Insulin resistance, Insulin sensitivity, metabolic fitness...

Insulin resistance, insulin sensitivity, metabolic fitness, time restricted feeding, continuous glucose monitoring.. what does it all mean?

Insulin resistance is the body’s response to too much insulin. When insulin levels are high, the body develops a resistance to it. Excessive insulin causes obesity because insulin is a fat storage hormone. And excess insulin causes insulin resistance, also called type 2 diabetes. So why would we treat a disease of excess insulin with more insulin? Good question. To be clear, I am not talking about Type 1 diabetes, which is marked by a lack of the ability to produce insulin and those patients have to have externally administered insulin. Type 1 is a totally different disease process.

Insulin is produced by the pancreas in response to ingested food. Different food stimulates a higher or lower insulin response. Insulin’s job is to take glucose from your bloodstream, (aka sugar from carbohydrates that you ingest) and move it into your cells for energy. Insulin resistance keeps your cells from responding to insulin so the glucose in your blood can’t enter your cells and it builds up in your bloodstream causing high blood sugar readings. Then the body produces more insulin to try to push more glucose into the cells. So insulin levels in your blood are high, and blood sugar is high and this keeps you from burning fat for fuel, because insulin is a fat storage hormone. The answer then is to reduce insulin levels to restore the insulin sensitivity in your cells. So how do you do that? That is where fasting can be helpful. Dr. Jason Fung wrote a book called “The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day and Extended Fasting.” He discusses the different ways of using fasting and the metabolic benefits to restore insulin sensitivity.

Does all food affect insulin production in the same way or to the same degree? The three macronutrient categories are protein, carbohydrates and fat. Insulin production is most stimulated by carbohydrates, especially refined carbs like sugar. Protein and fat can stimulate insulin as well but to a lesser degree. It is also interesting that different people respond differently to different foods. I’m not sure we really know why, but most likely a combination of genetics, metabolic and hormonal differences and level of physical activity.

So to decrease insulin production, you need to stop stimulating it with food, which is where the fasting comes into play. As mentioned before, there are many forms of fasting, from a 5 day water only fast to alternate day fasting or time restricted feeding. I am most familiar with time restricted feeding, also sometimes called intermittent fasting, because that is what I have practiced most often. One common method is called 16:8 time restricted feeding. That means you fast for 16 hours and eat during an 8 hour window. One way to do this is to not eat your first food until 10am, eat your last food at 6pm (8 hour feeding window) then fast from 6pm until 10am the next morning. (16 hour fast) You can also eat earlier if breakfast is important to you so you could eat from 8am to 4pm for example, then fast again overnight.There is some evidence that eating earlier in the day has metabolic benefits. There is obviously controversy about what types of food are best- ketogenic, carnivore, vegan, pegan, etc, but that is a whole other discussion! All those plans still agree on cutting out sugar and refined carbohydrates if you are trying to improve insulin sensitivity and metabolic fitness.

Many of us may resist the idea of going without food for 16 hours since we are a culture of abundant food that is always available. Do I get hungry? Yes I do! I am a chronic snacker, so it takes effort to resist that and not have tempting foods available. My fasting blood sugars have been in the pre-diabetic range for a while and I have seen improvement with a lower carb, higher protein approach with time restricted feeding. I am not perfectly compliant, especially while traveling and staying with friends and family along the road. But I am making progress! And I also found that I can learn to be comfortable with mild hunger and not feel like I have to feed it constantly.

One of the challenges with monitoring your blood sugar is that it has required a finger stick to check your glucose levels. Typically people check first thing in the morning while fasting to measure fasting blood sugar levels. The optimal level is between 72-85mg/dl. But what does that really mean if you are only checking your blood sugar occasionally and you aren’t measuring blood sugar after eating to see how your body responds to different foods? Now we have something called a continuous glucose monitor (CGM) that is applied to your skin on the back of your arm with a tiny hair like filament that enters your skin and measures your glucose continuously! There is then an app on your phone that can scan the monitor and give you a readout of what your blood sugar is doing. People using this device have found that certain food spikes their blood sugar more than they would have expected and it is different for different people. Like so much in medicine, there are individual difference.

The ultimate goal is to develop metabolic fitness. What does that mean? From the blog on the Levels Health web site: “We take “metabolic fitness” to mean our ability to keep average and fasting glucose levels in an optimal range, minimize post-meal glucose spikes, optimize insulin sensitivity, and to exhibit flexibility in utilizing different energy sources — including stored fat and glucose — for fuel.” https://www.levelshealth.com

It is how well we process energy in the body.

From the Levels Health website- the position of the CGM on back of arm

The good news is that we can make changes in our diet and lifestyle that will improve insulin sensitivity and metabolic fitness. You want to choose food that does not cause large spikes in glucose, exercise consistently, get quality restorative sleep, manage stress and avoid environmental toxins.I know, easier said than done! But when your metabolic fitness is poor, you are more prone to diminished brain function, low energy levels, poor memory, depressed mood, and risk for multiple chronic diseases. Having a continuous glucose monitor gives you information about how your particular body and metabolism responds to the foods you eat and the exercise you do. It is hard to change a behavior if you don’t know what is contributing to the problem.

Levels Health is a company that has developed an app and software that pairs with a continuous glucose monitor made by Abbott called FreeStyle Libre. The app gives you a direct view how your food and lifestyle affect your blood sugar so you can make changes that are specific to your metabolism. The FreeStyle Libre is available by prescription through your medical provider, but is typically used for people with a diabetes diagnosis. It may or may not be covered by Medicare, but last time I checked my plan it was not covered. The advantage of Levels is that it is available to a broader group of patients, including those who want to optimize their metabolic fitness even if they do not have a diabetes diagnosis. I went to their website, entered my information as requested and then it was reviewed by a physician in the state where I live to provide approval. The monitor is on it’s way so I have not yet used it, but I will post about my experiences in my next blog.

The cost from Levels was $399. This may be an introductory offer, so I’m not sure how long it will be offered at this price. It includes 28 days worth of monitoring and then you would need to purchase more monitors. A 14 day Freestyle Libre kit from Abbott costs $85-$100 depending on where it is purchased and does not include the Levels Health software analysis.

I realize that I am just scratching the surface of this topic. There is much more that could be said and for a more in depth discussion I highly recommend the blog posts on the Levels Health website as well as books by Jason Fung, MD about fasting and obesity. Our metabolic health is super important as we realize that the severity of Covid 19 has been correlated with poor metabolic fitness in many cases. Stay tuned for my next blog when I have had a chance to experiment with my CGM! Stay well!

Resources:

https://www.levelshealth.com

The Complete Guide to Fasting by Jason Fung, MD

The Obesity Code by Jason Fung, MD