Metabolic Flexibility
– The Way of Your Body –

Dr. Al Danenberg Nutritional Periodontist

October 25, 2020 [printfriendly]

I write and lecture about diet. The nutrients we consume must come from nutrient-dense, anti-inflammatory foods. I connect the medical dots relating to our way of eating, gut health, and immune system strength. Everything I discuss about diet, nutrition, and the immune system is critical for health. But it all comes down to one basic concept – metabolic flexibility.

Paul Saladino, MD has recorded many videos and interviews about the importance of metabolic flexibility for overall metabolic health HERE. And Travis Christofferson published his latest book titled, Ketones: The Fourth Fuel, which explains the essence of metabolic flexibility.


Factors of Metabolic Flexibility

Metabolic flexibility is the ability for our body to use carbohydrates and fats for fuel from a healthy diet.[1],[2] Nothing more; nothing less.

But of course, there are other factors than the foods we eat that affect metabolic flexibility. Some of them are efficient exercise, restorative sleep, and reduction of overall stress. Also, the frequency of eating is a big player. Intermittent fasting as well as multiday fasting improve metabolic flexibility as long as the food that is ingested is nutritious with no addition of irritants or chemicals.

That being said, a widely reported medical study was published on 9/22/20, which made two summary statements that I believe are misleading. The study evaluated a group of overweight and obese participants who only ate between the window of noon to 8 PM for 12 weeks compared to a control group who ate three meals a day with no time window. The authors observed that participants who did intermittent fasting statistically did not experience significantly more weight loss compared to the control group. In addition, the investigators pointed out that those who practiced intermittent fasting had a loss of muscle mass compared to the control group. Unfortunately, there was an important caveat that was not emphasized in the abstract although it was reported at the end of the paper. The caveat was that participants did not eat a nutrient-dense, anti-inflammatory diet, which I have stated is critical for intermittent fasting to be effective and healthy. In my opinion, this limitation makes the publication not relevant.

Another important factor of metabolic flexibility is a diverse and abundant gut microbiome. This is required for healthy digestion, proper absorption of nutrients, a robust immune system, and an intact gut epithelial barrier.

With all these vital factors in mind, let’s take a look at our primal ancestors for a broader perspective.


Carbs & Fats

Throughout our modern human evolution over the last 200,000 years, our body has been effective in using both carbohydrates and fats for fuel. Our human machine has the hormones and chemical pathways to tell fat cells to release their fat storage when the body needs fuel and is not consuming carbohydrates. In addition, our human machine has the hormones and chemical pathways to burn consumed carbohydrates as fuel when dietary fats are not available.

When insulin levels are turned on with carb consumption, our fat cells are turned off from breaking down their stored fat. In addition, insulin converts excess carbs into fatty acids and stores them as fat. As blood glucose levels drop, we get hungry again.

Unfortunately, if we are used to consuming an abundance of carbs, our body does not resort to burning fats when we get hungry. Instead, we develop cravings for more carbs! We are not metabolic flexible. We are not “fat adapted”. We are “carb addicted”.

Why do we crave carbs when we get hungry? If we are “carb addicted”, our body yearns for more carbs because they stimulate dopamine production in the brain. Dopamine gives us a “rush”. If you refrain from carbs at this time, you will experience “withdrawal” symptoms just as you would if you tried to withdraw from other addictive substances. So, you just keep eating more processed carbs.

Even worse, when we consume an abundance of fats along with an abundance of processed carbohydrates, the body will not burn the excess fats. The end result is that fats and excess carbs are stored as more fat. Also, the liver is compromised with excess carbs coursing through the circulatory system. Excess carbs in the liver can cause non-alcoholic fatty liver disease.

A vicious cycle ensues, where fat and glucose cannot be metabolized effectively.

As time goes on, and we eat an abundance of carbohydrates several times a day, day after day, our metabolic hormones become strained. Problems with sleep, exercise, stress reduction, and gut health also will affect glucose metabolism.


Development of Diabetes

Insulin levels work hard to store the excess carbohydrates as fat. But if overeating continues, the effects of insulin become compromised. The cells in our muscles, body fat, and liver start resisting or ignoring the signal that insulin is trying to send out. That important signal is to grab glucose out of the bloodstream and put it into our cells. This is called insulin resistance.

The pancreas compensates by producing even more insulin in order to create the same results that it provided before the continuous overloading of carbs. In time, the pancreas can’t produce enough insulin and blood glucose can’t be directed into the cells. We become prediabetic. If the condition worsens, we become a true diabetic because glucose is not being metabolized effectively. Ultimately, the pancreas could weaken to the point of shutting down its production of insulin.


Steps to Become Metabolically Flexible

So, how do we become metabolically flexible? We must address our sleep habits, exercise routine, and ability to deal with stress. It’s also critical we become fat adapted by eating nutrient-dense, anti-inflammatory foods. In addition, we have to maintain a healthy gut. And finally, we should investigate the benefits of fasting.

To become metabolic flexible, our body needs to relearn how to burn fat as fuel. To do this, we must eat a diet that is extremely low in carbs for at least 2-3 weeks. Sometimes it might take several months before our body adapts. Eventually, our liver will start producing ketones as a clean burning fuel as our metabolism shifts into ketosis. Usually, this requires us to consume less than 30 grams of carbs a day. Think about this: one large apple has 30 grams of carbohydrate – your maximum allotment for that day!

An ideal way of eating is to primarily consume animal-based foods from nose-to-tail. These will provide the necessary source of nutrients contained in the animal muscle meat, organs, collagenous parts, and their healthy saturated fats. The fat-to-protein ratio in terms of grams should be 2:1. Eating fats and proteins are satiating and will curb hunger. Animal foods are extremely low in carbs. In addition, a few plants that are low in phytates, lectins, and oxalates could be included as long as the total carbs are less than 30 grams.

As I stated, this eating lifestyle will put the body into ketosis, where fatty acids are being mobilized from fat cells to be used as fuel for the body, and the liver in now producing ketones as an additional clean-burning fuel. This is the protocol I describe in my Better Belly Blueprint.

After your healthy metabolic flexibility has been reestablished, you can cycle in and out of burning fat and burning carbohydrates. To do this, you could reduce your fat consumption once a week and eat about 100-150 grams of carbohydrates that one day. Your body will burn the carbs for fuel and store some of it in the liver and muscle as glycogen. Also, the release of insulin at that time will assist your body in various repair pathways that are required. Over the following 6 days, you can go back to a high fat and low carb way of eating. Your protein levels will remain moderate. And you will stay metabolically flexible.


My Personal Metabolic Cycling

First of all, MCT (medium chain triglycerides) Oil acts as an exogenous ketone source. When a person consumes it and is eating low carbs, the liver will immediately convert MCT Oil into ketones. The rush of ketones into the blood system will cross the blood brain barrier and will benefit cognition and neural tissues since it is a perfect brain fuel. It also decreases overall free radical creation, improves the production of ATP by mitochondria, and enhances the natural production of endogenous antioxidants. Basically, it extends ketosis and improves energy.

Now for my personal metabolic cycling regimen. I am not recommending the following regimen to anyone. This is for information only.

I eat an animal-based diet, which includes less than 10% plants as I described previously. In my morning coffee, I add MCT Oil. Starting at 6 AM, I blend 2 tablespoons of ghee and 2 tablespoons of MCT Oil in 16 ounces of pressed coffee. And I’ll drink this over the next couple of hours.

My ketone levels stay high. Then I continue my animal-based diet with my first main meal sometime between 2PM and 5PM.

I will cycle out of ketosis every 7th day by increasing my carbs to 100-150 grams and significantly reducing my fats that day. I get my carbs primarily from raw manuka honey, some bee bread, and occasional fruits. On “carb” day, I do not drink any coffee. This protocol keeps me metabolically flexible and boosts my overall wellbeing.

Be aware of this: It was critical for me to titrate up to my daily dose of 2 tablespoons of ghee and 2 tablespoons of MCT Oil per day. I started with 1 teaspoon daily until I finally reached 2 tablespoons. If I had jumped in with a total of 2 tablespoons of both the first day, I would have experienced nausea, stomach distress, and diarrhea.

Concluding comment: Our DNA blueprint wants us to be metabolically flexible. This is the way our body is supposed to work. This was how humans have survived and thrived throughout our evolution over the last 200,000 years.

One way to determine your metabolic flexibility is to understand how your body metabolizes ingested carbohydrates by measuring your glycemic variability (GV). You can do this 24/7 by using a Continuous Glucose Monitor (CGM). I describe the details in my personal experiment. Read the facts and how you can get a CGM to monitor your own GV HERE.

My bottom-line recommendation is: Don’t fool with Mother Nature!






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“Can I Cheat on My Paleo-type Diet?”

        Alvin H. Danenberg, DDS       September 11, 2015


evolution rI hope you haven’t reached the point where you discovered Paleo and were motivated to change your life and then thought, “Can I cheat on my Paleo-type diet?”


Removing unhealthy food choices and replacing them with healthy ones is a lifestyle change. It’s not a fad diet that comes to an end allowing you to return to old eating habits. As a matter of fact, if you only had eliminated the acellular carbs and foods that have a high carbohydrate density, you would have greatly reduced your food cravings, and your body would be healthier, and your mouth would be healthier. But, to answer the question, “Yes, you can cheat”.


Of course, you need to define what cheating means.


As Mark Sisson and Dr. Loren Cordain have stated in their writings, the 80/20-rule or the 85/15-rule work. That means, if you are eating the foods that are part of the nutrient-dense lifestyle 80-85% of the time, then 15-20% of the time you could go off track and still be OK. That off track time would be considered cheating or maybe just indulging off the grid.


I am motivated – perhaps beyond most people’s desire to be motivated. I am 68 years old as I write this. At this point in my lifestyle change, which only began in 2013, I am a fat burner. That means that I usually consume less than 150 grams of carbohydrates a day (without actually counting grams but by making healthier food choices), and for the most part I have no carb cravings. I can effectively burn stored fat for energy throughout the day. In addition, I generally skip a formal breakfast because I am not hungry and start my first meal after the noon hour and end my last meal of the day by 8PM (intermittent fasting). But, most people are not like me. I definitely get that.


Interestingly, there may be some actual benefits to cheating or indulging off the grid.


Break the Monotony


For some, it can be difficult staying the course of eating healthy. Sometimes that burger with all the dripping juices and perfect bun sounds awesome. Other times your buddies and you just are out and about, and a pizza with a beer would top off a perfect evening. So, you join them by indulging off the grid. That’s OK. It is a break from what may appear to you to be the monotony of sticking to a strict food regimen. Just don’t do it often. But for some people, especially those with autoimmune diseases, allergic reactions, and damaged guts, just an occasional indulgence could cause unpleasant and serious reactions. Personally, I do not cheat like this.


The Hormetic Effect


Hormesis is the term for generally favorable biological responses to low exposures to toxins and other stressors. That’s why plants build up phytonutrients in their cell structure to ward off potential pests and disease. The stress created externally will build strength internally. The plant becomes stronger and more resistant, and the human body can become stronger and more resistant. Some research (Here, Here, Here) has demonstrated that eating some bad foods at times might improve overall health. But, again, don’t make this a routine excuse because of some research to indulge off the grid.


Restart Your Metabolism


If you had reduced your carbohydrate intake significantly and for a prolonged time, you actually could have depressed your metabolic rate and stalled your weight loss. When you eat a big meal especially high in carbohydrates, you could trigger specific hormones to restart your weight loss goals.


My Personal Thoughts….


If you have been motivated to make a lifestyle change, then you probably are not thinking about actively cheating. You occasionally may want to eat foods that do not have the ideal nutrient density that you would otherwise eat, and that’s OK. You may go out with the guys or gals and decide you will indulge in a way that you normally would not do, and that’s OK. These are the exceptions and certainly not the rule. I can go to almost any restaurant, even fast-food types, and find something on the menu that I will eat. The important thing for me is this: I know what I won’t eat, and everything else is OK.


If you have started a healthier lifestyle, think about where you are now mentally and physically compared to where you were when you started. I am a perfect example of a person who has embraced a new lifestyle, which has changed my life. How could I ever consider going back to the way I was? How could I entertain the concept of cheating when I know that this Primal lifestyle has saved my life?


Best of luck pursuing your new lifestyle.