How is energy balance defined in nutrition?

• A. Calories consumed minus calories expended; when intake equals expenditure, weight is stable.
• B. Only calories expended matter; intake is irrelevant.
• C. Only calories consumed matter; expenditure is irrelevant.
• D. It is a fixed value independent of activity.

Answer: (A)

Energy balance is the relationship between what you eat (energy intake) and how much energy your body uses (energy expenditure). It is defined as calories consumed minus calories expended. When intake equals expenditure, weight tends to stay the same. Expenditure comes from several sources: your basal metabolic rate (the energy needed to keep organs functioning at rest), the thermic effect of food (energy used to digest and process nutrients), and energy used during physical activity and daily movements. If you consistently take in more energy than you burn, the surplus is stored, usually as body fat, leading to weight gain. If intake is less than expenditure, stored energy is released, leading to weight loss. The idea isn’t fixed or one-sided; activity levels and metabolism can change, shifting the balance as needed. The other statements oversimplify by ignoring either intake or expenditure, or by claiming energy balance is independent of activity.