How the calorie deficit calculator works
This calculator uses the Mifflin-St Jeor equation — the most accurate predictive formula для basal metabolic rate (BMR), validated across large populations. Your BMR is the energy your body burns at complete rest. Multiply by an activity factor (1.2 sedentary → 1.9 very active) to get TDEE — total daily energy expenditure, or maintenance calories.
To lose weight, eat below TDEE. A 500 cal/day deficit produces ~1 lb/week loss (since ~3,500 calories ≈ 1 lb of fat). Larger deficits lose faster но risk muscle loss и are harder to sustain.
Why deficits are hard — and how GLP-1 medications change that
The math is simple; the adherence is brutal. Hunger, cravings, и “food noise” derail most deficits within weeks. This is exactly the problem GLP-1 medications solve: by slowing gastric emptying и acting on appetite-regulation centers in the brain, drugs like Wegovy, Zepbound, и Ozempic make a calorie deficit feel effortless. Trial participants spontaneously ate ~30% fewer calories — hitting deficits they could never maintain through willpower alone.
Not sure which medication fits your situation? Take our 60-second quiz, check whether you meet the BMI eligibility criteria, or project how much you'd lose on each GLP-1.
FAQ
What is a calorie deficit?
A calorie deficit means eating fewer calories than your body burns daily (your TDEE). The deficit forces your body to use stored fat for energy. A deficit of ~3,500 calories ≈ 1 pound of fat lost. A 500 cal/day deficit → roughly 1 lb/week.
How do I calculate my calorie deficit?
First calculate your TDEE (total daily energy expenditure) = BMR × activity multiplier. Then subtract your target deficit: 250 cal/day for 0.5 lb/week, 500 for 1 lb/week, 1000 for 2 lb/week. This calculator does both steps instantly using the Mifflin-St Jeor equation.
What is the lowest safe calorie deficit?
Never eat below 1,200 cal/day (women) or 1,500 cal/day (men) without medical supervision. Below these floors you risk muscle loss, nutrient deficiency, и metabolic slowdown. If your aggressive-deficit target falls below the floor, choose a milder deficit instead.
How do GLP-1 medications help with a calorie deficit?
GLP-1 medications (Ozempic, Wegovy, Mounjaro, Zepbound) suppress appetite by slowing gastric emptying и signaling fullness to the brain. This makes maintaining a calorie deficit feel natural rather than requiring willpower. Clinical trials show patients eat ~30% fewer calories without conscious restriction.