While we often think of flexibility in terms of stretching, metabolic flexibility is a different and more important aspect of optimal health.

Metabolic flexibility refers to the ability of your mitochondria to flux between burning ketones from fat and glucose from carbohydrates.  This makes sense when you consider that for the majority of human evolution, there have been times of feast and famine. For instance, a tribe may have feasted after a successful hunting trip or the occasional bounty of honey found in a beehive, but then go weeks only eating small amounts of wild plants.  In this case, their bodies would have to be able to utilize the large amount of fuel from food and then rely on fat stores to maintain energy between large meals.

Too much feasting, too little fasting

For most people today, there is a little too much feasting and not enough fasting. Fasting is an important health-promoting part of our metabolic rhythm. Too much food too often is a driving force behind the trend in chronic diseases such as obesity, cardiovascular disease, cancer, autoimmunity and other chronic disease. 

In fact, the effectiveness and popularity of intermittent fasting and time restricted eating is largely due to our body’s desire to fast. When we abstain from food for 16-24 hours or more, we induce a state of “famine” which forces our bodies to burn stored glucose and then begin to burn stored fat.  These popular practices mirror the feast-famine rhythm our ancestors adapted to.

Fueling your body

Fuel is generated from the building blocks of carbs and fat.  Foods like grains, beans, lentils, root vegetables, and sweets require digestion to break carbs down into little glucose molecules.  Once that happens, glucose moves across the intestinal lining into the bloodstream. At this moment, the pancreas is triggered to release insulin from pancreatic beta cells. Insulin moves into the bloodstream alongside glucose where it’s delivered to cells where it docks on healthy insulin receptors like a perfectly fitting puzzle piece.  

If this metabolic process malfunctions, due to damaged insulin receptors or an injured pancreas, glucose metabolism is stunted. But glucose isn’t a cell’s only option for fuel.  If your body loses its ability to burn glucose, you can train it to burn ketones instead.  

Side-note: while Americans love their protein shakes, protein is not a fuel source for your cells. Only fat and carbohydrates can be used for cellular energy production.  Protein breaks down to amino acids that then must be converted to glucose via gluconeogenesis (gluco=glucose neo=new genesis=creation). Keto dieters might experience this when a meal that is too high in protein results in high blood sugar and an end to ketosis.

Your body’s reliance on carbs for fuel is the reason that overfeeding, or eating too much food throughout the day leads to dysfunctional metabolism and eventually insulin resistance. Too much food too often stresses the body and results in inflammation.  Inflammation (the immune system’s response to a threat, even when that threat is too much food) causes injury to insulin receptors on the surface of our cells. If insulin receptors are damaged, they don’t recognize insulin and that prevents glucose from entering the cell where it should be metabolized into energy.  In essence, this means glucose remains in the bloodstream, spiking blood sugar and starving cells of their much-needed fuel source. The result is a body that is fatigued, inflamed, overweight and headed towards disease.

This damaging process can progress silently for years or decades before becoming severe enough to identify as diabetes. I see dozens of clients each month that are in the early phases of this process, unknowingly experiencing blood sugar spikes every day while their bodies can’t keep up with the influx of carbohydrates that break down into glucose in the bloodstream.

Maximizing your metabolism

The solution to this vicious cycle of poor metabolic flexibility is giving your body a chance to “starve” from glucose so its forced to use fat for fuel.  There are a few ways to accomplish this.  

 

1. Intermittent fasting

Intermittent fasting, an approach that reduces caloric intake to 500-800 calories depending on metabolic needs can be practice 1 -3 days per week.  Decreasing intake intermittently can create a rhythm similar to what our ancestors may have undergone. While our nomadic predecessors may have feasted after a successful hunt, they were often relegated to foraging for low-calorie plants.  This rhythm naturally moves the body between feasting and fasting, first burning through glucose stored as glycogen in the liver and muscle cells and then shifting to burning ketones derived from fat stores. 

1. Time restricted eating

Time restricted eating, often confused with intermittent fasting, controls eating within an 8 hours period per 24 hour cycle.  This means that if your first meal is at 8 a.m., your last meal is over by 4 p.m. You can create any 8 hour framework for eating, but it’s important to stop eating at least 4 hours before bed to maximize metabolism.  

Warning that people who are currently experiencing poor blood sugar control, hormone or metabolic imbalances will struggle to manage their energy needs with this approach.  However, many people find great success with time restricted eating and find it really accessible. In fact, research reveals that when people eat within an 8-hour period instead of a 12-16 hour period, metabolism and disease risk factors improve significantly.

1. Low-carb diet

Eating low-carb means restricting calories from carbs to somewhere around 50-100 grams of carbs per day instead of the typical 250-400 grams that most people eat.  This type of diet still provides some carbs but doesn’t overwhelm the body with sugars it can’t metabolize.  

By identifying how many carbohydrates your body burns, you can prevent blood sugar spikes, improve insulin sensitivity and boosting cellular metabolism.  A healthy low-carb diet typically reduces or totally removes grains, sweeteners like maple syrup or honey and legumes like peas, lentils and beans while filling up on good-quality nuts, seeds, avocado, coconut, healthy oils, low-carb veggies, berries, and small amounts of meat, eggs, fish, and poultry. 

1. Alternating low and high carb

If you already have healthy glucose metabolism, you can boost your metabolic flexibility by rotating between low-carb or mild ketogenic periods and phases that provide a much higher carbohydrate intake.  This trains the body to flux between relying on fat and handling large flushes of glucose. When my clients are interested in this approach, we make sure to test blood sugar on the higher carb days to insure that they are not getting excessive blood sugar spikes that can lead to damage and disease.  In the right situation, this can really boost metabolic flexibility.

 

1. Fasting mimicking diet

Dr. Valter Longo, head of USC’s department of longevity has studied the benefits of fasting for decades.  From this research, he developed a diet that mimics the rewards of water fasting without having to go through the struggle of refraining from food for 5 days.  His 5-day fasting mimicking diet, Prolon, provides a perfectly composed vegan diet that systematically restricts calories. This eases the body into a fasted state resulting in reduced inflammation, weight loss, better glucose and cholesterol control, significantly increased stem cell production and autophagy (clean-up and removal of aging and unhealthy cells). 

Many of my clients use this program once a month or once a quarter to reset their body and boost metabolism.  This program isn’t right for everyone but is an effective tool for most people.  

Boost your metabolic flexibility now

Wondering what approach is right for you?  This is where the experimenting begins. Designing your optimal nutrition approach is all about trial and error and learning to listen to your body.  To begin experimenting with the best approach, follow this step-by-step plan:

Step 1

Cut all junk food and eat whole foods only

Step 2

Start testing your blood sugar (click here for your glucose testing guide)

Step 3

Now that you’re eating whole foods, reduce your carbohydrate intake by restricting sugar in any form, and cutting your grain and legume intake in half.  If your blood sugar is remaining in optimal ranges, try a high carb day and track your blood sugar)

Step 4

If your blood sugar is still elevated between or after meals, reduce carbs by removing grain, legumes, high carb fruits and veggies. Click here for a guide to increasing fat and decreasing carbs.

Step 5

Once you find the meals and foods that stabilize your blood sugar, try out time restricted eating and confirm that your blood sugar stays balanced.

Step 6

From here you can play with intermittent fasting, time restricted eating and high-carb feedings.  As long as your blood sugar remains in healthy ranges, you are on your way to metabolic flexibility.  You should see your body composition respond while getting a big boost in energy and sleep quality.

 

Dialing in your blood sugar and still not getting the results you want?  See my post on food sensitivities and blood sugar control. If you aren’t getting the results you need, it’s time to explore the next level of your optimal nutrition!