What Is Insulin Resistance and How Do I Know If I Have It?

Many women begin noticing frustrating metabolic changes in their 40s and 50s. Weight that used to come off easily starts to stick, no matter how hard you try to get it off. Energy crashes after meals. Cravings for carbohydrates start to increase. Blood pressure or cholesterol numbers begin to creep up. What you might not realize is that all these seemingly disparate changes are actually part of a larger problem: insulin resistance.

Insulin resistance is one of the most frequent metabolic problems to develop in midlife, yet many people have never had it explained clearly. Understanding what insulin resistance actually is, and how to recognize it, can make a significant difference in long-term health.

In this article, we’ll look at what insulin resistance actually means biologically, how it develops, how to recognize the signs, and when it makes sense to evaluate it medically.

What is happening biologically?

Insulin is a hormone produced by the pancreas. Its main job is to help move glucose (sugar) from the bloodstream into cells, where it can be used for energy.

When someone has high insulin sensitivity (i.e., a normal metabolism), this system works very efficiently. After eating, insulin and blood sugar rises appropriately, glucose (blood sugar) moves into the muscles and other tissues with the help of insulin, and blood sugar then returns to a normal level.

Insulin resistance is what happens when the body’s cells become less responsive to insulin’s signal.

When this happens, the pancreas has to produce larger and larger amounts of insulin just to keep blood sugar levels stable. For a long time, blood sugar levels may still appear “normal” on labwork, but insulin levels are actually rising in the body.

This leads to many problematic metabolic changes:

• Muscle tissue becomes less efficient at using glucose

• The liver produces more glucose overnight

• Fat storage increases, particularly around the abdomen, and particularly in the form of visceral fat (the dangerous kind for your health)

• Overall inflammation increases in the body

This is why insulin resistance often shows up first as gradual weight gain, especially in the belly (abdominal) region.

In women, unfortunately the perimenopause transition can worsen and accelerate this process. Declining estrogen levels decrease muscle mass, change fat distribution unfavorably, and directly affect insulin signaling. Muscles are one of the best ways for our bodies to "dispose" of extra glucose coming in. More muscle means a larger "metabolic sink" for to send incoming blood sugar too. So when we lose muscle mass, that further reduces the body’s ability to get rid of glucose efficiently, which further contributes to insulin resistance.

Sleep disruption, chronic stress, and reduced physical activity can further aggravate insulin resistance through hormonal pathways that will be discussed in other articles.

Why common advice to "eat less and exercise more" often fails

Many people with insulin resistance are told simply to “eat less and exercise more.” While well intentioned, that advice often fails because it does not fully address the underlying physiology.

For example, many women increase cardio exercise in response to weight gain or new belly fat. While cardio has clear cardiovascular benefits, excessive cardio without resistance training can contribute to muscle loss over time. Since muscle is the body’s largest site for glucose disposal, losing muscle through excessive cardio can directly worsen insulin resistance.

I had a patient last week who was a marathon runner. She was in her early 40's and actually had a normal body weight, but she did very little resistance training (I'm talking yoga or pilates once in a blue moon, mostly just to keep her muscles limber for running). She had a very strong family history of diabetes. When I checked her hemoglobin A1c and fasting glucose, it was technically normal, though on the high side of "normal." But when I checked her fasting insulin level, the level was clearly elevated, and explained that she was actually at risk for developing prediabetes and eventually diabetes down the road. While some of that is certainly genetic, a lot of it is modifiable with adjustment of her lifestyle. She was already highly motivated and disciplined. No one can train for a marathon without those qualities. We just needed to shift some of that motivation and discipline toward strength training (and supporting that strength training with adequate nutrition specifically focused on building muscle and optimizing metabolic health), rather than spending it all on cardio.

Just a note here as well: undereating can also backfire, for similar reasons. Severe calorie restriction can lead to metabolic adaptation and difficulty maintaining lean muscle mass. Muscle is "expensive" to maintain. If you go into a calorie deficit without prioritizing maintaining muscle, you are just asking to lose muscle tissue and eventually set yourself up for insulin resistance when you try to return to your regular diet. That's why I do not prescribe GLP-1 medications without ensuring that women are also getting adequate nutrition to support their lean body mass and also making an effort to strength train regularly. This counteracts the tendency towards muscle loss that will happen otherwise when on a restricted calorie intake.

Another common issue I see is focusing only on body weight rather than body composition. Body weight, and BMI as a measure, is essentially worthless to me. Body composition is what matters. Two women can weigh exactly the same but have very different metabolic health depending on their muscle mass and visceral fat levels.

Evidence-based strategies that actually help with insulin sensitivity and reverse insulin resistance

The encouraging news is that insulin resistance is often very responsive to targeted metabolic interventions.

One of the most effective lifestyle-based strategies is resistance training. Building and maintaining muscle gradually improves insulin sensitivity because muscle tissue acts as a major site for blood sugar disposal. Even just two short resistance sessions per week can significantly improve metabolic health.

Adequate protein intake also plays an important role. Protein supports muscle maintenance and helps regulate appetite and blood sugar stability.

Sleep quality is another critical factor that is too often overlooked. And it's one that is often a factor in perimenopause and menopause, when hormonal changes and hot flashes make sleep fragmented and disrupted. Unfortunately, poor sleep increases cortisol and directly causes insulin resistance, making a healthy metabolism and body composition so much harder to manage long term.

Of course, aside from lifestyle factors, there are medications and supplements that can be helpful in support of these goals. Not just to treat the insulin resistance, but to support healthy sleep and a healthy hormone balance.

In many cases, a structured metabolic evaluation is helpful. This may include looking at fasting insulin levels, glucose patterns, lipid markers, and other indicators of metabolic health. These measurements can provide a clearer picture of how well the body is responding to insulin.

When identified early, insulin resistance can usually be improved through a combination of strength training, nutrition strategies, sleep optimization, and targeted medical support when appropriate.

When it makes sense to seek medical evaluation for blood sugar issues

Many people assume they would "feel it" if they had insulin resistance, but that's not always the case. It more often develops gradually over years, so testing early is the best way to catch it. This is doubly true if you have a family history of diabetes, since diabetes has a strong genetic component.

Some common signs that may suggest insulin resistance include:

• Gradual weight gain, especially around the abdomen

• Difficulty losing weight despite regular exercise

• Fatigue or energy dips after meals

• Increased sugar or carbohydrate cravings

• Elevated triglycerides and/or low HDL cholesterol

• Rising blood pressure

• Being told you have prediabetes at your regular check up

In these situations, a comprehensive medical evaluation will help determine whether insulin resistance is contributing to symptoms. Identifying it early can allow for targeted strategies that improve metabolic health before more serious conditions such as type 2 diabetes develop.

To summarize:

Insulin resistance is one of the most common metabolic changes that develops during midlife, particularly for women navigating hormonal shifts and gradual muscle loss.

These changes are rarely about willpower or personal discipline. Eating less or exercising more without a strategy is NOT the answer. Insulin resistance more often reflects shifts in muscle mass, hormone signaling, sleep patterns, and overall metabolic health. Focusing on these patterns and treating them when appropriate can reverse early insulin resistance and improve your healthspan.