The best deficit isn't the biggest one — it's the one you can hold while keeping your energy, muscle, and sanity intact. Here's how to size it properly from the start.
A deficit is a subtraction from your total daily energy expenditure — what you actually burn in a day — not from some round figure like 1,200. Get your TDEE first, then subtract. A common, sustainable subtraction is 300–500 calories a day, which produces loss of roughly 0.5–1% of body weight per week. See how fast is safe.
The deficit should never push your intake below your BMR — the energy your body needs at rest. Eat below that and you tend to lose muscle alongside fat, feel exhausted, struggle to get enough protein, and find the plan impossible to sustain. Both the calculator and planner enforce this floor automatically.
Aggressive deficits accelerate muscle loss and metabolic adaptation and are far harder to adhere to — and adherence is the single biggest predictor of success. A moderate deficit followed for months beats a severe one abandoned in week three. It also leaves you somewhere to go: when loss slows, you have room to trim further rather than already being at rock bottom.
Keep protein high and include resistance training so the weight you lose is fat, not muscle. Then recalculate as you go — your deficit shrinks as you get lighter, so recalculate every 10–15 lbs or use the tracker to keep the target honest against your real results.
Usually 300–500 calories below your TDEE, producing roughly 0.5–1% of body weight lost per week. Keep intake above your BMR.
Severe deficits cause more muscle loss, faster metabolic adaptation, and poor adherence. A moderate, sustainable deficit loses fat more reliably over time.
Recalculate as you lose weight (every 10–15 lbs or when you stall), keep protein high, and train with resistance to preserve muscle.