulin is the hormone responsible for moving glucose (sugar) from the bloodstream into the body's cells, where it's used for energy or stored for later. Insulin resistance is what happens when the body's cells stop responding to insulin as effectively as they should. The pancreas compensates by producing more insulin. Glucose levels appear normal on standard tests for years, sometimes decades, while underneath, the system is increasingly under strain [1].
The downstream effect is weight gain — particularly around the middle of the body — alongside fatigue, sugar cravings, brain fog, and difficulty losing weight despite genuine effort.
It is not a moral failing. It is a measurable, treatable, biological condition.
What insulin resistance actually is
Think of insulin as a key, and the receptors on your cells as locks. In a normally functioning system, insulin unlocks the cell, glucose enters, energy is produced or stored, and blood sugar returns to baseline.
In insulin resistance, the locks become harder to open. The body responds by producing more keys — more insulin. For a while, this compensates and blood glucose stays within normal range. But chronically elevated insulin has consequences of its own. It signals the body to store fat (particularly visceral fat, the kind stored around organs), increases appetite, disrupts sleep architecture, and over time, exhausts the pancreas's ability to keep producing more [1, 2].
When the pancreas eventually can't keep up, blood glucose levels start to rise. That's when standard diabetes tests pick up an issue. The problem is — by that point, the underlying insulin resistance has often been progressing for years.
Symptoms most patients miss
The textbook description doesn't quite capture what insulin resistance actually feels like to live with. People who have it tend to describe it in patterns:
- Effort that doesn't translate into results. Dietary changes that should be working aren't. Exercise is consistent but the scale doesn't move.
- Fatigue after meals, particularly carbohydrate-containing ones — a drop in energy 30 to 90 minutes after eating, sometimes severe enough to need a nap.
- Sugar cravings that feel more like a need than a want — typically mid-afternoon or evening.
- Weight gain around the middle, even when other parts of the body don't change much. This is the most clinically significant pattern, because central adiposity is closely linked with metabolic risk [3].
- Brain fog and difficulty concentrating, especially in the afternoon.
- Darker patches of skin on the neck, armpits, or groin — a condition called acanthosis nigricans. It isn't always present, but when it is, it's a strong physical sign.
- Skin tags in similar areas, particularly around the neck.
None of these symptoms on their own are diagnostic. Together — and especially in the context of difficulty losing weight despite effort — they are worth a conversation with a clinician.
Who is most likely to develop insulin resistance
There are some populations the evidence consistently flags as higher-risk:
Women with polycystic ovary syndrome (PCOS). Roughly 70% of women with PCOS have insulin resistance, regardless of body weight [4]. PCOS is, in many ways, the most under-recognised driver of insulin resistance in younger women.
Women in perimenopause and post-menopause. The decline in oestrogen during this period contributes to changes in fat distribution and insulin sensitivity that are well-documented in the published literature [5].
Anyone with a family history of type 2 diabetes. Genetic predisposition matters. Family history is a stronger predictor than weight alone for many people.
People with central adiposity — meaning weight stored around the middle rather than distributed evenly. This is both a symptom and a risk factor.
Anyone with disturbed sleep — particularly less than six hours a night, or fragmented sleep from any cause, including sleep apnoea or shift work. Sleep deprivation acutely worsens insulin sensitivity, even in otherwise healthy adults [6].
Anyone under sustained stress. Chronic stress raises cortisol, and chronically elevated cortisol contributes to insulin resistance through several pathways.
If two or more of these apply to you, it is worth raising the question with a clinician.
How insulin resistance is identified
Standard diabetes screening tests — HbA1c and fasting glucose — catch insulin resistance only when it has progressed enough to affect blood sugar regulation. By then, the underlying problem has often been present for years.
A more thorough metabolic assessment will include:
- Fasting insulin (often more revealing than fasting glucose at this stage)
- HbA1c (average blood sugar over the previous three months)
- Fasting glucose
- Lipid profile (triglycerides and HDL ratio are particularly informative)
- Waist circumference (a better predictor of metabolic risk than BMI alone)
- Blood pressure
Some clinicians also calculate HOMA-IR, a derived score from fasting glucose and insulin, which can give a numerical sense of insulin resistance.
If you have had standard glucose tests come back 'normal' but the pattern of symptoms above sounds familiar, ask for a fasting insulin test specifically. It is the most useful single number in identifying insulin resistance at an earlier, more treatable stage.
What the evidence shows actually works
The interventions that genuinely improve insulin sensitivity are well-studied. Three matter most.
1. Dietary pattern (not calorie counting)
What you eat matters more than how much. The pattern most consistently associated with improved insulin sensitivity is broadly Mediterranean: high in vegetables, legumes, fish, olive oil, and whole grains; lower in refined carbohydrates and added sugar; moderate in protein [7]. Lower-carbohydrate approaches also have supporting evidence, particularly for PCOS-related insulin resistance.
What doesn't tend to work as well: standard calorie-restriction diets that don't address food quality, ultra-processed convenience foods, or any pattern that triggers hunger and rebound eating cycles.
2. Resistance training (not just cardio)
This is where most public weight management advice gets it wrong. Muscle tissue is the body's largest insulin-sensitive tissue. Resistance training — strength work with weights or bodyweight — improves insulin sensitivity measurably, often within weeks, even before any weight is lost [8].
Two to three sessions per week, focused on compound movements (squats, deadlifts, presses, rows), is enough to produce meaningful change in most adults. You do not need a gym. You do not need to be young or already fit. You do need to be progressive — adding weight, reps, or difficulty over time.
3. Sleep, stress, and the parts that don't sell books
Sleep duration and quality directly affect insulin sensitivity. Aim for seven to nine hours, and treat sleep as clinically relevant rather than as a lifestyle choice. If you suspect sleep apnoea — loud snoring, gasping in sleep, daytime exhaustion despite sleeping enough — ask for a referral. It is a major contributor to metabolic disease that is consistently under-diagnosed in the adult population.
Stress management is harder to prescribe, but no less important. Chronic stress, through elevated cortisol, undermines every other intervention. Whatever your route — exercise, therapy, time off, better boundaries — it counts as clinical work.
When to see your GP
Book a conversation if:
- You have two or more of the risk factors above
- You have one or more symptoms persisting for months
- You have a family history of type 2 diabetes
- You have PCOS
- You are in perimenopause or post-menopause and noticing changes in how your body responds
- Standard advice has been tried, sustained, and isn't working
A GP can request the relevant tests and refer onwards if needed. NICE NG28, the guideline on type 2 diabetes prevention and management, sets out the framework for identifying and managing pre-diabetes and related conditions [9]. NICE NG246 covers the broader weight management context [10].
A note about clinical care
If your weight has been difficult to shift despite sustained effort, it is worth being assessed for insulin resistance specifically — not just told to keep trying. A consultation that takes a proper metabolic history, looks at the full picture (including PCOS, perimenopausal status, sleep, stress, and previous attempts), and orders the right tests is what evidence-based care should look like.
If you'd like that kind of conversation, our assessment is designed around it — without judgement, and with the time to take your history properly.
We don't ask why. We ask what helps.
Whenever you are ready, we're here.
References
- DeFronzo RA, Tripathy D. Skeletal muscle insulin resistance is the primary defect in type 2 diabetes. Diabetes Care. 2009;32 Suppl 2:S157-163.
- Petersen MC, Shulman GI. Mechanisms of insulin action and insulin resistance. Physiological Reviews. 2018;98(4):2133-2223.
- Després JP, Lemieux I. Abdominal obesity and metabolic syndrome. Nature. 2006;444(7121):881-887.
- Diamanti-Kandarakis E, Dunaif A. Insulin resistance and the polycystic ovary syndrome revisited. Endocrine Reviews. 2012;33(6):981-1030.
- Lovejoy JC, et al. Increased visceral fat and decreased energy expenditure during the menopausal transition. International Journal of Obesity. 2008;32(6):949-958.
- Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. Lancet. 1999;354(9188):1435-1439.
- Estruch R, et al. Primary prevention of cardiovascular disease with a Mediterranean diet. New England Journal of Medicine. 2018;378(25):e34.
- Strasser B, Pesta D. Resistance training for diabetes prevention and therapy. BioMed Research International. 2013;2013:805217.
- National Institute for Health and Care Excellence. Type 2 diabetes in adults: management (NG28). 2022.
- National Institute for Health and Care Excellence. Overweight and obesity management (NG246). 2025.
Frequently asked questions
Can insulin resistance be reversed?
In most cases, yes — particularly if it's identified early. The combination of dietary pattern change, resistance training, improved sleep, and stress management can restore insulin sensitivity meaningfully over a period of months. Reversal becomes more difficult as the condition progresses towards type 2 diabetes, which is one reason early identification matters.
Is insulin resistance the same as pre-diabetes?
Not quite. Insulin resistance is the underlying mechanism; pre-diabetes is one of its consequences. You can have insulin resistance for years before your glucose levels rise enough to meet the pre-diabetes threshold. Most people with pre-diabetes have insulin resistance, but not everyone with insulin resistance has pre-diabetes yet.
What foods should I avoid if I have insulin resistance?
The most consistent evidence points away from ultra-processed foods, sugar-sweetened drinks, and refined carbohydrates eaten on their own (without protein, fat, or fibre to slow absorption). What matters most is the overall pattern of eating rather than any single food. A diet rich in vegetables, legumes, fish, olive oil, and whole grains is consistently associated with improved insulin sensitivity.
How long does it take to reverse insulin resistance?
Measurable improvements in insulin sensitivity can occur within a few weeks of starting resistance training and dietary changes. Substantial reversal typically takes three to six months of consistent change. The exact timeline depends on starting point, age, genetics, hormonal status, and how complete the intervention is.
Can I have insulin resistance with a normal BMI?
Yes, and this pattern is more common than the standard public health messaging suggests. It is sometimes referred to as 'TOFI' — thin outside, fat inside — and describes people who appear lean but carry visceral fat and have impaired metabolic markers. Standard BMI screening can miss this entirely. Waist circumference is often more informative.
Does PCOS always involve insulin resistance?
Not always, but very commonly. Approximately 70% of women with PCOS have insulin resistance, and it is increasingly understood as a central feature of the condition rather than a co-occurring one. If you have PCOS, addressing insulin resistance is often the most useful starting point for managing both the metabolic and reproductive symptoms.
Does cortisol cause weight gain?
Yes. Cortisol is the body's main stress hormone, and chronically raised levels are associated with weight storage around the middle of the body, increased appetite, disrupted sleep, and impaired insulin signalling. Chronic stress contributes meaningfully to insulin resistance through this mechanism.
Does stress make it harder to lose weight?
Often, yes. Chronic stress raises cortisol, and elevated cortisol shifts where the body stores fat, increases hunger signalling, and disrupts sleep — all of which work against weight loss effort. This is why weight management approaches that don't account for stress tend to produce poor long-term results.
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