Accurately Calculate Your Basal Metabolic Rate (BMR)
Lean is the only app that calculates your BMR based on your body fat percentage.
Lean calculates your metabolism using the most up-to-date scientific models — those based on body fat percentage (% body fat).
Your lean body mass (your weight minus fat mass) is the most influential factor in determining your metabolic rate. That’s why your body fat percentage is the most critical data point for accurately calculating your BMR.
BMR (Basal Metabolic Rate)
Your BMR (Basal Metabolic Rate)is the term used in scientific literature to describe the energy your body expends at rest. It represents the energy your organs (brain, heart, kidneys, muscles…) use to perform vital functions such as breathing, blood circulation, and maintaining body temperature.
In your total daily energy expenditure, BMR accounts for between 50% and 90% , making it by far your body’s largest energy expense.
How does it work?
1. Weigh Yourself
In the Lean app, you’ll need to log your weight as frequently as possible — at least 2 to 3 times per week, and ideally every day.
One of Lean’s innovative features is that instead of relying on your daily weight, Lean calculates your 7-day average weight.Why? This approach smooths out temporary fluctuations — caused by hydration, fatigue, food intake, or hormonal changes — and gives you a more accurate and reliable view of your body’s progression.
2. Calculate Your Body Fat Percentage
Lean includes a built-in bodyscan : an algorithm that analyzes a photo of your body and estimates your body fat percentage with a precision of ±2%, which is within the accepted margin for the theoretical model used.
It couldn’t be simpler: each week or month, update your body fat using Lean’s Body Scan. This body fat percentage will then be used to evaluate your Basal Metabolic Rate (BMR) accurately.
Women naturally have a higher body fat percentage than men!
Track Your Progress
Lean is the only app that lets you monitor your metabolism week by week and understand how it evolves over time.
Lean recalculates your metabolism daily based on the data you enter into the app — always giving you the most accurate and realistic values possible..
Why Is Lean Different?
Lean uses advanced theoretical models based on body fat percentage to calculate your BMR. Most other apps still rely on outdated models like Harris-Benedict which have significant margins of error.On average, the Harris-Benedict model can be off by 300 to 400 kcal per day, enough to completely derail your progress.
Model
Harris-Benedict
1500 kcal/day
❌
Model
Lean
✅
In addition, most energy expenditure calculators — whether online or built into other apps — use static equations that provide only rough estimates of your Total Daily Energy Expenditure (TDEE).
Lean adapts your metabolism constantly based on your lifestyle (weight, body fat, step count, workouts) and eating habits..
Accounting for
Metabolic Adaptation
This is likely Lean’s most powerful innovation: It takes into account the metabolic adaptation your body undergoes during a calorie deficit — a key factor that’s often ignored by other apps.
When you enter a calorie deficit and start losing weight, your body activates self-preservation mechanisms to conserve energy. The consequence?
- Your Basal Metabolic Rate (BMR) decreases.
This means traditional metabolism formulas are no longer accurate once metabolic adaptation kicks in.
Lean Has Built a Proprietary Model Lean accurately calculates your metabolic adaptation throughout your calorie deficit phase:
- Metabolic Adaptation 100% Your body is not undergoing any adaptation. Your BMR remains stable.
- Metabolic Adaptation 90% et 98% You're in a calorie deficit. Your BMR has decreased by 2% to 10% from its theoretical value.
- Below 90% Metabolic Adaptation: You've been in a long and intense calorie deficit. It's best to return to calorie maintenance to recover.
✅ Lean handles everything automatically — and always factors in metabolic adaptation when setting your recommended calorie target.
Complete Lean Tutorial
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How to Increase Your BMR ?
Your Basal Metabolic Rate (BMR) is your body’s main source of energy expenditure — so optimizing it should be a top priority.
To do this, let’s break down BMR into energy consumption by organ group:
| Organ Group | Contribution to BMR |
| Muscles | 30% |
| Liver | 25% |
| Brain | 20% |
| Heart | 10% |
| Kidneys | 5% |
| Fat tissue | 3% |
| Other (skin, gut...) | 7% |
Muscles are the top contributors to your energy expenditure. The more muscle mass you have, the higher your BMR.
💪 Strength training and muscle building are powerful tools to boost your metabolism and support fat loss.
The EAT section in Lean is designed for this: log your workouts in the app to precisely track the calorie burn generated by your training sessions.
FAQ
Why Aren’t Models Like Harris-Benedict Reliable ?
Traditional models (Harris-Benedict, Mifflin-St Jeor, Black et al.) don’t include body fat percentage in their input data. As a result, they treat all body weight as if it were the same. This leads to major inaccuracies:
- For Overweight individualsexcess fat is falsely interpreted as muscle → BMR overestimated.
- For Underweight individuals:lack of fat is interpreted as lack of muscle → BMR underestimated.
- For Athletes/active people ou un sportif régulierhigh muscle mass is ignored → BMR underestimated.
In short: if you're not the Vitruvian Man, abandon these models — they weren’t made for you.
How Do BMR, NEAT, and EAT Interact?
Both NEAT (Non-Exercise Activity Thermogenesis) and EAT (Exercise Activity Thermogenesis) depend directly on your BMR. The energy needed to move — whether it's exercise or just daily activity — varies based on the amount of muscle involved.
Striking example: Let’s Take Two Extreme Cases as Examples:
- A 50 kg woman, not engaged in sport, burns about 0.02 kcal per step..
- A 210 kg strongman burns about 0.08 kcal per step..
That’s a 4× difference in energy expenditure per movement.
Bottom line: increasing your BMR indirectly boosts both your NEAT and your EAT.
For more details:
How to Manage Metabolic Adaptation During a Calorie Deficit?
When your metabolic adaptation drops to around 90% (or below), it means your BMR has decreased by about 10%. Since both NEAT and EAT depend on BMR, this means your total TDEE has also dropped by roughly 10%.
➡️ It might not sound like much, but it's significant. If your TDEE was 3000 kcal, a 10% drop = 300 kcal less per day — a big deal in a calorie deficit!
The best approach in this case is to return to calorie maintenance in order to reset your metabolic adaptationYou won’t gain weight, since you'll be eating at maintenance. Your metabolic adaptation will gradually recover, and once it reaches around 97%–100%, you’ll be able to confidently start a new fat loss cycle.
How to Take Your Body Scan in Optimal Conditions ?
To get the most accurate body fat scan, follow the in-app instructions carefully:
- Position yourself precisely within the silhouette shown on the screen
- Take a deep breath
- Exhale fully
- Slightly contract your abs
For even more accurate results:
- Always scan under the same conditions, in the same location, with the same lighting
- Avoid scanning right after a workout, when your muscles are pumped
- Stand at an appropriate distance from the camera — not too close
Don’t hesitate to adjust the body fat manually or retake the scan if the result seems inconsistent
What’s the Body Fat Accuracy Level?
The scan has a margin of error of ±2%, which is within the acceptable range for the model used.
What Theoretical Model Does Lean Use to Calculate BMR?
Lean uses a proprietary model developed by its Research & Development team, specifically designed to factor in body fat percentage and individual metabolic behavior — unlike outdated models like Harris-Benedict.
Try Lean for free!
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