Your body showcases incredible adaptability, particularly on a cellular level. While it may not exhibit flexibility in the classical sense—like reaching your toes—its metabolic flexibility allows it to utilize various macronutrients, including carbohydrates and fats, as energy sources.
This capability was crucial for early humans facing erratic food availability, and it retains its importance today. However, the convenience of calorie-dense processed foods can hinder this metabolic adaptability and lead to health complications.
Understanding Metabolic Flexibility
Metabolic flexibility refers to the body’s capacity to transition seamlessly between various energy sources depending on food availability and activity levels.
Glucose serves as the primary energy source, a straightforward carbohydrate present in items such as sugar, candy, and refined bread. The body converts complex carbohydrates from grains, vegetables, and other foods into glucose.
Following a meal, glucose is typically utilized first, with any surplus stored as glycogen and fatty acids. Kim Shapira MS, RD, a nutrition therapist and the author of This Is What You’re Really Hungry For: Six Simple Rules to Transform Your Relationship with Food to Become Your Healthiest (BenBella, 2023), notes, “When we eat beyond hunger and lack the capacity in our muscles to store excess fuel as glycogen, we convert that energy into fat.”
In times of prolonged fasting, the body shifts its energy use to glycogen and fatty acids. During physical activity, it draws on glucose as well as stored glycogen and fatty acids.
Advantages of Metabolic Flexibility
One key advantage of metabolic flexibility is the body’s capacity to adapt to varying energy requirements throughout the day, even after a period of fasting. Early research indicates that greater metabolic flexibility is linked to effective weight management, a decreased likelihood of metabolic syndrome, and more stable blood glucose levels.
Metabolic syndrome encompasses a group of conditions that elevate the risk of heart disease, diabetes, stroke, and various other health issues. A diagnosis of metabolic syndrome occurs when an individual presents three or more of the following risk factors:
- elevated blood glucose
- low HDL (“good”) cholesterol levels
- high triglyceride levels
- an increased waist circumference
- elevated blood pressure
Conversely, reduced metabolic flexibility is often linked to insulin resistance, which contributes to type 2 diabetes, obesity, cardiovascular diseases, and additional health complications.
Insulin resistance occurs when cells in muscles, fat, and liver fail to respond adequately to insulin, the hormone that prompts cells to absorb glucose for energy, ultimately increasing blood sugar levels. Consequently, blood sugar levels remain elevated, cells generate less energy, and the pancreas compensates by producing more insulin.
Metabolic Flexibility and Metabolism: What’s the Difference?
Metabolism encompasses all chemical processes in the body that generate energy necessary for daily operations, including nerve and muscle activation and tissue formation. Metabolic flexibility is merely one element of metabolism, indicating the ability to alternate between energy sources.
The amount of energy required by your body while at rest is referred to as the basal or resting metabolic rate. Factors influencing this rate include sex, weight, height, age, ethnicity, body composition, and genetics.
Of these variables, only weight and body composition are subject to change. Increasing muscle mass through strength training is one method to enhance your basal metabolic rate, while weight loss via exercise and dietary modifications is another. However, each approach may not guarantee immediate metabolic adjustments.
Enhancing Metabolic Flexibility
To support and improve metabolic flexibility, consider these strategies:
Prioritize a whole-food diet with minimal processed foods and added sugars. “Every individual should incorporate a variety of fermented foods, fruits, vegetables, whole grains, fiber, and quality probiotics,” advises Shapira.
Avoid excessive caloric intake, particularly eating when not hungry, which may contribute to insulin resistance irrespective of weight. Shapira emphasizes the importance of being in tune with hunger cues, stating, “Hunger signifies that our body is metabolically active and functioning correctly. However, overeating or undereating disrupts this balance.”
Maintain physical activity, which can enhance metabolic flexibility and insulin sensitivity. Shapira claims, “To achieve a healthy weight, aim for at least 10,000 steps daily or engage in an active lifestyle, incorporating diverse movements like strength training, cardiovascular fitness, flexibility, and endurance.”
Improve sleep quality. Insufficient sleep can lead to increased insulin resistance and inflammation. “If you struggle with falling asleep, staying asleep, or wake up unrefreshed, stress is likely contributing to inflammation,” warns Shapira.
Effectively manage stress. While physical exercise can help mitigate stress, Shapira cautions that those experiencing chronic stress should opt for gentler activities, like moderate walking, yoga, or Pilates. “Intense workouts may escalate stress levels and hinder sleep,” she states.
This piece was first published in the May 2025 edition of Intomodel magazine.
