What You’ll Learn: 

• Obesity is the number one factor associated with insulin resistance and metabolic dysfunction due to the impact of free fatty acids and inflammation on your cellular health.
• Other factors that may contribute to insulin resistance include poor diet and the health of your gut microbiome.
• Although insulin resistance can go undetected, there are a few physical signs to watch out for, including skin tags and darkened skin under your armpits and around your neck.
• The best way to test for insulin resistance is the HOMA-IR test, but checking your hemoglobin A1c (HbA1c) levels is also a practical way to stay on top of your blood sugar.  
• A low-carb or ketogenic diet is the optimal diet for insulin resistance as it removes excess glucose and helps to resensitize your cells to insulin's signals. 
• Other lifestyle tips for improving insulin resistance include physical activity, stress management, and prioritizing sleep.

Although you may be aware of what insulin resistance refers to, understanding the roots of insulin resistance and how this condition develops can help you make dietary and lifestyle decisions that will support long-term metabolic health. 

As insulin resistance progresses, it can turn into prediabetes and, ultimately, diabetes if it's not managed. The good news, however, is that you can do plenty of things to keep your body's sensitivity to insulin in a healthy range, and even turn things around if you're already experiencing insulin resistance. 

In this guide, we'll walk you through:

• The importance of insulin in metabolic health and what happens when your body becomes resistant to this hormone
• How insulin resistance develops
• The different signs to watch out for to detect insulin resistance, along with tests that your doctor can order
• The best dietary approach for managing insulin resistance and promoting insulin sensitivity
• Research-backed lifestyle tips for helping your body become more sensitive to insulin signaling 

Introduction to Insulin Resistance and Prediabetes

According to the American Diabetes Association (ADA), the incidence of insulin resistance is steadily climbing worldwide. A 2020 study showed that between 15.5 to 46.5% of adults currently deal with some level of insulin resistance[1].

In an even more recent study, researchers found that four in ten young American adults have insulin resistance – that's a staggering 40% of the population[2].

Although you can experience insulin resistance without developing diabetes, it's a precursor that must be managed to prevent future complications. 

Before we jump into the potential causes of insulin resistance, let's first briefly review what insulin is and how this hormone works in your body. 

Insulin is a hormone released by your pancreas, specifically via cells known as pancreatic islet cells, to help shuttle nutrients out of your blood and into your cells. The primary trigger for insulin release is the presence of glucose in your blood, although both free fatty acids and amino acids can also influence glucose-induced insulin secretion[3]. Furthermore, some amino acids (from protein), can directly stimulate increases in insulin, but on a much more subtle level than glucose[4]. 

Generally speaking, insulin's primary job is to help keep your blood glucose levels stable by moving excess glucose out of your bloodstream and into your cells where it can be used as immediate fuel, or stored for later. 

Healthy cells are highly sensitive to insulin signals, allowing them to "open their doors" to allow glucose in when insulin comes knocking. In the case of insulin resistance, however, your cell's sensitivity is diminished, creating insulin-resistant cells that aren't able to respond to insulin signals. As a result, both glucose and insulin build up in your blood without anywhere to go. 

As your pancreas continually tries to keep up with the glucose demand, it can become damaged and eventually unable to produce enough insulin. As a result, blood sugar becomes chronically high, leading to prediabetes and diabetes.

Understanding the Causes of Insulin Resistance

So, what exactly causes insulin resistance in the first place? We don't have one clear answer at this point, but several risk factors seem to play a role. Chief among them is obesity.

More specifically, excess fat tissue is understood to instigate insulin resistance via two potential pathways; free fatty acids and inflammation. 

Free fatty acids (FFA)

Most people that would be considered obese have elevated levels of free fatty acids in their blood. FFAs are known to cause insulin resistance in both liver cells and peripheral (muscle) tissue by inhibiting glucose uptake and storage at these sites. FFAs also inhibit the suppression of glycogenolysis in your liver, which is an insulin-mediated process of breaking down glucose. By inhibiting insulin suppression of this activity, glucose is released from liver cells at inappropriate times, further contributing to high blood sugar and therefore inhibiting glucose uptake by liver cells[5]. 

Inflammation

In most cases, obesity is accompanied by inflammation in your body, which may contribute to metabolic dysfunction. Studies show that FFAs released from fat cells activate inflammatory pathways in various tissues throughout the body, including adipose tissue, skeletal muscle, liver, gut, brain, and specifically, pancreatic islet cells (responsible for insulin release). These inflammatory processes directly impact the function of these cells and tissues leading to issues like metabolic dysfunction and insulin resistance[6].  

The trouble with obesity as a causative factor for insulin resistance is that many people with metabolic issues have a hard time losing weight, and may gain weight much more readily than people with a healthy metabolism. This creates a spiral of weight gain, coupled with insulin resistance, which drives further weight gain, and the cycle continues. 

Therefore, getting to the root of the issue has to come down to your diet, which we'll discuss in detail later in the guide.

Other Potential Causes Of Insulin Resistance

Gut Dysbiosis

The microbiome is getting more and more attention these days as we are continuously learning how impacting our gut bugs are in the maintenance and activity of every system in our body. Unsurprisingly, studies show that irregularities in gut bacteria can directly impact metabolic health in various ways, including[7]:

• Satiety signaling
• Insulin resistance 
• Obesity
• Epigenetic factors that influence metabolism 
• The metabolism of bile acids and subsequent changes in metabolic signaling

High Fructose Consumption

Excessive consumption of fructose coming from added sugars (not fruit) is highly linked to insulin resistance, particularly in the liver. Although it's likely a combination of factors that lead to insulin resistance and prediabetes, watching your intake of sugar-sweetened beverages and high-fructose corn syrup is a good idea[8]. 

Insulin Resistance: What to Look For

While you may not be able to identify insulin resistance by how you feel, there are several signs you can watch for that may indicate your body has become resistant to insulin signaling. 

These include[9]: 

• Waistline over 40 inches in men and 35 inches in women
• The appearance of skin tags in the armpit, on the back, or on the neck
• The development of darkened skin, a condition called acanthosis nigricans, in the armpit, back, or neck

Otherwise, you'll want to look at blood tests that can give you an idea of your metabolic health. If any of the below markers show up, it's an indication that you may have insulin resistance[10]: 

• A blood pressure reading of 130 over 80 or higher
• A fasting blood glucose level equal to or above 100 milligrams per deciliter 
• A blood sugar level equal to or above 140 milligrams per deciliter two hours after a glucose load test
• An A1C between 5.7% and 6.3%
• A fasting triglycerides level over 150 milligrams per deciliter
• And an HDL cholesterol level under 40 milligrams per deciliter in men, and under 50 milligrams per deciliter in women.

How To Test For Insulin Resistance 

If you want to test for insulin resistance directly, there is a test you can ask for from your healthcare provider called HOMA-IR (Homeostatic Model Assessment of Insulin Resistance).

HOMA-IR gives you insight into whether your insulin levels are within a normal range or if your pancreas is on overdrive. This test is actually an indirect measure of insulin resistance, calculated from your fasting glucose and fasting insulin levels. 

With this information, your HOMA-IR results can tell you how much insulin your body needs to make in order to control your blood sugar levels. 

While HOMA-IR is the gold standard for measuring insulin resistance, there are other tests that can be used as a proxy for IR. One test that can be especially helpful for determining how well your body is managing blood sugar is the Hemoglobin A1C test (HbA1c). This test looks at your average blood sugar over the past three months, and is one of the most common tests used for diagnosing prediabetes and diabetes. 

The HbA1c test is also a great ally to have as you work on re-sensitizing your body to insulin. With this test you can track your progress and see how your body is changing by assessing your blood sugar levels not just in the moment, but as your body changes its metabolism. Unlike the HOMA-IR, you can test your HbA1c at any time in the comfort of your own home, making it much more accessible as well. 

Another way to help measure insulin resistance is looking at your insulin sensitivity which can be done with a glucose tolerance test. You could also use your Triglyceride:HDL ratio as a proxy for insulin sensitivity if you have this data on hand.

Insulin Resistance Diet: Foods to Eat and Foods to Avoid

When your cells aren't responding properly to insulin and glucose is building up in your blood, the number one thing you'll want to do is manage your influx of carbohydrates. For obvious reasons, the fewer carbohydrates you consume, the less your body has to rely on insulin. 

However, reducing your carbohydrate load doesn't just eliminate the immediate issue of blood sugar; studies also show that when people follow a low-carb diet, it can help to resensitize their cells to insulin[11]. 

Low-carb dieting can also help you shed stubborn pounds that are driving your insulin resistance in the first place, making this dietary approach ideal for anyone that's struggling with blood sugar control[12][13].

Foods To Avoid

When following a low-carb diet, you'll want to keep an eye on the number of carb-heavy foods you consume. While you don't necessarily have to consume zero carbohydrates, you'll want to save your carb allotment for nutrient-rich foods like low-carb vegetables and berries (in moderation). At the same time, to make the most of your diet, you'll want to make sure that you're focusing on anti-inflammatory foods, and avoiding foods that are known to increase oxidative stress and inflammation in your body. 

To accomplish this, steer clear of foods like:

• Processed grain products (bread, pasta, pizza, crackers, muffins, etc.)
• Whole grains (rice, wheat, oatmeal, millet, quinoa, etc.)
• Honey and maple syrup
• Most fruit (with the exception of berries, avocado, lemon, and lime)
• Packaged foods (frozen meals, snacks, etc.)
• Desserts (ice cream, cookies, brownies, cake, etc.)
• Starchy vegetables (sweet potato, potato, yams, corn, beets, squash)
• Seed oils that drive inflammation (canola oil, peanut oil, soybean oil, etc.)

Focus To On

• Low-carb vegetables (broccoli, cauliflower, asparagus, bok choy, celery, peppers, cabbage, etc.)
• High-quality meat (organic and grass-fed beef, organic poultry, bison, venison, etc.)
• Organic eggs and dairy
• Fish (especially fatty fish like salmon, mackerel, and sardines which are rich in omega-3 fats. Omega-3s which help to calm inflammation and may reduce insulin resistance) 
• Nuts and seeds
• Healthy sources of fat like organic butter, ghee, olive oil, avocado oil, and coconut oil

Try Intermittent Fasting 

Intermittent fasting (IF) is another dietary approach that's shown promise in helping to improve insulin resistance[14]. Giving your body a break from food allows it to reset and clear away old debris, giving your detox pathways a chance to take over while your digestion is resting.  

There are several different fasting protocols out there, which makes IF a flexible option for most people. Some of the most popular include:

• A 24-hour fast: (ex/ fasting from 12 PM on Monday to 12 PM on Tuesday). This protocol is usually only followed once a week, maybe twice if you have a lot of weight to lose.
• 16-hour or 14-hour fast: (ex/ finish dinner by 6:30 AM and have breakfast around 10:30 AM). This protocol can be used every day.
• 5:2 diet: this protocol involves eating your typical diet for 5 days per week, and then restricting your calories to around 500 per day for two days each week. 

Managing Insulin Resistance: Tips and Tricks

In addition to changing your diet, there are several lifestyle changes to be aware of that can help to resensitize your cells to insulin. Below are some of the most practical research-backed tips for managing insulin resistance and regulating blood sugar.

Physical Activity

Physical activity is one of the most well-researched methods for enhancing glucose clearance from your blood and promoting insulin sensitivity and reverse insulin resistance. 

When you exercise, your cells become hungry for fuel as you burn through your energy reserves. This sets off a cascade of pathways that help usher glucose into your cells. Specifically, proteins called "glucose transporters" are translocated to the cell membrane creating more "doors" for glucose to enter. This is your body's way of supplying you with more energy when you need it most.  

Now, here's where things get interesting. Although some of these glucose transporters function independently of insulin, studies show that after your workout the increase in glucose transporters is replaced by improved cellular sensitivity to insulin. In other words, once your cells start to receive more glucose independently of insulin, they naturally start waking up to insulin signals[15][16].

Physical activity can take any form; the key is that you stay active on a regular basis. This could mean taking a nice long walk every evening, doing some weight training at the gym, going to a workout class with friends, joining a team sport, or taking up tennis or swimming. At the end of the day, the key is to find something you enjoy so you'll stick with it and have fun while doing it. 

When your physical activity doubles as a way to de-stress, you'll be killing two birds with one stone (more on stress and insulin to come).

Weight Loss 

As mentioned earlier, insulin resistance is closely associated body weight, with obesity putting you at a higher risk of insulin resistance. In fact, research has shown that more than 70% of the obese population has issues with insulin sensitivity[17]. 

Due to the impact that excess fat tissue, especially belly fat (visceral fat) has on inflammation and the production of free fatty acids (FFA), when you lose weight, you'll naturally be minimizing these two factors. 

One study looked at the impact of long-term weight loss on individuals with insulin sensitivity and found that those who kept the weight maintained improved insulin sensitivity so long as their weight remained stable. However, those that re-gained weight returned to an insulin-resistant state, showing just how impactful excess fat tissue can be on your body's insulin response[18]. 

Of course, when metabolic issues come into play, suggesting weight loss can be a lot easier said than done. That said, if you can make the appropriate dietary shifts and increase your physical activity, your body's tendency to store fat will shift – especially if you're not overloading it with glucose.

Quit Smoking 

If you're a smoker, you can add the risk of insulin resistance to your list of reasons to quit. Studies show that the connection between heart disease and cigarette smoking may come down to the impact of smoking on insulin resistance[19]. 

According to the CDC, the nicotine in cigarettes can change your cells in a way that doesn't allow them to respond to insulin. Furthermore, the other chemicals found in cigarettes promote inflammation in your body, which can further aggravate insulin resistance[20]. 

Prioritize Sleep

When it comes to weight loss and metabolic health, prioritizing sleep is vital. Studies show that several different mechanisms connect poor sleep with weight gain and insulin resistance, including increased hunger hormones, impaired glucose tolerance, and reward-driven brain activity[21].

Your body is meant to sleep during specific hours of the day according to your natural circadian rhythm. This rhythm, also known as your internal clock, is managed by your hormonal system, which tells your body when to sleep, eat, wake, and so on. Disruptions to your sleep cycle can impact your circadian rhythm and cause downstream disturbances in your hormones, including insulin. As a result, many people find that when they experience poor sleep it directly impacts blood sugar (among many other hormonally driven processes)[22]. 

If you're someone that has a hard time sleeping at night there are likely a variety of factors influencing your circadian rhythm. Although it may take some time to get your sleep schedule on track, below are some suggestions that will enhance your body's production of melatonin (the sleep hormone), and help you wind down at night to promote more restful sleep.

Avoid Blue Light

Blue light is emitted from your home lighting system, lamps, and electronic devices. When this artificial light hits your retina, it tells your brain that it's still daytime and inhibits melatonin production. To avoid blue light at night, try the following:

• Turning off electronics a couple of hours before bed
• Read by candlelight instead of watching TV
• Invest in blue light-blocking glasses to wear in the evening
• Turn your lights down low in the evening, so they aren't as bright
• Turn off your WiFi at night (WiFi signals also impede melatonin production)

Wind Down

With many people working from home these days, our work life tends to blend into home life pretty seamlessly. Unfortunately, this can make it much harder to wind down in the evening. If you have a hard time shutting off at night, try the following:

• Putting your phone on airplane mode
• Use a journal to keep track of what you need to do and any thoughts or feelings you're dealing with that you haven't processed from your day. Many people go to bed still spinning on the day's events and activities, which makes it challenging to let go and drift off to sleep.
• Drink calming herbal teas like chamomile or lemon balm before bed. These teas have a calming effect on your nervous system and can help you shift into sleep mode.
• Try gentle yoga or deep breathing in the evening to stimulate your parasympathetic nervous system. 

Stress Management

Along with excess body fat, a stressful lifestyle is another well-known contributing factor to insulin resistance and diabetes. 

When you're under stress, your body enters "fight or flight" mode, also known as sympathetic activation. Research shows that in sympathetic mode, your body's insulin sensitivity becomes impaired, and when stress is chronic, it can eventually lead to insulin resistance[23]. 

In addition to improving your sleep and incorporating some of the "wind down" techniques mentioned above, research shows that engaging in mindfulness meditation is an excellent way to improve your resilience to stress. By learning to look at your life objectively, your stressors become less all-encompassing, allowing you to find more spaciousness in your mind for alternative ways of thinking and being[24].

Exercise is another fantastic way to calm your body's stress response. Physiologically when you engage in movement, it helps to shift your body's state, enhancing the release of feel-good hormones (endorphins) and can help you burn off some energy, leaving you feeling lighter and more clear-headed[25]. 

Conclusion: Taking Control of Insulin Resistance and Prediabetes

A diagnosis of insulin resistance or prediabetes does not mean you're destined to develop diabetes or other metabolic complications like high blood pressure and cardiovascular disease . In fact, you can see these diagnoses as signals from your body that it wants you to make some changes so you can live a long and healthy life.

Taking charge of your diet is the number one thing you can do to turn around insulin resistance and ensure that you're giving your body what it needs for optimal metabolic health. A diet low in carbohydrates and rich in nutrient-dense foods can alter your cells' sensitivity to insulin while also helping to reduce other risk factors for diabetes.

That said, nothing in your body happens in a vacuum, which means that if you want to turn things around, you'll also need to take inventory of other lifestyle factors. This means prioritizing sleep, developing healthy stress management practices, and getting in regular physical activity. 

The good news is that once you get the ball rolling in one of these areas, the others become much easier to manage. 

References 

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2. Parcha, Vibhu, et al. "Insulin resistance and cardiometabolic risk profile among nondiabetic American young adults: insights from NHANES." The Journal of Clinical Endocrinology & Metabolism 107.1 (2022): e25-e37.

3. Fu, Zhuo, Elizabeth R Gilbert, and Dongmin Liu. "Regulation of insulin synthesis and secretion and pancreatic Beta-cell dysfunction in diabetes." Current diabetes reviews 9.1 (2013): 25-53.

4. Newsholme, P., et al. "Amino acid metabolism, insulin secretion and diabetes." Biochemical Society Transactions 35.5 (2007): 1180-1186.

5. Boden, G. "Effects of free fatty acids (FFA) on glucose metabolism: significance for insulin resistance and type 2 diabetes." Experimental and clinical endocrinology & diabetes 111.03 (2003): 121-124.

6. Wu, Huaizhu, and Christie M. Ballantyne. "Metabolic inflammation and insulin resistance in obesity." Circulation research 126.11 (2020): 1549-1564.

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9. https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance#symptoms

10. https://www.mayoclinic.org/diseases-conditions/obesity/multimedia/vid-20536756

11. Foley, Peter J. "Effect of low carbohydrate diets on insulin resistance and the metabolic syndrome." Current Opinion in Endocrinology, Diabetes, and Obesity 28.5 (2021): 463.

12. Silverii, Giovanni Antonio, et al. "Effectiveness of low‐carbohydrate diets for long‐term weight loss in obese individuals: A meta‐analysis of randomized controlled trials." Diabetes, Obesity and Metabolism 24.8 (2022): 1458-1468.

13. Wheatley, Sean D., et al. "Low carbohydrate dietary approaches for people with type 2 diabetes—a narrative review." Frontiers in Nutrition 8 (2021): 687658.

14. Yuan, Xiaojie, et al. "Effect of intermittent fasting diet on glucose and lipid metabolism and insulin resistance in patients with impaired glucose and lipid metabolism: A Systematic Review and Meta-Analysis." International journal of endocrinology 2022 (2022).

15. Holloszy, John O. "Exercise-induced increase in muscle insulin sensitivity." Journal of applied physiology (2005).

16. Kirwan, John P., et al. "Effects of 7 days of exercise training on insulin sensitivity and responsiveness in type 2 diabetes mellitus." American Journal of Physiology-Endocrinology and Metabolism (2009).

17. Xu, Jie, et al. "Obesity-stroke paradox exists in insulin-resistant patients but not insulin sensitive patients." Stroke 50.6 (2019): 1423-1429.

18. Clamp, L. D., et al. "Enhanced insulin sensitivity in successful, long-term weight loss maintainers compared with matched controls with no weight loss history." Nutrition & diabetes 7.6 (2017): e282-e282.

19. Mouhamed, D. Haj, et al. "Effect of cigarette smoking on insulin resistance risk." Annales de Cardiologie et d'Angéiologie. Vol. 65. No. 1. Elsevier Masson, 2016.

20. https://www.cdc.gov/diabetes/library/features/smoking-and-diabetes.html

21. Reutrakul, Sirimon, and Eve Van Cauter. "Sleep influences on obesity, insulin resistance, and risk of type 2 diabetes." Metabolism 84 (2018): 56-66.

22. Stenvers, Dirk Jan, et al. "Circadian clocks and insulin resistance." Nature Reviews Endocrinology 15.2 (2019): 75-89.

23. Yaribeygi, Habib, et al. "Molecular mechanisms linking stress and insulin resistance." EXCLI journal 21 (2022): 317.

24. https://www.apa.org/topics/mindfulness/meditation

25. https://www.mayoclinic.org/healthy-lifestyle/stress-management/in-depth/exercise-and-stress/art-20044469