By Dr. Steven Long, DO, MHA, CPT
Beyond Health | Precision Medicine for High-Performance Living
Most people think of metabolism as a single “speed”—a number that determines whether they gain or lose weight. In reality, metabolism is a dynamic system made up of multiple moving parts: basal energy needs, activity, movement, and the cost of digesting food itself.
Understanding how energy is used and stored allows us to move beyond calorie myths and into true metabolic health optimization.
1. Key Metabolic Terms Defined
Basal Metabolic Rate (BMR)
The basal metabolic rate is the amount of energy (calories) your body requires to sustain vital functions at rest—heart beating, breathing, brain function, temperature regulation, and cell maintenance.
It accounts for roughly 60–70% of total daily energy expenditure (TDEE) in most people (McClave & Snider, J Parenter Enteral Nutr, 2001).
BMR is largely determined by:
Even small changes in lean mass can meaningfully affect BMR—one reason resistance training and adequate protein are so vital for long-term weight management.
Total Daily Energy Expenditure (TDEE)
Your TDEE represents the total calories burned in a day and is the sum of four main components:
Non-Exercise Activity Thermogenesis (NEAT)
NEAT refers to all the spontaneous movement you do outside of formal exercise: walking, fidgeting, standing, cooking, gardening.
It varies tremendously between individuals—sometimes by as much as 1,000–2,000 calories per day (Levine, Am J Clin Nutr, 2002).
When we diet or become sedentary, NEAT often drops subconsciously, slowing weight loss even if calorie intake is unchanged.
Preserving NEAT—through standing, walking, and general movement—is critical for maintaining energy balance and metabolic health.
Activity Energy Expenditure (AEE)
AEE refers to the calories burned through intentional exercise—running, lifting weights, cycling, etc.
While AEE typically represents only 10–20% of total energy expenditure, it has disproportionate benefits for cardiovascular fitness, muscle preservation, insulin sensitivity, and longevity.
Anabolism and Catabolism
Anabolism is the process of building or synthesizing tissues—muscle growth, repair, glycogen storage, and bone remodeling.
Catabolism is the breakdown of tissue or molecules to release energy—muscle breakdown, fat oxidation, glycogen use.
A healthy metabolism maintains a dynamic balance between anabolism and catabolism.
Chronically catabolic states (from under-eating, illness, or inactivity) lead to muscle loss, lower BMR, and frailty.
2. Thermic Effect of Food (TEF): Why All Calories Aren’t Equal
Every time you eat, your body expends energy to digest, absorb, and metabolize nutrients. This is the Thermic Effect of Food (TEF)—the energy cost of processing what you eat.
Average TEF Contribution
TEF accounts for roughly 10% of total daily energy expenditure, but it varies greatly depending on macronutrient composition (Westerterp, Physiol Behav, 2004).
Macronutrient | Thermic Effect (% of Calories) | Explanation |
Protein | 20–30% | High enzymatic cost to break peptide bonds and synthesize new proteins |
Carbohydrates | 5–10% | Requires energy for glycolysis, glycogenesis |
Fat | 0–3% | Easily stored with minimal metabolic conversion |
Mixed Diet | ~10% | Varies with composition and fiber content |
In other words, 100 calories of protein might yield only ~70 usable calories, while 100 calories of fat yields ~97.
This difference, while modest daily, can add up significantly over time and helps explain why high-protein diets support weight management and lean mass preservation.
3. Why Protein Matters for Metabolic Health
Protein’s high thermic cost, combined with its anabolic role in maintaining muscle, makes it a cornerstone of long-term weight regulation.
Adequate protein intake:
Studies show diets higher in protein (≥1.2–1.6 g/kg/day) preserve muscle mass during calorie restriction and prevent the drop in resting metabolism often seen during dieting (Leidy et al., Am J Clin Nutr, 2015).
4. Carbohydrates, Fat, and Energy Efficiency
Carbohydrates
Carbs have a moderate thermic effect (5–10%), meaning they’re moderately energy-intensive to process.
They are stored as glycogen in muscle and liver, and excess is converted to fat through de novo lipogenesis—a metabolically inefficient but rare pathway in healthy individuals.
Carbohydrates fuel higher-intensity activity, support thyroid function, and help preserve lean mass when paired with resistance training.
Fat
Fat is the most energy-dense macronutrient (9 kcal/g) and has the lowest thermic cost (0–3%).
Its storage is metabolically efficient—nearly direct from dietary triglyceride to adipose tissue.
This efficiency makes high-fat diets energy-dense but potentially easier to overconsume.
5. The Interplay Between TEF, NEAT, and Muscle
When people lose weight, the body adapts by reducing both BMR and NEAT—a process known as adaptive thermogenesis (Rosenbaum & Leibel, Am J Clin Nutr, 2010).
Preserving lean mass through protein and resistance training mitigates this effect, maintaining both resting metabolism and spontaneous activity.
This is why at Beyond Health, we teach that “calories in, calories out” is only half the story:
Calories in, what kind, and how your body responds metabolically is the real equation.
6. Building Metabolic Resilience
To sustain a healthy metabolic rate long-term:
7. Beyond Health’s Perspective
Metabolism isn’t a single number—it’s an orchestra of systems responding to movement, nutrition, and environment.
Understanding TEF, BMR, NEAT, and AEE allows us to move beyond oversimplified diet advice toward true metabolic precision.
At Beyond Health, we help clients develop sustainable metabolic fitness—preserving lean mass, improving energy efficiency, and building resilience that extends far beyond the scale.
The goal isn’t to eat less forever—it’s to move, fuel, and recover in ways that keep your metabolism working for you, not against you.
Conclusion
Calories matter, but context matters more.
By understanding how each macronutrient and energy pathway contributes to total daily energy expenditure, you can make choices that build—not drain—your long-term metabolic health.
At Beyond Health, we see metabolism not as a weight-loss target, but as a reflection of cellular vitality and resilience—one built meal, movement, and recovery at a time.
Bibliography
