Energy balance describes the relationship between energy consumed and energy used; it is a model, not a precise daily measurement. This page provides a definition and practical context; it is not an individualized medical or nutrition prescription. Use the related tools and guides for calculations or programming decisions rather than treating a glossary definition as a result.
Energy balance as a moving target, not a fixed line
Energy balance isn’t a single number you hit or miss; it’s the relationship between intake and expenditure at a given moment, and both sides of that relationship shift as your body changes. A caloric deficit or calorie surplus describes which direction you’ve deliberately tilted that balance, while TDEE is the estimate you’re comparing intake against.
Because expenditure drops as body mass drops (and rises as body mass rises), a fixed calorie target that created a deficit at the start of a diet will drift toward balance over several weeks as TDEE falls to meet it, which is the practical reason energy balance needs periodic recalculation rather than a single calculation held for months.