‘Insulin resistance is the major determinant of cardiovascular disease in overweight/obese individuals’ (Reaven, 2005); ‘if more physicians understood that insulin resistance is a huge risk factor for ischemic heart disease, we could potentially do more to motivate our patients’ (Bertsch and Merchant, 2015); and Noakes and Sboros (2017) cite Reaven (2012) that ‘the six conditions most likely caused by high-carbohydrate diets in those with insulin resistance are obesity; arterial disease, both local (heart attack or stroke) and disseminated (type-2 diabetes); hypertension; non-alcoholic fatty liver disease (NAFLD); cancer; and dementia (Alzheimer's disease, also known as type-3 diabetes).’
Yet ‘insulin resistance is the epidemic you may have never heard of’ (Bikman, 2020: 3).
What is insulin resistance?
Insulin resistance is a reduced response to the hormone insulin (Bikman, 2020: 6), with insulin resistance a key component of metabolic syndrome (Gallagher and LeRoith, 2020). In metabolic syndrome the patient must have two of either hypertension, dyslipidaemia, central obesity, or low concentrations of urinary protein; and second, the patients must have insulin resistance (Bikman, 2020: p81).
Somerset GP Dr Campbell Murdoch has a special interest in metabolic health, is a clinical advisor to the Royal College of General Practitioners (RCGP) and co-founder and medical director of preventative healthcare organisation Health Results (https://healthresults.com/about). Dr Murdoch told Practice Nursing that when a person with insulin resistance eats food that raises their blood glucose, ‘huge amounts of insulin are released to try to maintain a normal blood glucose concentration. Those wanting to lose weight should note that insulin is also a fat storage hormone preventing the body from releasing and burning fat for fuel. People gain body fat and struggle to lose it because of insulin resistance and high insulin concentrations.’
Insulin resistance in nursing practice
‘Practice nurses,’ says Murdoch, ‘have a major role in treating patients with long-term conditions, and insulin resistance impacts many with long-term conditions and associated conditions like prediabetes, T2D, hypertension, stroke, heart disease, heart failure, dementia, some cancers, polycystic ovary syndrome, erectile dysfunction, NAFLD, arthritis, leg oedema, some neurological conditions and mental health problems.’
In a COVID-19 context, Demasi (2021) comments: ‘Two-thirds of people in the UK who have fallen seriously ill with COVID-19 were overweight or obese … [and while] … the pathophysiology of COVID-19 is multifactorial, insulin resistance is among the strongest determinants of impaired metabolic function.’ Scotland-based South African Dr Estrelita van Rensburg - a medical virologist who has researched the role of nutrition in metabolic health - explains that ‘COVID-19 has highlighted certain subgroups of people who become severely ill with a higher mortality rate than the rest of the affected population: those with lifestyle diseases like obesity, diabetes and heart disease.’ These conditions, note van Rensburg and Warrack (2020), are the tip of an iceberg of diseases related to our modern-day diet of which most people, including the medical community, are mainly unaware.
Diagnosing insulin resistance
How is insulin resistance diagnosed? ‘Since the 1990s,’ explains Murdoch, ‘it's been known that raised triglycerides, low HDL-cholesterol, raised fasting glucose, raised blood pressure, and increased waist circumference indicate insulin resistance. The string-test provides a rough estimate: cut some string equal to your height, wrap it around your waist near your belly button, and if you can't wrap it around your waist twice you may have insulin resistance.’
Meeting the challenge of insulin resistance
‘Ultra-processed food and sugar,’ says Murdoch, ‘are probably the biggest contributors to insulin resistance. In someone with insulin resistance, carbohydrates - especially refined starches like breakfast cereals and bread - exacerbate the problem, since starches break down to glucose, raising blood glucose, and thus insulin concentrations.’
To address the challenge of insulin resistance, Murdoch comments that a key role for nurses is to understand the nature of insulin resistance and how to recognise it: ‘Since obesity is a consequence and not the problem, discussing insulin resistance need not create concerns about offending a patient with obesity. Nurses need to help patients know how they can improve their insulin resistance. Significant improvement in insulin resistance can be achieved within weeks, leading to reversal of T2D and prediabetes, shrinking waistlines, lower blood pressure, happier appreciative patients, and more Quality and Outcomes Framework points.’
Improving insulin resistance
Murdoch emphasises that central to improving insulin resistance is minimising intake of ultra-processed foods, sugar and refined carbohydrates that digest down into even more glucose: ‘The more insulin resistant someone is, the more their carbohydrate intake and therefore glucose load should be limited. They should focus on eating adequate protein, non-starchy vegetables, and not fearing fat. However, it can be challenging to change habits, navigate our junk food environment, deal with cravings, and accommodate life's complications. But focusing on what matters to the patient and noticing the results will make it easier and worthwhile. GPs and nurses across the UK are seeing their patients' health improve.’ However, noting that ‘primary care clinicians need to be competent to adjust diabetes medications appropriately in individuals who follow a low-carbohydrate diet’, Murdoch et al (2019) explain how this can be accomplished safely.
‘The string-test provides a rough estimate: cut some string equal to your height, wrap it around your waist near your belly button, and if you can't wrap it around your waist twice you may have insulin resistance.’
Southport GP Dr David Unwin - a long-term exponent of how such an approach can benefit patients living with diabetes, while saving on diabetes drug-related expenditure - is the RCGP National Champion for Collaborative Care and Support Planning in Obesity and Diabetes; RCGP clinical expert in diabetes; 2016 NHS Innovator of the year 2016 research; and 2018 winner of the Diabetes UK Primary Care Poster Award. Aware that the term ‘glycaemic index’ (GI) was unclear to many health professionals and patients in relation to blood glucose concentrations, Unwin et al (2016) clarified how people living with T2D understood the importance of the GI. They reinterpreted the GI using a ‘teaspoons of sugar equivalent’ - for example, a 150g bowl of boiled rice can affect blood glucose to approximately the same extent as ten teaspoons of table sugar! Their clinic also recorded significant improvements in quality markers for diabetes and obesity such as HbA1c and weight for those patients prepared to reduce their dietary carb intake. The practice demonstrated superior diabetes control compared to the average for the surrounding area; a lower prevalence of obesity; and saved £40 000 annually on diabetes-related drugs (Unwin et al, 2016).
Updating Practice Nursing, Unwin explained: ‘For nine years we've offered a low-carb dietary option to our T2D patients interested in using lifestyle medicine instead of lifelong medication. Significantly, given a choice between cutting sugar and starchy carbs OR starting drugs no patient has chosen medication. Cumulatively, our annual diabetes drug budget expenditure is now £61 000 less than is average for the 17 GP practices in our area. By November 2021 we had 109 cases of drug-free T2D remission.’ Unwin and colleagues have recorded significant improvements in liver function, lipid profiles, renal function - see, for example, Unwin et al (2021) - and blood pressure.
Finally
The burgeoning evidence base confirming insulin resistance's role in many long-term conditions and how it can be improved confirms that primary care health professionals can change lives for the better. As Dr David Unwin says … ‘Such cheerful medicine!’.