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To understand insulin resistance (IR), you need to understand a bit about insulin.
Your pancreas produces insulin to help your cells use glucose for energy. When you have more glucose in your body, your pancreas makes more insulin so your cells can use it. Your insulin levels go up after meals to keep your blood glucose stable.
Insulin resistance is when your muscle, fat, and liver cells do not respond properly to insulin. Your pancreas compensates by making more and more insulin. Eventually, it will not be able to keep up, and your blood glucose levels will start to rise. This results in diabetes and other issues.
Type 2 diabetes follows insulin resistance. It develops when your pancreas cannot cope with the glucose in your body. Often the pancreatic cells that generate insulin become worn out from trying to compensate. This aggravates the situation as your pancreas produces less and less insulin.
Insulin resistance can cause obesity and be caused by it, resulting in a vicious cycle. IR makes it harder to lose weight, and the weight causes it to progress. While insulin resistance does not always become diabetes, it is a common precursor. It can also potentially lead to other problems, such as cardiovascular disease.
The underlying cause of insulin resistance is poorly understood. It appears to be related to excess weight and lack of physical activity, but scientists are yet to pin down the biological mechanism. One theory is that high free fatty acid in your blood impairs insulin signaling.
Another idea is related to high fructose consumption. Multiple factors are likely involved, and the cause may not be the same for everyone. However, there are several risk factors.
Risk factors for insulin resistance include:
There are links¹ between obesity and insulin resistance because of the hormones and cytokines released by adipose tissue. These appear to contribute to insulin resistance.
Being sedentary tends to lead to excess weight. Physical activity burns energy and increases insulin sensitivity by making your cells hungry for glucose. Physical inactivity may directly cause insulin resistance. When you ask your muscles to do less, they may reject unneeded energy.
You are at higher risk of insulin resistance if somebody in your family also has insulin resistance. Scientists have identified some specific genes.² You are particularly at risk if a parent or sibling has type 2 diabetes or prediabetes.
Black, Hispanic, and Asian people are at higher risk of insulin resistance.
If you’ve had gestational diabetes or given birth to a baby who weighed more than 9lbs, you’re more at risk of insulin resistance.
Other risk factors include:
High levels of dietary carbohydrates or sugars
Low good cholesterol
Some of these risk factors can be controlled with lifestyle changes, while others cannot.
One of the insidious things about insulin resistance is that it typically has no symptoms until blood sugar has become extremely elevated. At this point, you’ll notice classic diabetes symptoms such as excessive thirst.
Some people may experience acanthosis nigricans,³ a darkening of the skin in the armpit and on the back and sides of the neck, often accompanied by skin tags. This condition is considerably more common in Black people. A few people might have eye changes, as diabetic retinopathy can set in with relatively small blood sugar changes.
As most people with insulin resistance have no symptoms, your doctor will diagnose it with tests.
Most people find out that they are insulin resistant during routine testing. The recommendation from the U.S. Preventive Task Force⁴ is to screen for elevated blood sugar in adults 35-70 years old who are overweight or obese. People with strong risk factors such as genetics may need to be checked younger or more often.
You should have this test repeated every three years if your results are normal. Screening is also essential for people who have had gestational diabetes or given birth to a high birth weight baby.
If you are gaining weight, it might be worth having your doctor check you for prediabetes, as weight gain can be a symptom and cause. Many people have insulin resistance and don't know it. You can sometimes be insulin resistant for many years without developing any symptoms.
While there is a direct test for insulin resistance, it is expensive and complicated, and doctors rarely use it outside of a research environment. The test is the hyperinsulinemic-euglycemic clamp technique.⁵
Most other tests require IV access and multiple venipunctures in a hospital or clinic. The oral glucose tolerance test, sometimes used to confirm diabetes, does not require an IV. However, it requires a fair bit of time and multiple blood samples.
Insulin resistance has few or no symptoms, and there is insufficient evidence that addressing it is beneficial. Therefore, doctors seldom test for insulin resistance directly.
Instead, doctors keep an eye on your fasting plasma glucose and good and bad cholesterol levels, which can show insulin resistance fairly early. Often, insulin resistance is not apparent until it has progressed to prediabetes, characterized by A1C levels of 5.7-6.4% and fasting plasma glucose of 100-125 mg/dL.
Thankfully, even in the prediabetes phase, it is possible to bring your blood sugar under control and potentially "reverse" the condition with the right combination of diet and exercise.
The good news is that developing diabetes is not inevitable after a diagnosis of insulin resistance. IR is perfectly manageable, and you can stop it from progressing to diabetes.
The primary treatment for insulin resistance is exercise. Getting active makes your cells more sensitive to insulin and can prevent IR from progressing further. Choose a physical activity you enjoy and will keep up. Aim for thirty minutes a day of moderate-intensity physical activity most days of the week. This includes brisk walking.
Some people can get enough exercise without needing to "work out.” For example, they may consistently park further away from the office or get off the bus a stop early. If you are disabled or have mobility challenges, ask your doctor to refer you to a physical therapist to develop an exercise program that works for you.
Remember that the best exercise is the one you will actually do. Many people start an exercise plan with good intentions but give up because it feels like a chore.
Other steps that you can take include:
Crash dieting is entirely unhelpful: very low-calorie diets may actually cause insulin resistance. Aim for sustainable lifestyle changes rather than dieting. Avoiding refined sugars can be particularly helpful; limit sugary foods and beverages to an occasional treat.
Consume more dietary fiber from natural sources. The easiest way to do this? Switch to whole grains. Research has linked high-fiber diets with lower rates of insulin resistance, hypertension, hyperlipidemia, and cardiovascular disease. Fiber is also good for your digestive system.
Make sure you get enough sleep.⁶ Restricted sleep is associated with insulin resistance. If you have sleep difficulties, talk to your doctor so they can get to the bottom of the problem.
There is no medication recommended for insulin resistance. Although metformin increases insulin sensitivity, it is not labeled or recommended for isolated insulin resistance. There's limited evidence that treating insulin resistance before it becomes prediabetes helps.
This guidance is helpful for most people for their overall health. Whether or not you have IR, it is a good idea to get and stay more active, control your weight, and think about what you eat.
These choices can delay or even stop the progression from insulin resistance to prediabetes. They can even reverse prediabetes to a point.
As with treatment, the best way to prevent insulin resistance is to stay active and eat a healthy diet. These are the strongest controllable risk factors for insulin resistance. They are crucial if you have uncontrollable risk factors such as genetics.
As scientists poorly understand the mechanism of insulin resistance, there are only a few specific recommendations. A healthy lifestyle is your best bet for avoiding developing insulin resistance and related conditions such as diabetes. We know that excess body weight, especially belly fat, is a strong contributor.
While controlling weight is a challenge and should not become an obsession, staying "in shape" is the only way to prevent insulin resistance.
Talk to your doctor if you have acanthosis nigricans. Otherwise, you should speak to your doctor about blood sugar screening every three years, starting at 35, if you are overweight or obese. Your doctor may recommend starting younger or testing more often if you have major risk factors such as obesity or a parent or sibling with type 2 diabetes.
If you have insulin resistance, you should have your fasting blood sugar tested as recommended by your physician. They might also recommend an oral glucose tolerance test, which is a little more involved, but can spot smaller changes.
Insulin resistance is when your cells stop responding to insulin and properly taking up glucose. This leads to your pancreas working harder and can eventually result in it producing less insulin.
While insulin resistance does not inevitably lead to diabetes, it is a strong precursor. There is currently no medication for insulin resistance, but doctors typically recommend increasing physical activity and eating fewer sugars and more fiber. If you’re at high risk of developing diabetes, your doctor should screen you regularly to check for insulin resistance and prediabetes.
Prediabetes and type 2 diabetes: Screening | U.S. Preventing Services
Measuring insulin resistance | Collage of Medicine
Insulin resistance & prediabetes | National Institute of Health
Small amounts of liver fat lead to insulin resistance and increased cardiometabolic risk factors | Yale School of Medicine
Insulin resistance syndrome | American Family Physician