How Many Calories to Lose Weight
There's no universal number. Your target is your own maintenance level minus a deficit you can live with for three months — and it's arithmetic, not a mystery.
Step 1 — estimate maintenance
VECTOR90 uses the Mifflin-St Jeor equation for resting metabolic rate, then multiplies by an activity factor of 1.45 for someone training four to six days a week:
- Men: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
- Women: 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Multiply that by 1.45 and you have a realistic maintenance estimate — the intake at which your weight holds steady.
Step 2 — subtract a deficit you can hold
Bigger deficits lose weight faster and get abandoned faster. The three tracks are deliberately modest:
- −300 kcal/day → about 0.4 kg a week.
- −500 kcal/day → about 0.6 kg a week (the default).
- −750 kcal/day → about 0.8 kg a week, for a short deadline.
Over 13 weeks, the middle track is roughly 7–8 kg. The target is floored at 1,400 kcal a day — below that it's hard to hit protein and micronutrients, and adherence collapses.
Step 3 — protect muscle with protein
Losing weight without a protein target means losing some of the muscle you're training for. VECTOR90 sets 1.8 g of protein per kg of body weight and splits both calories and protein across the day — 25% breakfast, 30% lunch, 12% snack, 33% dinner — so each meal has a number attached rather than a vague instruction.
Step 4 — measure, then adjust
Every equation is an estimate; the scale is the feedback. Weigh in weekly under the same conditions and watch the trend over three to four weeks, not day to day. If the trend is flat, your real maintenance is lower than estimated — shave 100–150 kcal and check again.
Let VECTOR90 do it
Onboarding computes your maintenance, target intake, protein target and goal weight from your profile, then attaches those numbers to a 90-day plan and a weigh-in chart so you can see whether the estimate was right.
Frequently asked questions
How many calories should I eat to lose weight?
Estimate maintenance with Mifflin-St Jeor times an activity factor (1.45 if you train most days), then subtract 300–750 kcal depending on how aggressive your timeline is. Most people should not go below about 1,400 kcal a day.
Is a 1,000 calorie deficit too much?
For most people, yes — it is hard to sustain, hard to hit protein on, and tends to cost muscle. A 500 kcal deficit already produces around 0.6 kg a week, which is roughly 8 kg over a 90-day program.
How much protein do I need while losing weight?
About 1.8 g per kg of body weight is a solid target while in a deficit — it protects lean mass and keeps you full. For an 80 kg person that is roughly 145 g a day.
Why did my weight stall?
Water, sodium, and gut contents move the scale by a kilo or more, so a flat week is normal. If the four-week trend is genuinely flat, your maintenance is lower than the estimate — cut 100–150 kcal or add a conditioning session, then reassess.