“How many calories should I eat per day?” It is one of the most searched questions in health and fitness — and the answer is different for every person. In this article we follow Maya (38, 160cm, 80kg) and Robin (20, 186cm, 60kg) as they discover their exact calorie needs and what to do with that information.
Meet Maya — 38 Years Old, 160cm, 80kg
Maya is a working mother who wants to lose weight. She has tried various diets over the years but never really understood how many calories she actually needs. Her doctor told her to “eat less” — but less than what exactly? Maya decided to find out properly.
Meet Robin — 20 Years Old, 186cm, 60kg
Robin is a university student who wants to gain muscle and weight. He eats what feels like a lot but never seems to put on any weight. His gym trainer told him he needs to “eat more” — but again, how much more? Robin decided to calculate it properly too.
First — What is a Calorie?
A calorie is simply a unit of energy. Every food and drink you consume provides energy measured in calories. Your body uses this energy for everything — breathing, thinking, moving, digesting, and even sleeping.
When you eat more calories than your body burns — you gain weight. When you eat fewer calories than you burn — you lose weight. When they match — your weight stays the same. This is the fundamental principle behind every diet and nutrition plan ever created.
What is TDEE — Your Personal Calorie Number
TDEE stands for Total Daily Energy Expenditure. It is the total number of calories your body burns in a day — including your resting metabolism, digestion, and all physical activity. Your TDEE is your personal maintenance calorie number — eat at this level and your weight stays the same.
Research reference: The Dietary Guidelines for Americans 2020–2025 — published by the US Department of Health and Human Services — estimates daily calorie needs range from 1,600 to 2,400 calories for women and 2,000 to 3,000 calories for men depending on age and activity level. However your personal TDEE can be calculated much more precisely using the Mifflin-St Jeor equation — the most validated formula used by dietitians worldwide.
Source: Dietary Guidelines for Americans 2020–2025. US Department of Health and Human Services.
How is TDEE Calculated? Step by Step
TDEE is calculated in two steps. First we calculate BMR (Basal Metabolic Rate) — the calories your body burns at complete rest. Then we multiply by an activity factor.
The Mifflin-St Jeor Formula:
Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
Calculating Maya’s Daily Calories
Let us work through Maya’s numbers. She is 38 years old, weighs 80kg, and is 160cm tall. She has a desk job and walks occasionally — making her lightly active.
Step 1 — Maya’s BMR:
BMR = (10 × 80) + (6.25 × 160) − (5 × 38) − 161
BMR = 800 + 1000 − 190 − 161
BMR = 1,449 calories
Step 2 — Maya’s TDEE (lightly active × 1.375):
TDEE = 1,449 × 1.375
Maya’s TDEE = 1,992 calories per day
This means Maya needs approximately 1,992 calories per day just to maintain her current weight of 80kg. Since Maya wants to lose weight her doctor recommended a calorie deficit.
Maya’s Weight Loss Calorie Target:
TDEE − 500 calories deficit = 1,992 − 500 = 1,492 calories per day
At this intake Maya will lose approximately 0.5kg (1 lb) per week — a safe and sustainable rate.
Maya’s daily macro targets:
Protein: 130g (to preserve muscle while losing fat)
Carbs: 130g
Fats: 50g
Calculating Robin’s Daily Calories
Now let us work through Robin’s numbers. He is 20 years old, weighs 60kg, and is 186cm tall. He goes to the gym 3 times per week — making him moderately active.
Step 1 — Robin’s BMR:
BMR = (10 × 60) + (6.25 × 186) − (5 × 20) + 5
BMR = 600 + 1162.5 − 100 + 5
BMR = 1,667 calories
Step 2 — Robin’s TDEE (moderately active × 1.55):
TDEE = 1,667 × 1.55
Robin’s TDEE = 2,584 calories per day
This means Robin needs approximately 2,584 calories per day just to maintain his current weight of 60kg. Since Robin wants to gain muscle his trainer recommended a calorie surplus.
Robin’s Muscle Gain Calorie Target:
TDEE + 300 calories surplus = 2,584 + 300 = 2,884 calories per day
At this intake Robin will gain approximately 0.25–0.5kg per week — a healthy rate for lean muscle gain.
Robin’s daily macro targets:
Protein: 150g (to support muscle growth)
Carbs: 350g
Fats: 80g
The Surprising Insight — Robin Needs More Calories Than Maya Despite Weighing Less
This is one of the most important insights from Maya and Robin’s story. Despite Robin weighing 20kg less than Maya, he actually needs almost 900 more calories per day than she does. Why?
- Robin is taller — more body mass means higher base metabolism
- Robin is younger — metabolism is naturally faster in the early 20s
- Robin is male — men generally have higher muscle mass and faster metabolism than women of the same weight
- Robin exercises more — gym sessions significantly increase calorie needs
This is exactly why generic calorie advice like “eat 2,000 calories a day” doesn’t work for everyone. Your calorie needs are completely personal.
Calorie Needs by Age and Activity Level
Here is a general reference table based on the Dietary Guidelines for Americans — a useful starting point before calculating your personal TDEE:
| Age Group | Women (sedentary–active) | Men (sedentary–active) |
|---|---|---|
| 19–30 years | 1,800 – 2,400 kcal | 2,400 – 3,000 kcal |
| 31–50 years | 1,800 – 2,200 kcal | 2,200 – 3,000 kcal |
| 51–70 years | 1,600 – 2,200 kcal | 2,000 – 2,800 kcal |
| 71+ years | 1,600 – 2,000 kcal | 2,000 – 2,600 kcal |
Source: Dietary Guidelines for Americans 2020–2025. US Department of Health and Human Services.
What Happens if You Eat Too Few Calories?
Maya made a mistake in her first attempt at dieting — she cut her calories to just 900 per day, thinking more restriction meant faster results. Here is what actually happened:
- Her metabolism slowed down — the body adapts to low calorie intake by becoming more efficient, burning fewer calories
- She lost muscle — without adequate protein and calories the body breaks down muscle for energy
- She felt exhausted and foggy — the brain needs glucose to function — severe restriction affects concentration and mood
- She regained all the weight — extreme restriction leads to rebound eating and weight regain
Important: Never eat below 1,200 calories per day for women or 1,500 calories per day for men without medical supervision. Going below these thresholds for extended periods causes muscle loss, nutrient deficiencies, and metabolic adaptation that makes future weight loss harder.
What Happens if You Eat Too Many Calories?
Robin made a different mistake — he started eating 4,000 calories a day thinking more food meant more muscle. What actually happened was different from what he expected:
- He gained fat, not just muscle — excess calories beyond what training can use get stored as fat regardless of the source
- He felt sluggish — overeating causes digestive stress and energy crashes
- His gym performance suffered — carrying excess body fat actually reduces athletic performance
The lesson — a moderate surplus of 200 to 500 calories above TDEE is all that is needed for optimal muscle gain. More than this just adds unnecessary fat.
Maya and Robin — 3 Months Later
Both Maya and Robin followed their calculated calorie targets consistently for 3 months.
Maya’s Results
Starting weight: 80kg
Current weight: 73.5kg
Lost: 6.5kg in 13 weeks
Daily calories: 1,492 kcal
Maya now has more energy, sleeps better, and has dropped a clothing size. She still has 9.5kg to go to reach her goal weight of 64kg but she is well on track.
Robin’s Results
Starting weight: 60kg
Current weight: 65kg
Gained: 5kg in 13 weeks
Daily calories: 2,884 kcal
Robin is visibly stronger and his BMI has moved from 17.3 to 18.8 — into the healthy range. His gym performance has improved significantly and he no longer feels constantly fatigued.
Practical Tips for Hitting Your Calorie Target
- Track for at least 2 weeks — use a free app like MyFitnessPal or Cronometer to understand what you are actually eating. Most people are surprised how different their estimates are from reality.
- Prioritise protein — hitting your protein target first makes hitting your calorie target much easier. Protein is the most filling macronutrient and helps preserve muscle during a deficit.
- Eat whole foods mostly — whole foods are naturally more filling per calorie than processed foods, making it easier to stay within your target without feeling hungry.
- Adjust after 3 weeks — if you are not seeing results after 3 weeks of consistent eating, adjust by 100 to 200 calories up or down. Your calculated TDEE is an estimate — real results tell you the truth.
- Don’t stress occasional days — one day of eating over your target won’t derail weeks of progress. What matters is your average intake over time, not any single day.
- Recalculate as you lose or gain weight — as your body weight changes your TDEE changes too. Recalculate every 5 to 10kg of weight change to keep your targets accurate.
Calculate Your Personal Calorie Target
Just like Maya and Robin — find your exact daily calorie and macro targets in seconds. Free, no signup needed, works in both metric and imperial units.
Calculate My Calories Free →The Bottom Line
Maya needed 1,492 calories per day to lose weight. Robin needed 2,884 calories per day to gain muscle. Both numbers were calculated from the same formula — applied to their individual stats. Your number will be completely different from both of theirs — and that is exactly the point.
There is no universal answer to “how many calories should I eat.” But there is a precise personal answer — and now you know exactly how to find it.
References
- Dietary Guidelines for Americans 2020–2025. US Department of Health and Human Services and US Department of Agriculture.
- Mifflin MD, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. 1990;51(2):241-247.
- Wu G. Dietary protein intake and human health. Food & Function. 2016;7(3):1251-1265. National Institutes of Health / PubMed.
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Disclaimer: This article is for informational and educational purposes only. The characters Maya and Robin are fictional and created for educational illustration. Always consult a qualified healthcare professional or registered dietitian for personalised nutrition guidance.