Safety & methodology
By Thomas Freimoser · Updated: October 8, 2026
Burning 10,000 kcal in one day is an extreme experiment. This page explains honestly what that means for your body and how we calculate.
Before you start
Healthy and trained only
No infections, no heart problems. From age 35 or with risk factors we recommend a sports medical check including an exercise ECG.
Drink to thirst, with electrolytes
Too much water without salt can cause hyponatraemia: headache, nausea, confusion. Do not drink litres in advance.
Eat carbohydrates regularly
Around 60–90 g of carbohydrates per hour of effort, in small portions. Without refuelling, performance collapses.
Do not skip sleep entirely
Plan 4 to 6 hours of sleep. Sleep deprivation lowers performance and raises the risk of mistakes and falls.
Not in the heat
High temperatures raise the risk of heat exhaustion and heat stroke. Go indoors with cooling or postpone.
Stop immediately at
Dizziness, chest pain, confusion, uncontrollable cramps or dark brown urine (a sign of muscle breakdown – an emergency). Call 112 / 911.
Before the planner from 7,000 kcal and before live mode you confirm these points once. The confirmation is valid for 30 days.
Not confirmed yet.
How we calculate
No made-up numbers: the calculator uses the scientific MET table and your personal resting metabolic rate.
What your body burns in 24 hours at rest – based on weight, height, age and sex. For “diverse” we use the mean of both formulas.
male: 66.47 + 13.75 × kg + 5.00 × cm − 6.76 × age female: 655.10 + 9.56 × kg + 1.85 × cm − 4.68 × ageCalculate your own BMR
MET says how many times more energy an activity uses compared to rest. We scale MET values with your resting rate instead of a standard value – so height, age and sex count correctly.
kcal = MET × resting rate ÷ 24 × hours
Example: cycling at 19–22 km/h is 8 MET. With a resting rate of 1,865 kcal that is about 622 kcal per hour.
Sources
- Herrmann SD, Willis EA, Ainsworth BE et al.: 2024 Adult Compendium of Physical Activities. Journal of Sport and Health Science 13 (2024), 6–12 – doi:10.1016/j.jshs.2023.10.010
- Kozey S, Lyden K, Staudenmayer J, Freedson P: Errors in MET estimates of physical activities using 3.5 ml·kg⁻¹·min⁻¹ as the baseline oxygen consumption. Journal of Physical Activity and Health 7 (2010), 508–516 – doi:10.1123/jpah.7.4.508
- Harris JA, Benedict FG: A Biometric Study of Human Basal Metabolism. PNAS 4 (1918), 370–373 – doi:10.1073/pnas.4.12.370
- Shcherbina A, Mattsson CM, Waggott D et al.: Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort. Journal of Personalized Medicine 7 (2017), 3 – doi:10.3390/jpm7020003
Limits of the calculation
- MET values are averages for adults. Fitness, technique, terrain and temperature change the real burn – up or down.
- Harris-Benedict is an estimate; body fat and muscle mass are not taken into account.
- Intensity drops over the day through fatigue. The planner does not model that, which is why the daily maxima are conservative.
- Fitness trackers estimate calorie burn inaccurately. In a Stanford study of seven devices the median error for energy expenditure ranged from 27 % to 93 % (Shcherbina et al., 2017, source below). The leaderboard still counts the app's value – because it is produced the same way for everyone.
Who is behind this
I, Thomas Freimoser, run this site privately, with no company behind it. I am neither a doctor nor a sports scientist; that is why the calculation method is fully documented on this page, with the sources the numbers come from. What I cannot back up is not on here.
Found an error or have a question about the method? 91Serdar@gmail.com
Frequently asked questions
Does the resting metabolic rate count?
Yes. Every level means the total expenditure in 24 hours – the way smartwatches show it. By the Harris-Benedict formula, resting metabolism for most adults is between about 1,400 and 2,200 kcal a day; the calculator shows your own value.
Why does sleep burn calories?
Because your body is never off. Heart, breathing, brain and body heat need energy around the clock. By the Harris-Benedict formula that is 60 to 90 kcal per hour for most adults. Six hours of sleep are 400 to 550 kcal without moving at all. Watches count it, so do we.
Why do lighter people need more sport?
Calories per hour scale with the resting rate, which is lower for lighter people. A 62 kg woman has to train much harder or longer for the same target than an 80 kg man. That is why there are levels and a leaderboard by sex.
Why does my watch differ?
Watches estimate from heart rate and motion, we calculate from MET values. Both are approximations. Large differences are normal, especially for strength training and cycling.
How is a result verified?
You upload a screenshot of the day's total energy from your tracking app – Apple Health, Samsung Health, Garmin Connect, Google Fit/Fitbit or Polar Flow. Your weight and height must be correct there, otherwise the value is off. A human checks the screenshot and approves the entry. Only then do you get the verified badge and the certificate.
Why 10,000 kcal and not 10K?
Because “10K” means 10 kilometres in running. That is why we always add the calories: 10,000 kcal in 24 hours.