Methodology and scientific sources

Age range

Fuelia’s automatic calculator is available from age 14. It uses a dedicated method for ages 14–18 and an adult method from age 19. Fuelia uses biological sex because the cited predictive equations require that input.

Ages 14–18

Fuelia estimates resting energy with Mifflin–St Jeor. Maintenance is that estimate × 1.20, plus extra everyday movement and average daily training, both scaled proportionally with body weight.

Fuelia then applies editable, conservative goal adjustments: −10% for weight loss, −5% for recomposition, 0% for maintenance, +8% for weight gain and +5% for muscle gain. Protein supplies 15–20% of energy, fat 30%, and carbohydrate the remainder, within the AMDRs.

Ages 19 and over

Fuelia uses the same formula: Mifflin–St Jeor × 1.20, plus extra everyday movement and average daily training scaled proportionally with body weight.

The editable goal adjustments are −20%, −12%, 0%, +12% and +8% according to the goal. The protein reference starts at 1.2–1.6 g/kg; at BMI 30 or above it uses adjusted weight. Fat supplies 25–30% of energy and carbohydrate at least 45%, keeping the distribution within the AMDRs.

Water reference

The editable reminder starts at 30 ml/kg and adds 0, 150, 300 or 500 ml according to activity. It is rounded to 250 ml and limited to 1.5–3.5 litres. It is not a prescription; climate, diet, activity and health can change actual needs.

Indicative weight-goal date

The date uses the difference between estimated maintenance energy and the target with a simplified approximation of 7,700 kcal/kg. For ages 14–18, weekly rates are capped at 0.5% of weight for loss and 0.25% for gain, with absolute caps of 0.5 and 0.25 kg. From age 19, the limits are 1% and 0.5%, capped at 1 and 0.5 kg. The projection does not model metabolic adaptation, growth, adherence or fluid changes and does not promise that the displayed date will be reached.