Calculate how many calories you burn during exercise
Calorie burn during exercise is estimated using Metabolic Equivalent of Task (MET) values — a standardised measure of energy expenditure relative to rest. One MET equals approximately 3.5ml of oxygen per kilogram of body weight per minute, which translates to roughly 1 kcal per kg per hour at rest.
The calculation is: Calories = MET × weight in kg × duration in hours. A 70kg person walking briskly (MET ≈ 4.5) for 30 minutes would burn approximately: 4.5 × 70 × 0.5 = 157.5 calories. This is the same formula used in most consumer calorie calculators and fitness wearables.
MET values are measured in laboratory conditions on populations of subjects. Individual variation in factors like fitness level, movement efficiency, and muscle composition creates significant variance in real-world calorie burn. A highly trained runner expends fewer calories per kilometre than a beginner, because more efficient movement requires less metabolic work. This means calorie estimates for exercise are directionally useful but should not be used as precise measures for dietary planning.
Research consistently shows that humans compensate for exercise-induced calorie expenditure through several mechanisms: increased hunger leading to greater food intake, reduced spontaneous movement (NEAT — non-exercise activity thermogenesis) after formal exercise, and metabolic adaptations over time. Studies of weight loss interventions find that exercise alone, without dietary change, produces much smaller weight loss than calorie calculations suggest. Exercise is valuable for health, cardiovascular function, mental health, and metabolic rate maintenance — but it is a poor weight loss tool in isolation.
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