How to improve insulin sensitivity

One key to maintaining healthy, stable blood sugar levels and optimizing metabolic health is being insulin-sensitive. The reason: The more sensitive, or responsive, your cells are to insulin, the more efficiently this hormone can transport excess glucose from the bloodstream into cells where it can be immediately used for energy or stored for later. On the other hand, a lack of insulin sensitivity (known as insulin resistance) makes it harder for glucose to enter cells, contributing to elevations in blood glucose that can wreak havoc on metabolic health.

Fortunately, many habits that support healthy blood glucose also support insulin sensitivity. Below, learn the basics of insulin’s role in the body, what contributes to insulin resistance, and simple diet and lifestyle hacks to boost insulin sensitivity.

What Is Insulin Sensitivity?

Insulin sensitivity describes how responsive your cells are to the effects of the hormone insulin. To appreciate what this means, let’s recap the role of insulin in the body: Normally, when blood sugar levels rise after eating a carbohydrate-containing food, the pancreas secretes a corresponding amount of insulin, which binds to receptors on muscle, adipose (fat), and liver cells and acts like a key to “unlock” these cells, allowing them to absorb glucose. Specifically, insulin triggers a cellular signaling cascade that prompts GLUT4 glucose transporters to travel from the interior to the surface of cells, where they help take up glucose from the bloodstream. Your cells then use glucose as an immediate source of energy or store it as glycogen or fat.

The release of insulin after carbohydrate consumption and the subsequent glucose uptake by cells allows blood glucose levels to fall back to a safe range after you eat—and this process can only occur effectively when you are insulin-sensitive. In other words, insulin sensitivity is an essential precursor for healthy blood glucose levels.

When insulin sensitivity is compromised, your cells are somewhat “numb” to its effects, and your pancreas must release more insulin (leading to hyperinsulinemia) to have the same impact—which is known as insulin resistance. What do we mean by numb? When cells are insulin resistant, the insulin-induced translocation of GLUT4 to the cell surface is blunted, and more insulin is required to overcome this and adequately lower blood sugar. A variety of lifestyle factors have been implicated in insulin resistance (some of which are outlined below), but the exact mechanisms by which each of these impair GLUT4 translocation are somewhat unclear and likely vary, as there are many different cellular processes involved in insulin signaling and GLUT4 transport—and alterations in any number of these could potentially play a role.

As long as the pancreas releases enough insulin to compensate for your cells’ weak response to the hormone, blood sugar remains in a normal range. But if insulin sensitivity continues to decline, the pancreas can no longer make enough insulin to keep up with your body’s demand and blood glucose will remain chronically elevated. Initially, that becomes prediabetes, one of the first clinical indications of insulin resistance, but can eventually evolve into Type 2 diabetes, which is a state of advanced insulin resistance. (Type 1 diabetes is a chronic disease in which the pancreas makes little to no insulin, requiring exogenous insulin.)

Together, the high blood glucose and insulin that result from insulin resistance can be very damaging, promoting oxidative stress and inflammation, and making it more likely that you will experience Type 2 diabetes, weight gain, metabolic syndrome, cardiovascular disease, non-alcoholic fatty liver disease (NAFLD), polycystic ovarian syndrome (PCOS), and more.

What causes insulin sensitivity to decline?

Insulin sensitivity exists on a spectrum—and certain habits can make you more or less insulin-sensitive. Anything that consistently spikes blood sugar levels will put extra stress on the pancreas to produce more insulin and, over time, contribute to insulin resistance. As you’d suspect, this includes regularly consuming a diet high in processed, refined carbs, and sugars.

“When a process is excessively activated—repeated glucose spikes from eating sugary foods leads to repeated insulin surges to clear the glucose—the body will often dampen its response to reduce the activation,” says Ben Bikman, PhD, a Levels advisor and expert on insulin resistance. “Think of how a caffeine addict needs more caffeine than they used to.”

However, other factors beyond diet can significantly contribute to declining insulin sensitivity, including high-stress levels, poor sleep, low physical activity levels, and inflammation.

• Excess body fat, particularly abdominal fat, releases inflammatory molecules called adipokines (e.g. TNFα and IL-6) that have been shown to interfere with insulin signaling and adipose tissue metabolism, which may promote systemic insulin resistance. Insulin resistance can also contribute to even more inflammation, creating a vicious cycle.
• Both stress and poor sleep raise “stress hormones” like cortisol and epinephrine, which can raise blood glucose levels by mobilizing the release of stored glucose into the bloodstream and ramping up the liver’s glucose production. Stress hormones also counter the effect of insulin, so more insulin is needed to lower blood glucose—and, as mentioned, repeated insulin surges contribute to insulin resistance.
• Physical activity is one of the best ways to lower blood glucose and improve insulin sensitivity, as it prompts skeletal muscle cells to absorb more glucose without the need for additional insulin, but a lack of physical activity can have the opposite effect and increase insulin resistance.

Ways to Improve Insulin Sensitivity

Fortunately, insulin resistance is reversible—and some of the most powerful habits to improve insulin sensitivity are things you may already be doing to keep blood glucose in check:

Exercise

All forms of exercise—resistance training, aerobic exercise, or a combination—effectively improve insulin sensitivity and support healthy blood glucose levels. That’s because when your muscles contract, GLUT4 glucose transporters move from the interior of muscle cells to the surface of cell membranes, prompting these cells to absorb more glucose from the bloodstream without requiring more insulin release. In fact, some research suggests exercise makes cells more insulin sensitive (and helps lower blood glucose) for 24 hours after a workout.

In general, the more you exercise, the more you’ll benefit: People engaging in 170 minutes of exercise per week (or 24 minutes per day) over 6 months improved insulin sensitivity by 85%, while those engaging in 115 minutes per week improved insulin sensitivity by 40%, per one study. Consistency is also crucial: Another study found that even among highly fit people, taking 10 days off of exercise led to a decline in insulin sensitivity. Fortunately, it was quickly restored when regular exercise resumed. Exercise may also boost insulin sensitivity by reducing inflammation. Several studies have shown a relationship between regular exercise, reduced markers of inflammation, and improved insulin sensitivity—which may be of particular benefit to people with obesity (a chronic proinflammatory state) and other inflammatory conditions.

Eat low-carb

Eating fewer carbohydrates in general—particularly highly processed or refined carbs and sugars that are broken down and absorbed rapidly by the body—is one of the best ways to buffer the blood sugar spikes and subsequent surges in insulin that can lead to insulin resistance. Various iterations of low-carb, high-fat diets (ranging from 10%-43% of total calories from carbs) have been shown to improve insulin sensitivity among metabolically vulnerable groups, including women with PCOS (in this study and this study) and older adults with obesity.

One potential mechanism for this effect: Low-carb diets have been shown to increase production of a hormone secreted by fat tissue called adiponectin, which supports insulin sensitivity and insulin secretion, curbs glucose production by the liver, helps prevent the accumulation of dangerous visceral fat, and lowers inflammation. While an ideal macronutrient ratio for boosting insulin sensitivity hasn’t been established, this study found a significant increase in adiponectin levels with diets containing <30% of calories from carbohydrates.

Eat colorful plants and healthy fats

Inflammation—whether caused by excess body fat, infections like the flu, or autoimmune disorders—is associated with decreased insulin sensitivity, partly because the various molecules associated with unhealthy inflammation interfere with normal insulin signaling.

One way to combat inflammation is by upgrading your diet—not just to contain fewer carbs, but to contain more colorful plant foods and healthy fats, too. Colorful plant foods (think: dark leafy greens, purple cabbage, red bell peppers, berries, herbs, spices) contain a variety of beneficial compounds such as carotenoids and polyphenols that have been shown to curb inflammation as well as oxidative stress, both of which can precede insulin resistance. These compounds appear to exert their beneficial effects in the body, in part, by downregulating the NF-κB pathway that turns on proinflammatory genes and activating the Nrf2 pathway that activates genes known to enhance antioxidant defenses. Swapping out questionable sources of fat (think: highly refined vegetable and seed oils) for well-established healthy fats like extra virgin olive oil, avocado oil, fatty fish, and walnuts may also help curb excessive inflammation.

Greater adherence to a Mediterranean-style diet—which emphasizes a variety of plant foods and healthy fats—has been associated with decreased inflammation and insulin resistance and improved insulin sensitivity in people with overweight and obesity.

Consider fasting

Time-restricted feeding (TRF), in which you consume all food in a predetermined “eating window,” is an approachable form of fasting linked to various metabolic health benefits. In a 2023 meta-analysis of 12 studies, which included adult men and women among them, researchers compared the effects of early vs late TRF eating windows lasting 6-10 hours. Whether the eating window was earlier or later in the day, participants tended to experience reductions in body weight and insulin resistance, and earlier eating windows (e.g., 7 am to 3 pm) were even more strongly associated with improved insulin sensitivity and glucose metabolism.

By not eating at all hours of the day, you are giving your pancreas a break from cranking out insulin, which allows blood insulin levels to drop. This drop in insulin not only helps prevent the hyperinsulinemia that precedes insulin resistance, but it also allows your body to burn fat more efficiently as a fuel source since high insulin levels promote fat storage.

Find ways to manage stress

During times of stress, a component of the body’s autonomic nervous system (ANS) called the sympathetic nervous system is activated and triggers your fight-or-flight response, which prompts the release of stress hormones like cortisol and epinephrine. As previously mentioned, these stress hormones have blood sugar-elevating and insulin-suppressing properties, and chronic stress has been associated with increased risk of insulin resistance and diabetes.

Fortunately, strategically engaging the other half of the ANS, known as the parasympathetic or rest-and-digest nervous system, can counter these effects and possibly improve glucose tolerance and insulin sensitivity. So, how do you activate it? Regular physical activity and recovery, having a social support system, and practicing relaxation and mindfulness techniques (e.g., deep breathing exercises, gentle stretching, meditation) may all help.

Next time you’re stressed, try this 3-minute body scan meditation to help bring your awareness inward and instantly feel more grounded.

Prioritize sleep

Inadequate sleep is associated with reduced insulin sensitivity, and it only takes a few nights of subpar shuteye to cause problems. A study on healthy adult men found that six nights of sleep deprivation (4 hours per night) led to a 40% slower glucose clearance from the bloodstream after an oral glucose tolerance test, suggesting that cells were not as responsive to the glucose-lowering effects of insulin.

Like stress, inadequate sleep can promote insulin resistance by activating the sympathetic nervous system and driving up levels of stress hormones like cortisol.

Aim for 7-8 hours of sleep per night and boost your likelihood of getting quality sleep by practicing good sleep hygiene: follow a consistent bedtime routine, avoid electronic screens several hours before bed, stop drinking alcohol at least four hours before bed, keep your room cool and dark, and only use your bed for sleeping (avoid scrolling or watching TV).