The Short Answer

To lose weight you need to eat fewer calories than you burn. Most people find a sustainable rate at a deficit of roughly 500 calories a day below maintenance, which produces about 0.5 kg or 1 lb of loss per week. The US Centers for Disease Control and Prevention describes 1 to 2 lb per week as the rate most associated with keeping the weight off long term.

So the real question is not "how many calories should I eat" but "what is my maintenance level, and how much should I subtract from it".

Step 1: Find Your Maintenance Calories

Maintenance is what you burn across a normal day, known as total daily energy expenditure. It is your basal metabolic rate multiplied by an activity factor, and it is the number every calorie target is set against.

Rather than repeat the arithmetic here, we have a dedicated walkthrough: BMR vs TDEE explained covers the Mifflin-St Jeor equation, the activity multipliers, worked examples, and the mistake of choosing an activity level that flatters you.

Ballpark, if you want one now: maintenance commonly lands around 1,800 to 2,200 calories for women and 2,200 to 2,800 for men, varying widely with age, size and activity. Use the real calculation before setting a target; these ranges are only for orientation.

SlimPanda works this out during setup from your age, height, weight and goal, so you do not have to do it by hand.

Step 2: Subtract a Deficit

Take 500 off maintenance for roughly 1 lb a week, or 250 for a slower half-pound. Someone maintaining at 1,900 calories therefore lands at about 1,400 calories a day for steady loss.

Bigger deficits are not proportionally better. Very aggressive cuts tend to cost muscle alongside fat, tank energy and training quality, and are far harder to stick to, which is the variable that actually decides the outcome.

Protein Matters More Than the Rest of the Split

Total calories decide whether you lose weight. Protein largely decides whether what you lose is fat or muscle.

The adult RDA of 0.8 g per kg of body weight is a minimum for preventing deficiency, not an optimum for someone in a deficit. Research on dieting adults consistently supports higher intakes, commonly cited in the region of 1.2 to 1.6 g per kg, for preserving lean mass while losing fat. For a 70 kg person that is roughly 85 to 110 g a day.

Protein also has the highest thermic effect of the three macronutrients, meaning more of its energy is spent on digestion, and it is the most satiating per calorie. Both work in your favour during a deficit.

Practical order of priorities: hit your calorie target first, protein second, and treat the carbohydrate-to-fat split as personal preference. Diets that dictate that split tend to work because they reduce calories, not because the ratio is magic.

Adjusting When Reality Disagrees

Your calculated target is a hypothesis. Test it like one.

  1. Hold it for two to three weeks. Track intake consistently and weigh yourself on a fixed schedule.
  2. Read the trend, not the days. Compare the average of one week against the average of the next. Daily readings swing by 1 to 2 kg on water alone.
  3. Losing faster than about 1% of body weight per week? Add 100 to 200 calories back. Faster is not better; it costs more muscle and is harder to sustain.
  4. Not moving after three consistent weeks? Before cutting, check whether intake has drifted and whether your daily step count has fallen. Both are more common than a genuine metabolic issue.
  5. Recalculate every 4 to 6 kg. Maintenance falls as you get lighter, so a target set at your starting weight slowly stops being a deficit.

The Floors You Should Not Cross

Widely used clinical guidance puts the lower bound for unsupervised dieting at roughly 1,200 calories a day for women and 1,500 for men. Below that it becomes difficult to hit basic micronutrient needs from food alone, and very low calorie diets belong under medical supervision rather than in a self-directed plan.

If your calculated target lands under those numbers, the answer is usually to increase activity rather than cut food further.

Why the Numbers Drift

Every part of this is an estimate. Mifflin-St Jeor is a population average, so an individual can sit meaningfully above or below it. Activity multipliers are broad bands. Food labels carry a permitted margin of error. Your own expenditure also falls as you lose weight, simply because a smaller body costs less to run.

Treat the calculated figure as a starting hypothesis, not a fact. Track for two or three weeks, watch the trend rather than daily readings, and adjust by 100 to 200 calories if the trend is not moving the way you want.

Track It Without the Spreadsheet

SlimPanda works out a starting calorie target from your age, height, weight and goal, then tracks what you actually eat against it.

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Frequently Asked Questions

How many calories should I eat to lose weight?
Estimate your maintenance calories with the Mifflin-St Jeor equation multiplied by an activity factor, then subtract about 500 a day for roughly 1 lb of loss per week. For many adults that lands somewhere between 1,400 and 2,000 calories, but it depends on age, height, weight, sex and activity.
Is 1,200 calories a day enough?
1,200 is widely treated as the lower bound for women dieting without medical supervision, and 1,500 for men. It is a floor, not a target. If your calculated deficit falls below it, increase activity instead of cutting food further, and speak to a doctor or dietitian.
How fast should I lose weight?
The CDC associates about 1 to 2 lb per week with better long-term maintenance. Faster loss is possible but tends to cost more muscle, is harder to sustain, and is more likely to be regained.
Do I need to count calories forever?
No. Most people track closely for a period to learn the calorie content of the foods they actually eat, then move to lighter tracking. The habit knowledge tends to persist even when daily logging stops.
Does exercise mean I can eat more?
Yes, but usually less than people expect. Fitness trackers and machines tend to overestimate calorie burn, so eating back the full estimate often erases the deficit. A common approach is to eat back only part of it, or to build activity into your maintenance figure and leave it there.
Health disclaimer. SlimPanda and these guides are for general information and self-tracking only. They are not medical advice, diagnosis or treatment, and calorie and hydration figures produced by any app are estimates. Talk to a doctor or registered dietitian before starting a weight-loss plan, and especially if you are pregnant or breastfeeding, under 18, over 65, managing diabetes, heart, kidney or thyroid conditions, taking prescription medication, or have any history of disordered eating. If food, weight or exercise feels distressing or out of control, please speak to a health professional rather than a tracking app.