Insulin Resistance: Signs, Causes and How to Improve Your Metabolic Health
Could insulin resistance be affecting your health without you realising it? This guide explains the early signs of insulin resistance, its connection with weight gain, fatigue, blood sugar and metabolic health, and how sleep, nutrition, exercise and stress management can help improve insulin sensitivity and support long-term health.
Insulin resistance as a condition seems to be spoken about everywhere now, if you are looking for it. But if you are not, then there is a great number of people who are still unaware of it. For every 30 patients I see in my clinics for high cholesterol, or hypertension, or kidney disease there seems to be about one who has heard of insulin resistance, but they are still not sure what it means for their personal health.
Insulin resistance is linked to the development of more than 30 diseases and health conditions, including PCOS, hypertension, atherosclerosis, heart disease, fatty liver disease, gout, arthritis, dementia, Alzheimer’s, depression and other. Thus, it is important to understand what insulin resistance is as a metabolic condition, detect at its early stages and create healthy habits to prevent its worsening effects, or reverse it before it starts creating serious health problems.
The biggest misconception about insulin resistance is that it should show as raised blood sugar levels. This is not necessarily the case. Insulin resistance is a condition of metabolic dysfunction, which arises months and years before its well-known consequence - type 2 diabetes (T2D) - is diagnosed. Research shows that insulin resistance precedes the development of T2D by about 10-15 years. (Reference 1).
Insulin resistance is an impaired ability of the body to uptake glucose into the cells to utilise for energy - these are the cells of the muscle, fat tissue (adipose tissue) and the liver. When food is digested, and blood sugar - glucose - is released into the bloodstream it cannot be taken into the cells by itself, it needs an accompanying ‘agent’ - the hormone insulin, which is released by the pancreas. Insulin is a necessary companion for glucose, without it glucose is not taken up into the cells. But the problem is that although insulin is needed by the body, we don’t need much of it. It is a natural response of the body to produce insulin, which is needed for life, however, due to our modern lifestyle a large number of people produce an insulin response too much and too often during the day, constantly cycling up and down of the glucose-insulin levels, something that biology did not design us to do.
Some metabolic health researchers call the insulin response “too much of a good thing” (Reference 3). Insulin is an anabolic hormone, which means that it facilitates growth, and it is for this reason that presence of high levels of insulin favours energy storage over energy usage. When the cells in the human body are continuously exposed to elevated insulin levels, they temporarily reduce their response to insulin to protect themselves from an overload of sugar or hormone signalling. In studies on mice, a modest lowering of circulating insulin causes inability to gain weight despite being fed a high-fat diet.
Insulin resistance origins
The ‘evolutionary mismatch’ theory of the development of insulin resistance informs us that most likely insulin resistance has evolved as our evolutionary adaptation to periodic starvation. (Reference 4)
Our hunter-gatherer ancestors of the pre-agricultural revolution of 10,000 years ago ate the diets richly diverse in plants and tubers. These high amounts of fibres (it is believed that our ancestors ate up to 125 fibre types per week) gave rise to a more diverse gut bacteria composition than that seen in the current Western dietary patterns.
The hunter-gatherers foraged on the foods they found in their environment - these were plants, flowers, roots of plants, vegetables, bark of trees. They were complex carbohydrates that required hours of processing by the gut. For protein sources, they hunted for large mammals (deer, elk), small mammals (rabbits, beavers), fish and shellfish, as well as insects, amphibians, reptiles and birds.
Fruit were seasonal, berries had even less timely season, and very rarely they found honey. These were the only sources of foods that could be metabolised into quick sugars. Predominantly, our ancestors’ diet was rich in complex carbohydrates that took a really long time to get metabolised by the gut. One of the hypothesis for lowered glucose sensitivity and development of insulin resistance in modern times is that the foods that elicited insulin response and thus promoted fat storage helped survival in primitive life, which was characterised by periods of "feast and famine”; but our modern day urban lifestyle and Western diets have turned detrimental for health and longevity.
Symptoms of insulin resistance
Insulin resistance often presents with quite subtle symptoms that are hard to pinpoint to this specific condition, and therefore it may go undetected for years.
Most frequent signs of insulin resistance are feeling sleepy, lethargic after a carbohydrate-rich meal (such as a bowl of pasta, or a rice-based meal), craving sugary foods and snacks daily, sometimes several times per day, increased weight, especially around the abdomen, nighttime sweats.
When insulin signalling becomes impaired, which happens when the cells that previously took up glucose and insulin begin to ‘shut their gates’, more glucose starts circulating in the bloodstream. When blood sugar levels have been regularly high for quite some time, they are detected by the HbA1c test (glycated hemoglobin), which checks glucose levels for the previous two to three months. Alternatively, measuring fasting insulin is a good standard for understanding if you have insulin resistance or not. Some private labs offer a HOMA-IR - Homeostatic Model for Insulin Resistance - a blood test that uses a mathematical model based on your fasting glucose and fasting insulin levels.
If the person continues having the same diet and lifestyle, insulin resistance often leads to the development on prediabetes and type 2 diabetes.
Insulin resistance is hard to pinpoint and identify even for a medical professional. The symptoms of fatigue or constant sugar cravings are not definitive enough in themselves. The standard HbA1c test offered at GP clinics only detects an abnormally high levels, when HbA gets above 42mmol/mol, which is then diagnosed as prediabetes. However, by this point there has been a metabolic dysfunction present for quite some time, and the body can compensate for reduced insulin sensitivity for an extended period of time. Some researchers claim the HbA of 37 - 38mmol/mol and above is a good detection point of impaired glucose tolerance and thus serving as a signal of insulin resistance. (Reference 7). I have written about how to spot unbalanced blood sugar levels in a variety of signs the body gives you.
One of the telltale signs of insulin resistance is weight gain that is predominantly concentrated around the belly. This is particularly relevant around midlife. Many 40+ year olds are left perplexed by this new phenomenon - why is weight starting to accumulate around the belly and why is it so difficult to get rid of it? There are several factors at play for accumulation of belly fat. Sleep quality and quantity, hormonal changes, presence of chronic stress and, of course, diet all play a cumulative role.
For women, in particular, being 40+ means that they are moving closer to menopause, where diminishing levels of the hormone estrogen create lower insulin sensitivity and can lead to the development of insulin resistance. Research increasingly shows that the menopause transition is associated with changes in body composition and a higher cardiometabolic risk, including increased insulin resistance and greater accumulation of abdominal, or visceral fat. Visceral fat is the fat that accumulates around the mid-section as well as wraps around inner organs. There are people who can have a lean-looking body, however, with visceral fat accumulated internally.
What can improve insulin sensitivity
Diet plays a significant role in the development and outcome of insulin resistance, however, as it is a metabolic dysfunction, there are other less known factors that play essential roles. Sleep is one of those factors.
Sleep
Lack of sleep has long been linked to the disruption in metabolic hormones’ production, the hormones responsible for hunger and satiety - ghrelin and leptin, respectively, resulting in higher energy intake, high insulin resistance and risk for diabetes type 2. (Reference 8)
One study found that age-related sleep quality deterioration is associated with the development of sarcopenia - loss of muscle mass, and a potential promotion of insulin resistance state. The study demonstrated that just one night of sleep loss acts as a catabolic mechanism, promoting loss of muscle mass and function. (Reference 9) I have written on the role of sleep and its interplay with our metabolism here.
Sleep has a greater significance for metabolism in midlife. Studies conducted on women of menopausal age show the connection between insufficient or disrupted sleep with development of insulin resistance, poor appetite regulation and increased food intake.
Sleep has indeed a multitude of effects on metabolism. First, is the circadian aspect of sleep: our sleep and wake cycles are biologically designed to make us physically and mentally active from the hours of 6 - 7:00 am till about 8 pm. This is orchestrated by the sleep and wake cycle of the SCN (suprachiasmatic nucleus located in the hypothalamus). The average adult produces the levels of cortisol and melatonin - the hormones of energy and sleep respectively at similar times of the day on a 24-hour+ cycle. In people with dysregulated circadian clocks - such as going to bed after midnight, having a working activity spell at 9 or 10 pm, having later meals - these circadian (dysregulated) aspects make a detrimental impact on the way the body handles glucose and insulin, with resulting impaired glucose sensitivity and higher insulin resistance.
Several studies done by Eve Van Cauter, PhD, who studies the role of sleep on metabolism at the University of Chicago, have found that two nights of sleep deprivation (4 hours) showed a 24 percent increase in appetite, with a strong craving towards sweets, cookies, salty high-energy snacks, as well as bread and pasta. By restricting the participants’ sleep Professor Van Cauter found that the levels of ghrelin - the hunger hormone - were elevated by 28 percent; while the levels of leptin - the hormone of satiety - decreased by 18 percent. This is a double whammy effect for human metabolism. Ghrelin is secreted by the stomach to signal to the person’s hunger levels; leptin is produced by fat cells to signal to the brain that enough food has been consumed, time to stop. Van Cauter’s studies demonstrate that when sleep is cut short, those signalling are both off.
In my own interviews with patients and clients I often hear the phrase “I just cannot stop eating.” It is precisely due to the effects of lowered leptin activity that satiety cues are disrupted with poor sleep quality.
Exercise
What is the best exercise protocol to forestall insulin resistance and reverse it?
Research predominantly concentrates on the effectiveness of the two high intensity exercise protocols: the Norwegian 4-4 and the 10 x 1-minute (also called “the Little Method”). Instead of singling out a specific sport, researchers concentrate on the importance of work-to-rest ratios and the target heart rate, which High Intensity Interval Training (HIIT type) workouts are best designed around.
The 4-4 Norwegian protocol consists of 4 minutes’ work intervals, where the individual aims to reach 85-90% of their maximum heart rate. The workout consists of 4 intervals of 4 minutes’ activity, each followed by a 3-minute rest.
The 10x 1-minute is a training protocol where 1-maximum activity work is followed by 1-minute rest, aiming to achieve 90% of one’s maximum heart rate. A recent study (Reference 11) showed that just 6 sessions of the 10x -1 training regime within the 2-weeks’ period significantly improved hyperglycaemia and “cleared glucose pathways” in the study group with diabetes 2 and obesity.
These HIIT-type workouts do not identify which sport is best, cycling or running, - the maximum benefit is from the type of exercise that engages large skeletal muscle groups - both cycling and running are great examples of these.
There are currently many brand names made around the HIIT protocol. These are classes in the gym, in parks and also boutique-style gyms centred on the principles of HIIT. To do HIIT properly, with the work-to-rest ratio that has been tested to create metabolic benefits mentioned above, one needs to be careful at choosing those classes and settings. A HIIT workout cannot last 45 or 50 minutes, which is the structure of most classes. This means, that at most times, participants stay in their moderate rate of exertion, often wondering why they are not seeing results from doing 3 or 4 HIIT classes per week. If this is something you have been wondering about too, look at quality rather than quantity.
What about people who cannot tolerate long bouts of activity, or those with restricted time availability? A reduced-exertion HIIT (REHIT) is a relatively new studied protocol to follow. Published trials show that doing just one or two 10 to 20 seconds ‘all-out’ bicycle sprints within a 10-minute session can successfully improve one’s insulin sensitivity (the study was conducted on a 6-week period). (Reference 12)
In my practice with over 1,500 patients I have seen at my NHS clinics to-date, one peculiarity has emerged: I find when people exercise, they are not aware of how they need to exercise.
Movement is absolutely key, any form of movement is beneficial for the body, but the crucial difference between a leisurely walk and a walk on the treadmill as a workout is in the heart rate. For exercise to produce positive changes to your metabolism, you need to be sweating and out of breath for an extended period of time. How much time depends on your fitness levels and on your exercise and metabolism goals. This is easier to achieve than most people think: you don’t have to have a heart rate monitor - you can simply go by the changes you notice during your exercise session: Are you breaking into sweat? Are your cheeks reddened? Do you find it difficult to breathe? Are you out of breath? If your answer is “no” to most of these, your exercise is not affecting your metabolism. In order for the body to start utilising fat storage, you need to create your exercise routine where 2-3 times a week you have prolonged periods of giving yourself a 7 or 8 out of 10 on the PRE scale (perceived rate of exertion). I have written about creating exercise routines for health benefits here.
Stress
Stress is one of the major drivers of metabolic dysfunction. There are several mechanisms by which stress can promote development of insulin resistance.
As the human body is constantly looking to achieve homeostasis, or balance, in periods of stress most people resort to eating in order to comfort themselves. A smaller proportion of people cannot eat in stress.
The choices of foods for stress comfort are high-sugar, high-fat foods - called highly-palatable foods, they are found to temporarily reduce stress. (Reference 13) Consuming sugar and fat triggers a rapid release of dopamine, activating the reward pathways that block the brain cells linked to anxiety. However, over time, as the brain associates the taste of comfort foods with a quick drop in emotional distress and anxiety, it creates a learned habit of sugar cravings to ‘self-medicate’ itself in future stressful events.
High-sugar, high-fat foods are high-calorie density foods, which promote weight accumulation.
On the physiological level, stress is the activation of the HPA axis (hypothalamus-pituitary-adrenal axis). HPA activation means the levels of the hormone cortisol are raised. Cortisol stimulates gluconeogenesis - glucose production in the liver, as the liver gets the signal to make energy available immediately. A stress response is an evolutionary mechanism that served us to run away into safety when being pursued by a predator. In order to have energy for running into safety, glucose is made available in the bloodstream with insulin receptors being temporarily deactivated, so that glucose stays for longer in the bloodstream.
Repeated activation of the HPA axis produces regularly raises blood sugar levels and promotes visceral fat accumulation, which drives insulin resistance. (Reference 14)
Helping your body mitigate stress should not be a reactive strategy but a proactive one. The daily stressors would never go away, stress is an indispensable component of our modern life, thus learn de-stressing practices and incorporate them into your daily routine.
Meditation, journaling, deep breathing, yoga, stretching, listening to calm or classical music, walks in nature, massage, painting, drawing, engaging in your favourite hobby - this is not an exhaustive list of activities where our brain relaxes and has a chance to recover from stress. Treat these as your daily non-negotiables by creating your own list of 2-3 activities that you engage in every day. Once your body learns to switch from a high-stress state to a relaxation state, you will find the effects of stress not impactful on your health.
When to seek medical help
Have you noticed that your sleep is disrupted, and no matter what you do, your sleep quality and quality is low?
Do you have low energy levels regularly, unable to rest and recover during the week?
Do you have visceral fat that has remained steady for more than a year?
Have you got a recent diagnosis of raised blood pressure?
These are signs of insulin resistance, which left unattended could result in prediabetes or type 2 diabetes diagnosis if left unaddressed. Speak to your doctor, do the HbA1c test or fasting insulin, and engage in the strategies I have mentioned above to help your body regulate blood sugar levels bringing them back to healthy.
At Boost My Energy, I help clients create healthy strategies in their diet, sleep, stress and exercise to optimise their metabolism, reverse insulin resistance and prevent metabolic syndrome conditions - hypertension, fatty liver disease, heart disease, kidney disease, diabetes 2. Here are metabolism-centred programmes that have helped many people regain their metabolic health to remain active with great energy levels daily.
Unhealthy food and psychological stress: the association between ultra-processed food consumption and perceived stress in working-class young adults: https://pmc.ncbi.nlm.nih.gov/articles/PMC8103503/