Insulin Resistance: 4 Causes That Aren’t Related to Food
Written by: Rebekah B.
Reviewed by: Emily J., MSc RD
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Diet isn’t the only thing that contributes to insulin resistance — exercise, stress and inflammation, gut bacteria, and sleep play an important role as well.
You may have heard of insulin resistance, a condition that affects nearly 40% of non-diabetic adults between the ages of 18 and 44 years old. Researchers have linked it to a number of conditions, including obesity, type 2 diabetes (which affects 95% of people with diabetes), cardiovascular disease, metabolic syndrome, and more — but its symptoms aren’t always obvious. So what is insulin resistance, and what causes it to develop? What are some early warning signs, and what changes can you make to your lifestyle to avoid it?
Insulin is a hormone produced by the pancreas that helps control the amount of sugar (glucose) in your blood. As glucose enters cells in your muscles, fat, and liver, it turns into energy that helps your body function properly. But when your cells don’t respond correctly to insulin, your body is unable to convert glucose from your blood into energy. In an attempt to balance the glucose levels, your pancreas starts to release more insulin. This excess amount of insulin can cause your cells to become desensitized and ultimately stop responding to it which can cause your blood glucose levels to rise to unhealthy levels. As the glucose levels continue to rise, this can tax the pancreas and lead to Type 2 diabetes.
The body’s inability to respond to insulin (and use the sugar in your blood for energy) is known as insulin resistance. Because it’s so closely tied to glucose and the foods we eat, that’s where we usually start. But it’s not the only factor — there are several other key causes of insulin resistance as well, including an inactive lifestyle, chronic stress and inflammation, lack of proper gut microbiota, and consistently getting poor sleep. (Genetics, health conditions such as PCOS, Cushing’s syndrome, and a family history of diabetes can also put you at risk.)
Insulin resistance tends to go hand in hand with high blood glucose levels, which, if left unchecked, are associated with symptoms such as increased hunger and thirst, blurred vision, headaches, and frequent urination. That said, not everyone who has insulin resistance experiences noticeable side effects — which means it often goes undetected until a blood test that specifically measures glucose levels reveals high fasting blood glucose (blood glucose that is elevated after a period of not eating for 8-10 hours) or high blood glucose 2 hours after a meal (typically >140mg/dL).
Regular exercise has a slew of health benefits: it can help you lose weight, build muscle, improve heart health, and much more. On the other hand, lack of exercise can actually reduce your insulin sensitivity — which increases your chance of developing insulin resistance. In one study, scientists divided 53 Type 2 diabetic women into two groups (exercise and control). The exercise group completed warm-up stretches and flexibility exercises for 10 minutes, followed by walking for half an hour, and then stretching for 10 minutes in the seated position. They completed this exercise regimen three times a week for eight weeks in a row. The exercise led to differences in waist and hip circumference, BMI, plasma insulin, and insulin resistance. Researchers observed significant differences between the two groups at the end of the study, with exercise proving effective in lowering plasma glucose, insulin levels, and insulin resistance. Other studies indicate that completing two to three sessions of resistance training for 8 to 26 weeks can enhance insulin sensitivity by up to 48%.
To reduce the risk of developing insulin resistance, make it a priority to exercise most days of the week. From Pilates to boxing to jogging, don’t be afraid to switch up your workout routine, since both aerobic exercises and weight training have different benefits for your health (a recent study from The British Journal of Sports Medicine found that a combination of 1-3 hours per week of aerobic exercise and 1-2 weight training sessions per week lowered mortality even more than doing just one). And remember that physical exercise is a little bit like learning to read or play the piano: doing it continuously over time has more benefits for keeping insulin resistance low compared to intense one-off workouts.
When you’re stressed, your body releases hormones like adreneline (which propels your nervous system into a “fight-or-flight” response) and cortisol, which triggers a quick release of glucose from your liver to give you an short-term energy boost. While these hormones play an essential biological role in survival, the chronic release of cortisol by your adrenal glands can actually hinder insulin secretion and lead to weight gain and even insulin resistance. You can improve how you manage stress levels by focusing both on long-term lifestyle shifts as well as building a catalogue of on-demand techniques that you implement as stress arises in your day-to-day life. This includes consistent exercise — one study performed on 185 university students found that only two days per week of aerobic exercise is linked to reduced anxiety — or mindfulness-centered practices such as yoga. According to research from 2018, making sure that you’re getting enough magnesium and vitamin B6 can also help lower perceived stress. Pumpkin seeds, almonds, and spinach are naturally high in magnesium, while beef liver, tuna, salmon, and chickpeas are good sources of vitamin B6.
Chronic stress is associated with a number of health consequences, including reduced neuroplasticity, disrupted immune response, and inflammation — which, in turn, can also impact the way your body releases insulin. While inflammation is something you might hear about frequently on social media, it’s an actual physiologic response, which can be caused by chronic conditions like lupus, extended exposure to toxins and pollutants, or infections and injuries. Chronic inflammation in adipose tissue is considered a crucial risk factor for developing insulin resistance. To lower the risk of inflammation, try eating foods with natural anti-inflammatory properties, like tomatoes, nuts, fatty fish, and fruits. You should also focus on incorporating healthy fats (like olive oil) into your diet. After dinner, you might want to head to the sauna, since research suggests spending time in a sauna can lower inflammation.
Gut microbiota are the microorganisms (including bacteria and archaea) that live in our digestive tracts, and they are integral to helping the body stay healthy. Each person has a unique set of microbiota that is determined by our DNA, but diet, weight, and external exposures can change our microbiome in a positive or negative way. Scientists have linked poor microbiome health to chronic diseases ranging from gastrointestinal inflammatory and metabolic conditions to neurological, cardiovascular, and respiratory illnesses. While research is still emerging, current findings indicate that a lack of proper gut microbiota may even disrupt intestinal permeability, which can lead to increased inflammation, impair insulin signaling, and even contribute to insulin resistance.
According to some researchers, eating more probiotic foods, including kefir, pickled vegetables, sauerkraut, miso, and kimchi, may boost healthy gut microbiota. It’s also key to consume foods that contain prebiotic fibers (such as garlic, onions, leeks, bananas, wheat, and oats) because they act as “food” for microorganisms and probiotics, and increase the number of friendly bacteria in your gut and help with digestive issues.
Getting a bad night’s sleep doesn’t just make you feel groggy and cranky — it can even increase your risk of developing insulin resistance. One study found that just one night of partial sleep deprivation induced insulin resistance in healthy individuals. Another study found that decreased sleep duration in healthy individuals was linked to impaired glucose homeostasis, but that “metabolic impairments induced by experiential sleep deprivation are reversible after sleep recovery in young and older adults.” Thankfully, if you’re finding it difficult to fall asleep, a few shifts in your daily habits can make a significant impact. Try cutting off caffeine at least 6 hours before bed (8-10 is even better), limit your exposure to melatonin-disrupting blue light in the evening, keep your bedroom temperature between 60 and 68 degrees Fahrenheit, and prevent light exposure during sleep with blackout curtains or eye masks that fit to the shape of your face. You might also want to try eating something with glycine (an amino acid that can help your body achieve deep sleep more quickly). Meat, fish, dairy, spinach, and legumes are all high in glycine and can be a great natural alternative to sleeping pills.
Neary 40% of adults worldwide are believed to have insulin resistance. But there’s good news: making conscious lifestyle choices can help improve your insulin sensitivity and even reverse the condition. We covered a lot of research and tips, but don’t feel the need to overhaul your entire lifestyle overnight. Hone in on 1-2 areas where you know you can improve, and apply some of the suggestions below:
Remember that change takes time. Take stock of your life and pick one of these areas to improve today. By consistently taking steps to lower your risk of insulin resistance, you can lead a healthier lifestyle.