How To Build ‘Metabolic Flexibility’ For Energy And Fat Burning

Have you ever wondered why some people can skip a meal without crashing, go from high-carb days to low-carb days without energy dips, or power through workouts without needing a constant snack supply? Chances are, they’re metabolically flexible.

According to an article published in Endocrine Reviews, “metabolic flexibility is essential to maintain energy homeostasis in times of either caloric excess or caloric restriction, and in times of either low or high energy demand, such as during exercise.” 

Unfortunately, most people today are metabolically inflexible and locked into carb-dependency due to constant snacking, refined foods, and disrupted circadian rhythms. This leaves many folks with low energy, as well as frequent blood sugar crashes, cravings, and stubborn fat stores.

Ahead, learn more about metabolic flexibility, plus tips for building it.

• ABOUT OUR EXPERTS: Lena Bakovic, R.D.N., is a registered dietitian with Live It Up. Karen Linardakis-Cooney, B.C.H.H.P., C.N., is a board-certified holistic health practitioner and nutritionist with The Vitamin Shoppe.

Intro to Metabolic Flexibility

Metabolic flexibility is your body’s ability to seamlessly switch between using carbohydrates and fat for fuel. In other words, it’s a sign that you can efficiently use both glucose and fatty acids—and even ketones when needed—for energy without experiencing negative effects, says Bakovic.

“Metabolic flexibility is also indicative of how our bodies respond to periods of fasting, varied dietary patterns and food sources, and different forms of exercise,” she explains.

The Benefits of Being Metabolically Flexible

Improving metabolic flexibility can support many areas of health, according to Lena Bakovic, R.D.N., a registered dietitian with Live It Up. A few of its biggest impacts:

• Balanced energy: As your body becomes more equipped to run off different energy sources, you can say goodbye to intense blood sugar crashes and afternoon slumps.
• Improved fat burning: Your body becomes more efficient at using stored body fat for energy, which can help you maintain a healthier weight and body composition.
• Better blood sugar control: Metabolic inflexibility can contribute to insulin resistance, which can then set the stage for type 2 diabetes and other related health issues, such as a higher risk for cardiovascular and metabolic disease. Maintaining healthy insulin function means more stable blood sugar—good news for energy and long-term health.
• Increased workout performance: Metabolic flexibility may improve mitochondrial health, which is vital for energy production within the cells.

Health pioneers like Mark Sisson have been waving the metabolic flexibility flag for years. But now, the term is gaining traction among athletes, biohackers, and everyday wellness seekers alike. 

Why? Metabolic flexibility isn’t just beneficial for burning fat or going low-carb without feeling wiped out. It’s about adaptability and teaching your body how to efficiently switch between energy sources (carbohydrates and fats) as needed.

How To Build Metabolic Flexibility

Like a muscle, your metabolism needs training to stay strong. Here’s how to start flexing.

1. Practice Intermittent Fasting 

Fasting gives your body a break from digesting glucose and encourages fat adaptation. Even short daily fasts (such as 12 to 16 hours, including overnight) can help train your metabolism to burn fat more efficiently. 

“Incorporating intermittent fasting, or time-restricted eating, can help your body learn to use different energy sources more effectively,” suggests Bakovic.

Many experts recommend starting intermittent fasting gently by skipping food for 12 hours overnight (think 7 p.m. to 7 a.m.). Gradually, you can increase your fast to 14 to 16 hours (or longer) as tolerated. Avoid high-carb binges post-fast to support fat burning, and instead focus on whole foods and balanced meals that contain protein, healthy fats, and fiber.

2. Train in a Fasted State

Exercising before you eat in the morning encourages your body to tap into fat stores for fuel. This can help enhance fat oxidation and build metabolic resilience, explains Bakovic. “Specifically, doing some type of endurance exercise training can help optimize mitochondrial function and allow your body to utilize different fuel and food sources,” she notes.

Try light-to-moderate cardio (like walking or Zone 2 training) in the morning before breakfast. Limit this to two to three times per week if you’re new to fasted training, adds Bakovic.  

As long as you don’t feel lightheaded or weak, continue doing this regularly if it works well for you. If you train intensely and find that eating before workouts helps your performance, you can skip this strategy and focus on other habits, she says.

3. Cycle Carbs Strategically

Alternating between low-carb and moderate- or high-carb days can teach your body to handle both fuel types while also assisting in weight loss, research suggests. “Strategically having times of lower-carbohydrate intake can help one’s body optimize fat-burning,” says Bakovic.

She recommends adjusting your carbohydrate intake based on your workout routine. “Plan high-carbohydrate intake days around more intense training, as it helps to build up glycogen, or stored energy that supports tougher efforts,” she says. On these days, go for high-fiber carb sources, such as sweet potatoes, fruit, or quinoa, to help your muscles perform and recover. “Then, stick to low-carbohydrate intake for lighter training days,” Bakovic says.

Read More: 7 Ways To Make Your Carb Consumption More Blood Sugar Friendly

For best results here, lower your carb intake gradually. “A low-carb day should be low-carb, not no-carb,” suggests Karen Linardakis-Cooney, B.C.H.H.P., C.N., a board-certified holistic health practitioner and nutritionist with The Vitamin Shoppe. Instead of dropping from 200 grams of carbs to 30 grams overnight, taking a more moderate approach (think 200 grams to 100 grams) allows the metabolism to adapt more smoothly, she says.

4. Prioritize Whole Foods, Protein, and Quality Fats

If greater metabolic flexibility is your goal, start here: “Consume a dietary pattern primarily consisting of whole foods, and limit foods that have undergone processing,” says Bakovic. “This is beneficial for both metabolic and general health.” 

Once you’ve got that down, make sure you’re consuming enough protein and healthy fats. “Protein stabilizes blood sugar and prevents muscle breakdown,” says Cooney. It also supports satiety, so you’re not reaching for sweet snacks every 30 minutes. Meanwhile, healthy fats encourage ketone production (which occurs when the body breaks down fat for fuel), adds Bakovic. 

Cooney recommends aiming for 0.7 to one gram of protein per pound of body weight daily. If you weigh 180 pounds, that’s 126 to 180 grams of protein each day. Meanwhile, you can get the healthy fats you need by including avocado, grass-fed butter, egg yolks, fatty fish, olive oil, and coconut oil in your daily eats, she says. Just steer clear of the highly processed oils found in many packaged foods.

5. Increase Your Water and Electrolyte Intake

On lower-carb days, electrolytes are a must, according to Cooney. “Electrolytes like sodium, potassium, and magnesium are lost more rapidly when eating low-carb due to increased urination.” In some cases, loss of electrolytes can lead to weakness, fatigue, and dizziness.

Luckily, staying stocked on these minerals isn’t too tough. “You can replenish electrolytes with bone broth, electrolyte powders, or mineral-rich foods, which include seaweed, leafy greens, dairy products, nuts, seeds, and avocados,” says Cooney. Of course, make sure you’re drinking enough water (experts often recommend half your body weight in ounces of H2O) alongside these sources.

6. Sleep Like It Matters (Because It Does)

Poor sleep can wreck blood sugar regulation and increase carb cravings the next day, making you more prone to overeating not-so-nutritious foods. For example, one study states, “neurologically, compared to a sleep-rested state, sleep deprivation diminishes activity in areas of the brain associated with food choice (hypothetically leading to poor choices), and amplifies activity in an area known to signal food salience and promote eating.”

Read More: 8 Steps To Bouncing Back From An Awful Night Of Sleep

According to the Sleep Foundation, adults should aim for seven to nine hours of quality sleep per night. If you struggle to sleep well, be sure to avoid screens and bright lights one to two hours before bed to support melatonin production, and make sure to keep your bedroom dark and cool.

Keep a consistent bedtime, even on weekends. Other habits that can help include getting sunlight exposure during the day, exercising, and doing relaxing activities at night, such as reading, meditating, or journaling.

7. Use Mitochondrial-Supporting Supplements

Your mitochondria (the “energy factories” of your cells) are the engines of metabolic flexibility. They determine how efficiently your body converts energy from food and fat stores into energy your cells can use. When your mitochondria are functioning well, they can adapt quickly to shifts in fuel sources, helping maintain steady energy levels, even during fasting or low-carb eating.

You can help support them with:

• Berberine or berberine plus chromium to help improve insulin sensitivity and glucose control
• ALA (alpha-lipoic acid) for supporting glucose metabolism
• Magnesium for supporting energy metabolism and ATP production
• Exogenous ketones or MCT oil to kickstart fat-burning pathways when carbs are low

8. Limit Snacking And Grazing

Constant food intake trains your body to rely solely on glucose for energy, preventing it from ever tapping into fat stores, says Bakovic. That’s why both she and Cooney stress the importance of avoiding “mindless” snacks between meals, especially on packaged goods and sweets.

Instead, stick to two to four solid meals a day, and be sure that each meal includes some mix of protein, fiber, and healthy fats to keep you full, Bakovic recommends. “This can help our bodies boost fat burning and learn to use different energy sources more effectively,” she says.

Try drinking water, herbal teas, or electrolytes during those in-between windows to curb your appetite as you adjust to this new eating pattern.