If you've ever wondered why one person can eat more than another without gaining weight, or why weight loss won't budge no matter how hard you try, the answer is often found in your basal metabolic rate.
What does BMR mean?
BMR stands for Basal Metabolic Rate. It tells you how many calories your body burns at complete rest — just to keep you alive. Your heart, lungs and brain, along with cell renewal, all require energy even if you don't move a muscle.
For a typical adult, BMR falls somewhere between 1,400 and 2,000 kcal. It's the number of calories you'd burn if you lay on the sofa all day without moving at all.
How is BMR calculated?
There are several formulas. RestinCal uses the Mifflin-St Jeor formula, currently considered the most accurate for the average person:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (yr) + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (yr) − 161
For example, a 30-year-old man weighing 75 kg and 175 cm tall:
10 × 75 + 6.25 × 175 − 5 × 30 + 5 = 1,724 kcal/day
That's the baseline. But it doesn't yet tell you how much you actually need.
BMR vs. TDEE — what's the difference?
BMR is only the starting point. In real life you need TDEE (Total Daily Energy Expenditure), which accounts for your activity:
| Activity level | Multiplier | Example |
|---|---|---|
| Desk job, no exercise | × 1.2 | Office work with no hobbies |
| Light exercise 1–3 days/wk | × 1.375 | A couple of walks a week |
| Moderate exercise 3–5 days/wk | × 1.55 | Gym a few times a week |
| Heavy exercise 6–7 days/wk | × 1.725 | Athlete level |
The same 30-year-old man with moderate activity: 1,724 × 1.55 = approx. 2,672 kcal/day. That's how much he needs to maintain his weight.
What do you do with this?
- Weight loss: Eat 300–500 kcal below your TDEE. This produces about 0.3–0.5 kg of loss per week — slow enough to preserve muscle.
- Maintenance: Eat at your TDEE.
- Muscle gain: Eat 200–300 kcal above your TDEE, with enough protein.
The numbers are always estimates — the formula doesn't know your body fat percentage, your hormone levels or how well you sleep. But it gives a solid starting point you can fine-tune based on real-world tracking.
The most common misconceptions
- "BMR slows down dramatically when dieting." A little, yes — the body adapts. But the change is typically 5–15%, not a halving. Long starvation diets are more harmful than a moderate deficit.
- "I have a slow metabolism." Rarely the real explanation. In studies, the variation between people of the same size is surprisingly small. Most often the problem is underestimating calories — not metabolism.
- "The activity multiplier is accurate." It isn't. Most people overestimate their activity. If you're unsure, pick a lower multiplier and watch your actual weight change over a few weeks.