Energy sustains basic functions, movement, growth and repair. It is not a substance but usable energy from protein, carbohydrate, fat and alcohol.
Individual; depends on body size, body composition, activity and goal.
All energy-containing foods; oils, nuts and high-fat foods are especially energy dense.
Sustained low energy availability can cause weight loss, feeling cold, fatigue, menstrual disruption, impaired performance and loss of muscle and bone mass.
Chronic under-fuelling can contribute to malnutrition and relative energy deficiency in sport (RED-S); chronic excess promotes weight gain.
Weight trajectory and performance decline can offer clues but are not specific.
Higher with restrictive diets, eating disorders, elite sport, illness, poor appetite and frailty.
Assess weight, growth, menstrual function, training performance and intake together over time.
No pill replaces adequate food. Oral nutrition support can be useful in medically assessed undernutrition.
Long-term energy excess increases body fat; effects also depend on food quality, activity and metabolism.