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BMR Calculator

Calculate the calories your body burns at rest — the baseline your fasting metabolism runs on.

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Your Basal Metabolic Rate is the starting point for understanding your body's energy needs. It tells you the minimum number of calories required just to keep your body functioning, before any movement or activity is factored in.

For intermittent fasting practitioners, understanding BMR is particularly valuable. It helps you ensure that even on fasting days you are providing your body with enough fuel during eating windows to support essential functions without compromising your metabolic health.

Frequently Asked Questions

What exactly is Basal Metabolic Rate?
BMR is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulating blood, cell production, and maintaining body temperature. It represents the energy you would burn if you stayed in bed all day doing absolutely nothing.
Which BMR formula is the most accurate?
The Mifflin-St Jeor equation, published in 1990, is considered the gold standard by the American Dietetic Association. It tends to be more accurate than the older Harris-Benedict equation, particularly for overweight individuals.
Does intermittent fasting lower your BMR?
Short-term intermittent fasting (up to 48 hours) does not significantly lower BMR and may actually increase it slightly due to norepinephrine release. Prolonged calorie restriction over weeks, however, can lower BMR regardless of whether you practise IF.
How does BMR change with age?
BMR typically decreases by about 1-2% per decade after age 20, primarily due to loss of lean muscle mass. Strength training and maintaining muscle through adequate protein intake can help slow this decline significantly.
Can I increase my BMR naturally?
Yes. Building lean muscle mass through resistance training is the most effective way to raise BMR, since muscle tissue burns more calories at rest than fat tissue. Staying well-hydrated, getting adequate sleep, and eating sufficient protein also support a healthy metabolic rate.

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Fasting Timer

Free intermittent fasting timer that runs in your browser. Start your fast, watch metabolic phases update live, and get notified when your window closes.

See your body's fat burning phases in real time with Fasted

The Fasted app shows you exactly when your body shifts from burning glucose to burning fat during a fast, giving you real-time insight into your metabolism.

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