What Are the Two Main Factors That Impact Energy Balance?

October 29, 2025 •

4 min read

With the global prevalence of overweight and obesity continuing to rise, understanding what are the two main factors that impact energy balance has become more crucial than ever. This fundamental concept of balancing calories consumed versus calories burned is key to maintaining a healthy weight and overall metabolic health.

Quick Summary

Energy balance is determined by the relationship between energy intake and energy expenditure. Positive or negative balance leads to weight gain or loss, influenced by complex factors like diet, hormones, and physical activity.

Key Points

Energy Intake and Expenditure: The two main factors impacting energy balance are the calories you consume and the calories you burn.
Positive vs. Negative Balance: Consuming more energy than you expend leads to weight gain (positive balance), while expending more than you consume leads to weight loss (negative balance).
Expenditure Components: Your total energy expenditure consists of your Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and physical activity.
Hormonal Influence: Hormones like ghrelin (hunger) and leptin (satiety) play a significant role in regulating your appetite and energy intake.
Adaptive Thermogenesis: The body can adapt its energy expenditure in response to prolonged changes in intake, making weight loss or gain more challenging over time.
Holistic Approach: Effective energy balance management requires a holistic approach, considering diet, exercise, sleep, and stress levels.

The concept of energy balance is defined by a simple equation: Energy Balance = Energy Intake - Energy Expenditure. However, the factors influencing each side of this equation are complex and vary significantly among individuals. A positive energy balance, where intake exceeds expenditure, leads to weight gain, while a negative balance causes weight loss. Maintaining a neutral, or stable, energy balance over time is the key to maintaining a consistent body weight.

Energy Intake: The "Calories In" Side of the Equation

Energy intake (EI) refers to the energy consumed from foods and beverages. It is the fuel your body receives to function. Calories are derived from the macronutrients in food:

Carbohydrates: Provide 4 kilocalories per gram.
Protein: Also provides 4 kilocalories per gram.
Fats: The most energy-dense, providing 9 kilocalories per gram.
Alcohol: Also contributes calories at 7 kilocalories per gram.

Factors Influencing Energy Intake

Consuming food isn't just a matter of willpower; it's a complex process regulated by a variety of signals:

Physiological Factors: Hormones like ghrelin (the hunger hormone) stimulate appetite, while leptin (the satiety hormone) signals fullness. The hypothalamus in the brain acts as a central regulator of feeding behavior.
Psychological Factors: Stress and emotions can significantly impact eating patterns, often leading to comfort eating or emotional eating.
Environmental Factors: The availability, accessibility, and marketing of food heavily influence our choices. Large portion sizes are a well-documented driver of increased calorie consumption.
Dietary Composition: The type of food eaten matters. A diet rich in protein, for instance, can increase satiety more effectively than a high-fat or high-carbohydrate meal.

Energy Expenditure: The "Calories Out" Side of the Equation

Energy expenditure (EE) is the total number of calories your body burns to perform all its functions. It is comprised of three main components:

Basal Metabolic Rate (BMR): The energy required to keep your body functioning at rest. This includes vital processes like breathing, blood circulation, and cell production. For sedentary individuals, BMR accounts for 60-75% of total energy expenditure.
Thermic Effect of Food (TEF): The energy used to digest, absorb, and process the nutrients from the food you eat. It typically accounts for about 10% of your total energy expenditure and varies based on macronutrient composition.
Physical Activity: The most variable component of EE, covering everything from planned exercise to everyday movements. It is further divided into:
- EAT (Exercise-related activity thermogenesis): Planned, structured physical activity like running or strength training.
- NEAT (Non-exercise activity thermogenesis): Energy expended during daily, unstructured activities such as fidgeting, walking, and standing.

Factors Influencing Energy Expenditure

Multiple factors determine an individual's EE, some of which are beyond our control:

Genetics: Inherited traits can influence metabolic rate, with some individuals having naturally faster or slower metabolisms.
Age: Metabolic rate generally slows with age, often due to a gradual loss of muscle mass.
Body Composition: Individuals with more muscle mass have a higher BMR than those with more fat mass, as muscle tissue is more metabolically active.
Hormones: Thyroid hormones are major regulators of metabolic rate. Hormonal imbalances can either slow down or speed up metabolism.

Comparison of Energy Intake vs. Energy Expenditure


Aspect	Energy Intake (Calories In)	Energy Expenditure (Calories Out)
Primary Function	Provides the body with fuel from consumed food and drinks.	Utilizes calories for resting functions, digestion, and physical activity.
Key Components	Macronutrients (carbohydrates, fats, proteins), alcohol, etc.	BMR, TEF, Physical Activity (EAT & NEAT).
Regulation	Influenced by physiological (hunger/satiety hormones), psychological (stress), and environmental factors.	Influenced by genetics, age, gender, body size, and physical activity level.
Variability	Can be consciously managed by diet choices, portion control, and meal timing.	Can be influenced by lifestyle but also has a large inherent component (BMR).
Impact on Weight	Excess intake over expenditure leads to weight gain (positive energy balance).	Expenditure exceeding intake leads to weight loss (negative energy balance).

Practical Lifestyle Tips for Managing Energy Balance

Achieving and maintaining a healthy energy balance involves making conscious choices regarding both sides of the equation. Small, consistent changes can have a significant impact over time.

Balance Macronutrients: Choose a balanced diet with a variety of foods from all food groups, focusing on lean proteins, whole grains, fruits, and vegetables to help manage satiety and energy levels.
Increase Physical Activity: Incorporate regular exercise and increase non-exercise activity (NEAT). Take the stairs, walk during breaks, or stand more often to boost daily calorie expenditure.
Manage Portion Sizes: Being mindful of portion sizes is a simple way to control energy intake. Using smaller plates or measuring servings can help.
Prioritize Sleep: Poor sleep can disrupt hormonal balance, increasing hunger and decreasing energy expenditure. Aim for 7-9 hours of quality sleep per night.
Stay Hydrated: Staying well-hydrated is crucial for metabolic function and can also help control appetite.
Manage Stress: Chronic stress can lead to increased cortisol levels, which influences appetite and fat storage. Practices like meditation and yoga can help.
Cook at Home More: This allows for greater control over ingredients, portion sizes, and preparation methods, helping to reduce intake of high-calorie, processed foods.

For more dietary guidance, consult the World Health Organization's facts on healthy diets.

Conclusion

Maintaining energy balance isn't as simple as a purely mathematical equation due to the complex interplay of physiological, genetic, behavioral, and environmental factors. However, the fundamental principle remains the same: balancing energy intake and energy expenditure is key to managing body weight. By understanding the components of both sides of the equation and implementing sustainable lifestyle changes—such as adopting a balanced diet, increasing physical activity, and managing stress—individuals can effectively manage their energy balance and promote long-term health and well-being.

Frequently Asked Questions

Energy balance is the relationship between the energy you consume through food and drinks (energy intake) and the energy your body uses for vital functions and physical activity (energy expenditure).

A positive energy balance occurs when you consume more calories than you burn. When this is sustained over time, the body stores the excess energy, primarily as fat, leading to weight gain and an increased risk of metabolic diseases.

A negative energy balance happens when you burn more calories than you consume. This forces your body to use stored energy (fat and glycogen), leading to weight loss. However, a prolonged and severe deficit can negatively impact metabolism, concentration, and hormone levels.

Metabolism directly influences energy expenditure, particularly your Basal Metabolic Rate (BMR). Factors like age, body composition, and genetics determine how many calories your body burns at rest, which significantly impacts your overall energy balance.

Yes, hormones like ghrelin and leptin play a critical role in regulating energy balance by controlling hunger and satiety signals that are sent to your brain. Disruptions in these hormonal systems can contribute to weight issues.

Exercise increases energy expenditure, helping to create a calorie deficit for weight loss or maintain a neutral balance. It also builds muscle mass, which increases your basal metabolic rate, helping you burn more calories even at rest.

Yes, genetics can play a role in energy balance by influencing an individual's metabolic rate and their predisposition to fat accumulation. However, lifestyle and environmental factors also significantly impact weight regulation and overall health.