The equation
The calculator uses Mifflin-St Jeor, the most accurate of the common resting-metabolic-rate equations in adults with obesity: for men, 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5; for women, the same minus 161. It multiplies by an activity factor to estimate total daily energy expenditure and proposes a deficit of about 500 kcal per day, which corresponds to roughly a pound per week from diet alone.
The GLP-1 twist
Patients on tirzepatide or semaglutide rarely need help eating less. The common problem is eating too little: the medication suppresses appetite so effectively that intake can fall well below the floor, which accelerates lean-mass loss, causes fatigue and hair shedding, and makes side effects worse. The tool shows a floor as well as a target. Pair it with the protein and water tool, because protein is the nutrient most likely to be under-consumed.