Insulin: What It Does, Why It Matters, and How to Optimize Your Levels
When you think of insulin, you probably think of diabetes. But what if this hormone was influencing your metabolism, energy levels, and long-term health in ways you didn’t realize?
Insulin—best known for shuttling glucose from the bloodstream into cells—plays a critical role beyond blood sugar regulation. In fact, insulin resistance is implicated in conditions like heart disease, cognitive decline, and infertility. And here’s the surprising part: even if your glucose and HbA1c levels are normal, your insulin levels could still be elevated, quietly impacting your health. Learning to optimize insulin isn’t just for those with diabetes—it’s essential for everyone striving for optimal well-being and disease prevention.
What Does Insulin Do in the Body?
Insulin is a hormone produced by the pancreas that plays a critical role in every cell of your body. Its primary job is to allow glucose—the body’s main energy source—to enter cells. But insulin’s influence goes far beyond blood sugar regulation. It impacts:
Energy storage – Helps store excess glucose as glycogen or fat
Muscle and bone health – Supports skeletal muscle growth and bone development
Fat metabolism – Regulates how the body stores and burns fat
Brain function – Affects neuron growth, cognition, and memory processing
Hormone balance – Supports normal sex hormone production in the testicles and ovaries
Kidney function – Regulates sodium absorption, influencing blood pressure
Among its many roles, insulin’s most well-known function is managing blood sugar levels. When you eat, carbohydrates break down into glucose, raising blood sugar. In response, insulin acts as a master key, unlocking cells so glucose can enter and fuel the body. While some cells, like those in the liver, don’t require insulin to absorb glucose, they still rely on insulin signaling to store excess glucose as glycogen for later use.
What Happens When Insulin Stops Working?
When cells become insulin-resistant, this "key" mechanism starts to fail. The lock—a protein called Glucose Transporter Type 4 (GLUT4)—no longer responds properly to insulin. As a result, glucose builds up in the bloodstream instead of entering cells. In response, the pancreas produces more insulin in an attempt to overcome this resistance. Over time, this cycle worsens, leading to chronically high insulin levels that drive metabolic dysfunction.
Insulin resistance isn’t just a concern for those with diabetes—it plays a role in weight gain, metabolic disorders, and even longevity. Research suggests it contributes to chronic inflammation and increases the risk of diseases like heart disease, Alzheimer’s, and certain cancers, including breast cancer, due to the promotion of cell growth and chronic inflammation (Srinivasan et al., 2022).
As you can see, insulin is a major player in our health– supporting metabolism, hormone balance, and disease prevention. Understanding how to optimize insulin function can be a key factor in maintaining long-term well-being.
What’s Considered a Normal Insulin Level?
There isn’t a universal standard for “normal” insulin levels. Many reference ranges define fasting plasma insulin below 25 µU/mL as normal (John & Anastasopoulou, 2024). However, research suggests that this threshold may be too high. One study on individuals without diabetes found that fasting insulin levels above 10.57 µU/mL were more common in those with metabolic syndrome (Lee et al., 2006). Other experts argue that an optimal range is even lower—between 2-6 µU/mL, which is the target we aim for at GreenMind (Bikman, 2023).
Why Isn’t There an Established Optimal Level for Insulin?
Historically, high insulin was viewed as a consequence of illness rather than a cause. However, growing evidence suggests that hyperinsulinemia plays a direct role in obesity, type 2 diabetes, cardiovascular disease, and even reduced life expectancy (Kolb et al., 2020).
You might be wondering: Do my insulin levels matter if my glucose and HbA1c are normal? The answer is yes. Chronically elevated insulin often develops years before blood sugar issues arise. One study found that HOMA β-cell function values increased sharply 3-4 years before a diabetes diagnosis (Tabák et al., 2009). HOMA-B is a calculated marker that uses fasting insulin and glucose levels to assess pancreatic function. Therefore, it provides an early warning sign—long before blood sugar alone reveals a problem.
High fasting insulin is often a red flag for future metabolic dysfunction and may indicate:
Early insulin resistance – Your body requires more insulin to maintain stable blood sugar.
Increased risk for type 2 diabetes – Chronic hyperinsulinemia can lead to pancreatic beta-cell burnout from producing so much insulin.
Weight gain & difficulty losing fat – High insulin promotes fat storage, especially around the midsection.
Higher inflammation & cardiovascular risk – Linked to elevated triglycerides, low HDL ("good" cholesterol), and high blood pressure.
PCOS & hormonal imbalances – Insulin resistance is a key driver of polycystic ovary syndrome and can affect hormonal and fertility health.
Since insulin resistance can develop silently, testing fasting insulin levels can be a powerful tool for preventing chronic disease before it takes hold.
What You Can Do to Lower Elevated Insulin Levels:
1. Increase Protein Intake
Protein helps reduce cravings, promotes satiety, and reduces blood sugar spikes for better blood sugar regulation. Plus, a more protein-rich diet helps tell your liver to release stored glucose when your blood sugar gets low, preventing energy crashes and irritability in between meals when your blood sugar starts to drop.
Prioritize lean proteins like chicken, fish, eggs, Greek yogurt, and light portions of legumes (lentils, beans, chickpeas, edamame).
Need a quick snack? Try out our yummy protein ball recipe!
2. Eat More Fiber
Fiber is crucial for managing blood sugar and insulin levels in more ways than one. Soluble fiber (found in foods like oats, lentils, apples, citrus fruits, berries, flax, and chia seeds) forms a gel-like substance that slows glucose release, while insoluble fiber (present in vegetables, nuts, seeds, and even fruit and legume skins) adds bulk to your stool and promotes smooth digestion. Virtually any veggie does the trick–from tomatoes and mushrooms to spinach, artichokes, sauerkraut, lettuce, zucchini, bell peppers, and broccoli–each contributing its own fiber "magic" to help lower insulin spikes.
Plus, because our bodies can’t digest fiber, it reaches the large intestine, where it feeds beneficial gut bacteria, producing short-chain fatty acids that support overall gut health and improve insulin sensitivity. As an added bonus, some starchy foods (like rice, potatoes, and oats) can be transformed into resistant starch, which acts like fiber. This happens by cooking and then cooling them, making them harder to digest so that less glucose is absorbed. Fiber can not only balance out glucose levels but also enhance the body’s insulin response, keeping energy levels steady and supporting long-term metabolic health.
Aim for 25–35g of fiber daily from vegetables, berries, legumes, nuts, and seeds. When increasing your fiber intake, make sure to start slowly if you’re not used to consuming a lot of fiber or if you notice any bloating or GI discomfort when increasing your intake.
Be sure to stay hydrated when consuming a high-fiber diet to prevent worsening constipation.
3. Create a Balanced Plate
To avoid spiking insulin, make sure that every meal or snack is balanced and rich in protein, fiber, and healthy fats. We teach the simple rule: “no naked carbs” for all meals or snacks.
Always ensure your plate has:
Protein (pasture-raised chicken, wild-caught fish, tofu, lentils, grass-fed beef, Greek yogurt, etc.)
Non-Starchy Carbohydrates (broccoli, salad greens, asparagus, tomatoes, peppers, onions, spinach, zucchini, etc.)
Healthy Fats (avocados, nuts, olive oil, etc.)
4. Get Your Heart Rate Up
Cardio exercise, specifically zone 2 cardio, improves insulin sensitivity by increasing glucose uptake in your muscles reducing elevated insulin levels (Romeres et al., 2021). Zone 2 cardio is 60-70% of your maximum heart rate, which is something that you can sustain for at least 30 minutes.
Aim for zone 2 exercise on a weekly basis, such as running, swimming, hiking uphill, rowing, or cycling.
Aim to incorporate strength training at least 2-3 times a week in addition to cardio! Muscle tissue increases insulin sensitivity, reducing the amount of insulin your body needs.
5. Move Your Muscles After Meals
Any type of movement after meals is beneficial for promoting blood sugar regulation because it activates GLUT4 – the lock on cells controlling glucose uptake – allowing more glucose to enter the cell, improving insulin sensitivity.
Get moving after meals! Even a 10-20 minute post-meal walk has benefits for preventing an insulin spike. You can also do a short exercise routine such as a few calf raises, pushups, or squats.
6. Prioritize Sleep
Poor sleep and short sleep duration can actually promote insulin resistance and encourage inflammation (Singh et al., 2022). Lack of sleep can elevate cortisol production – one of your primary stress hormones. High cortisol then promotes abdominal fat storage, which is linked to insulin resistance. Lack of sleep can also disrupt your hunger hormones, increasing cravings for high-carb and sugary foods while reducing your satiety hormone, leptin.
Aim for 7–9 hours of quality sleep each night.
Establish a nightly routine to wind down at the end of the day. Avoid screens and wear blue light glasses for two hours before bedtime, use blackout curtains to ensure a completely dark bedroom, take a warm bath or shower before bed, drink valerian root tea, or read a book. Find a routine that works for you and signals to your body that it’s time to sleep.
7. Manage Stress
Chronic stress raises cortisol, putting your body in a state of persistent low-grade inflammation, which can elevate insulin levels and lead to insulin resistance.
Incorporate meditation, 4-7-8 breathing, journaling, or yoga into your daily routine.
Spend more time in nature. Try going for a post-meal walk, having a friend or family picnic, and get 5-10 minutes of sunshine when you first wake up.
Insulin impacts so much more than just blood sugar—it affects our metabolism, energy, and even brain function. When insulin resistance develops, it can lead to serious health issues, but the good news is, you can take steps today to keep your insulin levels within an optimal range. Simple lifestyle changes—like eating more protein and fiber, staying active, getting better sleep, and managing stress can make all the difference!
Want to take action?
We run fasting insulin levels on most of our patients and can provide support and strategies to improve your metabolic health and optimize your overall well-being for good. You can get started today with a complimentary nutrition consult. We’d love to hear from you!
Sources
Bikman, B. (2023). What are normal levels of insulin and why don’t we test it more? Levels. https://www.levels.com/blog/what-are-normal-insulin-levels-and-why-dont-we-test-it-more
John, T., & Anastasopoulou, C. (2024). Insulin. Medscape. https://emedicine.medscape.com/article/2089224
Kolb, H., Kempf, K., Röhling, M., & Martin, S. (2020). Insulin: too much of a good thing is bad. BMC Medicine, 18(1). https://doi.org/10.1186/s12916-020-01688-6
Lee, S., Choi, S., Kim, H. J., Chung, Y. S., Lee, K. W., Lee, H. C., Huh, K. B., & Kim, D. J. (2006). Cutoff values of surrogate measures of insulin resistance for metabolic syndrome in Korean non-diabetic adults. Journal of Korean Medical Science, 21(4), 695–700. https://doi.org/10.3346/jkms.2006.21.4.695
Romeres, D., Schiavon, M., Basu, A., Cobelli, C., Basu, R., & Dalla Man, C. (2021). Exercise effect on insulin-dependent and insulin-independent glucose utilization in healthy individuals and individuals with type 1 diabetes: a modeling study. American Journal of Physiology. Endocrinology and Metabolism, 321(1). https://doi.org/10.1152/ajpendo.00084.2021
Singh, T., Ahmed, T. H., Mohamed, N., Elhaj, M. S., Mohammed, Z., Paulsingh, C. N., Mohamed, M. B., & Khan, S. (2022). Does insufficient sleep increase the risk of developing insulin resistance: a systematic review. Cureus, 14(3). https://doi.org/10.7759/cureus.23501
Srinivasan, M., Arzoun, H., Gk, L. B., & Thangaraj, S. R. (2022). A systematic review: does insulin resistance affect the risk and survival outcome of breast cancer in women?. Cureus, 14(1). https://doi.org/10.7759/cureus.21712
Tabák, A. G., Jokela, M., Akbaraly, T. N., Brunner, E. J., Kivimäki, M., & Witte, D. R. (2009). Trajectories of glycaemia, insulin sensitivity, and insulin secretion before diagnosis of type 2 diabetes: An analysis from the Whitehall II Study. The Lancet, 373(9682), 2215–2221. https://doi.org/10.1016/s0140-6736(09)60619-x