Total daily energy expenditure (TDEE)

Your total daily energy expenditure (also called total energy requirement) is the energy your body uses over a whole day – while sleeping, sitting, walking, digesting and exercising. It's the key reference point: if you eat roughly that much, your weight stays stable; if you eat a little less, you lose weight; if you eat more, you gain weight.

Total energy expenditure is made up of three parts. Basal metabolic rate – the energy for your organs and basic bodily functions – accounts for 60 to 70% in most people. Digestion, known as diet-induced thermogenesis, costs around 10%. The rest, about 15 to 30%, is movement: planned exercise and – often underestimated – everyday activity such as climbing stairs, tidying up, shopping or fidgeting.

It's calculated by multiplying your basal metabolic rate by your PAL value (physical activity level), a figure that reflects how active you are. Example: a basal metabolic rate of 1,410 kcal × 1.4 (mostly sitting) gives around 1,970 kcal; with an active everyday life and a PAL of 1.7, it would be about 2,400 kcal. As guide values for adults aged 25 to 51 who don't move much, the German Nutrition Society (DGE) gives around 1,800 kcal for women and 2,300 kcal for men.

Two things you should know: first, these are averages – real people can differ by several hundred calories. Second, your total energy expenditure changes – it falls as your weight goes down and rises with more muscle and more everyday movement. So recalculate it every few kilos.

For children and teenagers, energy needs vary widely depending on age and growth phase; figures from adult calculators don't apply. In any case, their total energy expenditure isn't a target to hit or stay below – in children, hunger and fullness regulate this surprisingly well, as long as the right food is on offer.