Metabolic health is a principal component of healthspan. It directly influences energy levels, weight management, chronic disease risk, and overall quality of life. Understanding the state of your metabolic health is a critical component of proactive care.
But what exactly is metabolism? Metabolism refers to the chemical processes in the body necessary to function properly. These reactions involve breaking down the food you eat into energy to fuel cells and support functions like breathing and digestion.
A fasting insulin blood test offers unique insight into quantifying metabolic health. Fasting insulin is often associated with diabetes, as type 2 diabetes is a condition of insulin dysfunction that currently affects an estimated 37.3 million people in the US. [1] But this hormone is linked to even more physiological processes and health outcomes than diabetes because it acts on every cell in the body. For example, insulin levels influence cognition, heart health, and sleep. [2] Insulin impacts healthspan—the number of years spent in good health—in many ways through its influence on chronic disease risk. So, managing fasting insulin levels can delay the risk of developing chronic diseases throughout the lifespan.
Despite its importance, healthcare providers don't often include fasting insulin in blood panels for healthy adults. Because it plays a central role in metabolic health and healthspan, InsideTracker now includes fasting insulin levels as part of its Ultimate Plan.
Let's take a closer look at why insulin is at the center of metabolic health.
The pancreas releases hormones when blood glucose levels are high (like after a meal) to usher glucose from the bloodstream into cells to either be used for energy or stored as energy for later. Every cell and every organ in the body can uptake glucose and is sensitive—or responsive—to insulin. But chronically high levels of insulin in the blood (that occur when blood glucose levels remain consistently high) cause cells to be less responsive to insulin's action, leading to insulin resistance.
Imagine your body's cells are like doors, and insulin is the key that unlocks these doors to let glucose inside. Insulin resistance is like having doors with faulty locks that become less responsive to the key. As a result, the doors struggle to open and allow glucose inside, causing blood glucose levels to remain high. High blood sugar then signals the pancreas to release more insulin. This creates excess blood glucose and excess insulin. As cells lose sensitivity, insulin resistance occurs.
Insulin resistance is believed to precede type 2 diabetes by 10 to 15 years. In fact, insulin resistance is typically the first red flag of metabolic dysfunction. Insulin resistance—even in the absence of elevated fasting blood sugar—increases risk for health conditions. [3]
Let's discuss five ways in which insulin impacts healthspan.
Cardiovascular disease refers to a number of conditions related to the heart and blood vessels. Metabolic conditions like type 2 diabetes and obesity are risk factors for cardiovascular disease, but research shows there may be an association between high insulin levels in healthy people and the risk of cardiovascular disease—although more research is needed to draw a definite conclusion.
An older study from 2004 in over 11,000 individuals found that those with the highest levels of fasting insulin at the beginning of the study were significantly more likely to die from cardiovascular disease than those with the lowest insulin levels, regardless of other risk factors. [4]
However, a more recent 2017 review didn’t find that a person’s insulin levels alone were a risk factor for cardiovascular disease but that elevated insulin levels paired with other risk factors, like high cholesterol, were. [5]
When left unaddressed, insulin resistance can lead to prediabetes, and eventually type 2 diabetes. Even if other markers of metabolic health like cholesterol are normal, higher fasting insulin levels may lead to the development of metabolic syndrome. Identifying and addressing insulin resistance sooner rather than later can reduce the risk of developing type 2 diabetes.
Researchers of a 2011 study of 350 healthy Korean adults found that those who had the highest levels of fasting insulin at the start of the study had a five times greater risk of developing metabolic syndrome five years later. [6] Results of a 2018 study of Taiwanese adults without diabetes revealed that fasting insulin was linked to metabolic syndrome, even after considering other factors like age, weight, sex, and the presence of high cholesterol. [7]
Insulin resistance also contributes to weight gain and obesity. It hinders the body's ability to effectively utilize glucose for energy, causing cells to favor fat storage. This can make weight loss challenging for someone with insulin resistance, as the body holds onto energy rather than burning it. Some research also indicates that insulin resistance itself may be a predictor of weight gain. [8]
The brain is sensitive to insulin, but the effects of insulin on the brain are often overlooked. Cognition basically refers to functions that relate to the brain. This includes memory, reasoning, planning, problem-solving, and attention. Cognitive disorders—like Alzheimer’s disease and dementia—as well as cognitive decline are closely linked with aging. [9]
Persistently high levels of insulin can negatively impact memory and other cognitive functions and increase the risk of dementia. While more research is needed to fully understand the direct influence of insulin and overall brain health, improving insulin sensitivity is an attractive target for protecting against age-related cognitive decline. [10]
There is a well-established association between poor sleep quality and duration and a higher risk of developing diabetes. And the reverse is also true. Those who experience diabetes also reportedly experience poor sleep at a higher rate than nondiabetic individuals. [11, 12, 13]
Research shows that poor sleep contributes to insulin resistance. [14] Enhancing the quality of your sleep has the potential to positively influence your blood sugar levels and, consequently, insulin levels. Therefore, improving your overall metabolic health may have a beneficial impact on your sleep patterns.
Studies show that insulin resistance is associated with low serum testosterone levels in men. Researchers of a study published in Diabetes Care looked at the connection between sex hormones (testosterone, sex hormone binding globulin or SHBG), insulin, and body fat levels in 221 men without diabetes. Results showed that yes, higher insulin levels were accompanied by lower testosterone levels. However, body fat levels and SHBG levels may contribute to why we see this relationship. More research is needed to further understand this connection. [15]
Some symptoms of high insulin and blood sugar overlap with those of low testosterone including fatigue and weight gain. [16, 17] Determining your hormone levels through a blood test can help you identify the root cause of the physical symptoms you may be experiencing. Elevated hormone levels can inform your nutrition and lifestyle recommendations to alleviate physical symptoms.
It is clear that insulin resistance is closely correlated with numerous poor health outcomes—yet fasting insulin is hardly tested in routine blood screenings of healthy people. As insulin resistance is also one of the first indicators of metabolic dysfunction, this lack of testing means that many people are not aware of a problem until it arises.
InsideTracker now offers fasting insulin testing and analysis as a part of the Ultimate Plan (although it’s not available in Canada). Fasting insulin is tested alongside blood sugar markers like fasting glucose and hemoglobin A1c, among dozens of other healthspan-related biomarkers.
Depending on your biomarker levels and lifestyle habits, your Action Plan will include personalized lifestyle, nutrition, exercise, and supplements recommendations. The full analysis includes up to 48 blood biomarkers that offer insights into how your habits impact your levels, how biomarkers may impact one another, and what you can do to live healthier longer.
References:
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2901596/
[4] https://pubmed.ncbi.nlm.nih.gov/15241592/
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6448479/#
[6] https://cardiab.biomedcentral.com/articles/10.1186/1475-2840-10-108
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5942468/
[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3110645/
[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4402666/
[12] https://pubmed.ncbi.nlm.nih.gov/26131327/
[13] https://pubmed.ncbi.nlm.nih.gov/31546116/
[14] https://pubmed.ncbi.nlm.nih.gov/31546116/
[15] https://pubmed.ncbi.nlm.nih.gov/15047639/
[16] https://pubmed.ncbi.nlm.nih.gov/25879005/
[17] https://pubmed.ncbi.nlm.nih.gov/34203830/