There are a lot of things that experts say are the "one thing" you need to do to maximize your longevity. My choice for that "one thing" is controlling insulin resistance. The goal should be to get insulin release from your pancreas to the lowest level to maintain good blood glucose control.
Let me explain why.
What is insulin?
Insulin is a hormone released by your pancreas in response to a change in your blood glucose. Your body likes to keep your blood glucose (commonly referred to, somewhat inaccurately, as your blood sugar) in a certain tolerance or range. That range is between 65-90 mg/dl. When your fasting blood glucose is checked by your doctor that is the number on which we are focused. When your fasting blood glucose consistently goes above 100 you are considered pre-diabetic and when over 125 you meet the criteria to be diagnosed with diabetes.
Your blood glucose rises in response to a meal, usually a meal more laden with carbohydrates, especially what are called "simple carbohydrates" like those with added sugars (8-11 tsp in your standard soda, for example), or refined grains like white flour or white rice. But all carbohydrates will increase your blood sugar as nutrients are moved into your bloodstream from your gut. Proteins can also raise your blood sugar but less so and fats least of all.
As this graph shows nicely:
As stated, this spike is most pronounced with simple carbohydrates and much flatter if taking complex carbohydrates or combining carbohydrates with protein or healthy fat.
As your blood glucose increases your pancreas starts to produce insulin. Insulin signals your body to start moving glucose out of your blood stream and into your muscles primarily. This becomes a more critical issue as we age since by the time we are 65 years old we have lost, on average, 25% of our muscle mass. This is due to hormone changes, but also we move less as we age, and this lack of movement accelerates the reduction in muscle mass. With less muscle, your body has a harder time "disposing" of increased glucose from your blood stream.
How insulin resistance happens
But where does the resistance come into play? Put simply, over time your pancreas has to push out more and more insulin to achieve the same level of glucose control. As that level rises over time the cells in the pancreas that produce insulin (called "islet cells") fatigue and wear out.
There are several reasons this happen, but the most common is a rising level of fat tissue stored in various places in your body. One of the places where fat tissue should NOT be stored are within the actual muscle cells. When this happens, typically due to increasing obesity, the fat accumulation inside the cells causes a mechanical block so the insulin can’t attach to the receptor on the muscle cell, which signals the cell to start taking up glucose.
To summarize: loss of muscle over time lessens your body's ability to regulate insulin. And too much fat tissue in the wrong place can cause the entire regulation of insulin to get blocked up.
Insulin and energy storage
Insulin also has another important function: telling your body to store energy.
In order to understand this we have to go back, way back like hundreds of thousands of years. From the time we walked upright until the last 75 years most human beings have been faced with one of two very different situations: times of feast and times of famine. As history has demonstrated, there have been many more famines than feasts. Your body, in a sense, is always worried metabolically that there will be a famine just around the corner.
The most efficient way for your body to store energy is in the form of fat, technically adipose tissue. As your insulin level rises, it signals your liver to store energy in the form of lipoproteins. These lipoproteins (LDL-low density lipoprotein, HDL-high density lipoprotein and, VLDL-very low density lipoprotein) are what are measured on standard cholesterol panels. They are the "carriers" of fat sent from your liver to long term storage in your adipose tissue.
Remember that over time your insulin level rises to overcome the block at the muscle cell to take up glucose. When someone has an elevated insulin level they are unable to break down stored fat because the message being sent to the liver is to store even more energy/fat. So, as you become insulin resistant you not only are burning out those cells in the pancreas, you are also unable to access and mobilize that stored fat as energy. It is a vicious cycle that leads to many unwanted consequences.
The connection to cardiovascular disease, cancer, and dementia
These consequences include the Big 3 of cardiovascular disease, cancer and dementia. Rising rates of insulin trigger an increase in lipoprotein production as stated above. This leads to not only more plaque being deposited into the walls of blood vessels but also accumulation in unwanted places like muscle cells and organs like your liver. This can contribute to non alcoholic fatty liver disease (NAFLD), now the most common chronic liver disease seen in up to 25% of adults in the US—it is also completely reversible if appropriate steps are taken.
More adipose tissue leads your body to send out more inflammatory mediators. These are a class of molecules called cytokines made famous by the "cytokine storm" we heard about in severe infections like sepsis and COVID. This increased inflammation makes the plaque deposits in arterial walls worse, accelerating cardiovascular disease leading to heart attacks and strokes. It also is a contributor to rising rates of certain cancers.
Cancer is a complex disease with numerous genetic markers that can increase or decrease your risk. But the link to insulin resistance is focused on those inflammatory mediators (cytokines) which can influence how cells grow. Insulin is pro-growth, stimulating cells to continue to grow. This increases the risk of abnormal cells continuing to grow instead of the normal process of cell death once past their normal life expectancy. Long-term increased insulin raises your risk for breast, prostate or colorectal cancer.
Dementia rates also increase as your blood sugar increases. People with Type 2 diabetes have 1.6x times the risk of dementia compared to non-diabetics. The theory is that increased insulin influences how beta amyloid proteins are cleared from the brain. Rising rates of insulin also impact blood flow in the brain similar to that of cardiovascular disease through plaque deposition and increased inflammation.
While that all sounds terrible, and it is, there is a way to partially or completely reverse all these trends. It depends on where you are on the curve of "burning out" those insulin producing cells in your pancreas.
Reversing insulin resistance
The first step is to eliminate, as much as possible, any foods which will cause a spike in your blood glucose and insulin level.
The following can cause a person’s blood sugar and insulin levels to spike:
sugary drinks, such as soda, juices, and sports drinks
processed foods and baked goods, which often contain trans fats
white rice, bread, and pasta
breakfast cereals with added sugar
yogurts with added sugar
honey and maple syrup
flavored, sugary coffee drinks
French fries
Another important aspect of reversing insulin resistance is to limit saturated fat intake. What about all those proponents of keto and paleo diets, you might say? Here is the issue. An increase in free fatty acids, which are breakdown products of saturated fats, trigger more production of those lipoproteins mentioned above, resulting in more deposition of adipose tissue and in places you do not want it deposited, like your muscles or liver.
Additionally, you need a way to mobilize that stored energy and make it usable calories. That is where movement comes into the plan. Your focus should be on Zone 2 activity where you are moving at a controlled pace allowing your body to continue to burn ketones as fuel and not glucose. This is a much lower intensity of movement where your heart rate is elevated but you are still able to carry on a conversation. The best example is walking at a brisk pace. Depending on your level of fitness, this may be a 15-to-20-minute mile pace. Low and slow is the key. You need to maintain this activity for at least 30-40 minutes continuously to get the maximum benefit.
To summarize: the path toward reversing insulin resistance involves focusing on a plant based nutritional regimen, minimizing saturated fats and using Zone 2 activity to mobilize stored energy and fat stores. With this reversal, you will see improvements in metabolic health markers and dramatic reductions in chronic diseases like cardiovascular disease, diabetes, cancer and dementia.
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