Energy Balance, Body Composition, and Eating Disorders: Key Concepts and Methods

Energy Equilibrium

When energy intake (calories consumed) matches energy expenditure (calories burned), resulting in weight stability.

Positive Energy Balance

Intake exceeds expenditure, leading to weight gain (essential during pregnancy, infancy, and childhood).

Negative Energy Balance

Expenditure exceeds intake, leading to weight loss.

Basal Metabolism (BMR)

The minimum amount of energy expended in a fasting state to keep a resting, awake body alive. It accounts for 60-70% of total energy expenditure.

Physical Activity

Increases energy expenditure above basal needs; the most variable component of total energy output.

Thermic Effect of Food (TEF)

The energy used to digest, absorb, transport, store, and metabolize nutrients. It accounts for 5-10% of total energy expenditure.

Adaptive Thermogenesis

Energy expended for non-voluntary physical activity triggered by cold conditions or overfeeding (e.g., shivering, fidgeting).

BMI (Body Mass Index)

A ratio of weight to height used to estimate body fatness.

Underweight

< 18.5

Healthy

18.5 - 24.9

Overweight

25 - 29.9

Obese

≥ 30

Underwater Weighing

A method of estimating body fat by measuring body density; it is considered one of the most accurate 'gold standard' methods.

DEXA (Dual Energy X-ray Absorptiometry)

The most accurate clinical method for measuring body fat, bone density, and lean mass.

Android (Upper-Body) Obesity

'Apple' shape; fat stored in the abdominal region. Higher risk for heart disease and type 2 diabetes. Common in men.