How to Increase BMR — Boost Your Resting Metabolism

What BMR Measures

Basal Metabolic Rate (BMR) is an estimate of how many calories your body would burn in a 24-hour period if you stayed completely at rest — awake, lying still, comfortable room temperature, in a post-absorptive state (not digesting a recent meal). BMR represents the energy cost of keeping all your vital systems running: the heart, lungs, brain, liver, kidneys, and every other organ and tissue performing the thousands of chemical reactions required simply to stay alive.

BMR is the single biggest component of total daily energy expenditure for most adults, typically accounting for 60 to 75 percent of total calories burned each day. The rest comes from non-exercise activity thermogenesis, purposeful exercise, and the thermic effect of food. Knowing your BMR helps you design realistic calorie targets for weight change, maintenance, or athletic performance fueling.

The Two BMR Formulas

This calculator presents two of the most widely used BMR estimation formulas side by side so you can compare. Neither is perfect — both estimate within a typical population error band of about ±5 to 10 percent for individuals where no measured metabolic data is available.

1. Mifflin-St Jeor Equation (Published 1990)

The Mifflin-St Jeor equation was published in 1990 by Mifflin et al. at Oregon State University after reviewing 114 studies and validating against a large sample of measured indirect calorimetry results. Multiple independent reviews, including a 2005 analysis in the Journal of the Academy of Nutrition and Dietetics, have concluded Mifflin-St Jeor is generally the most accurate population-level formula for most modern adults.

2. Harris-Benedict Equation (Revised 1984 by Roza & Shizgal)

The original Harris-Benedict equation dates to 1918-1919, developed by James Arthur Harris and Francis Gano Benedict using calorimetry data from 239 men and women. A 1984 revision by Roza and Shizgal updated the constants using more modern measurement techniques on a larger sample. The revised Harris-Benedict formula remains common in many evidence-based and older software systems, though it typically produces results slightly different from Mifflin-St Jeor depending on age and body size.

Worked Example

For a 30-year-old male, 175 cm, 70 kg. Mifflin-St Jeor: (10 × 70) + (6.25 × 175) − (5 × 30) + 5 = 700 + 1093.75 − 150 + 5 = 1648.75 kcal/day ≈ 1649 kcal/day. Revised Harris-Benedict: 88.362 + (13.397 × 70) + (4.799 × 175) − (5.677 × 30) = 88.362 + 937.79 + 839.825 − 170.31 ≈ 1696 kcal/day. The two formulas give answers about 47 kcal apart for this example — a difference of roughly 3 percent.

FAQ-Style Explanations

Why are the two formulas different? They were derived on different populations at different times using different measurement equipment. Harris-Benedict was developed on a small, mostly European-origin sample in the early 1900s. Mifflin-St Jeor was developed in 1990 using a larger and more diverse sample. The differences reflect the underlying data more than any deep disagreement about human metabolism.

Which one should I use? For most adults, use the Mifflin-St Jeor number as your primary estimate. If you already know from experience how many calories you need to maintain your current weight, compare it to both formulas and pick whichever is closer to your personal reality. If you are very muscular, very elderly, or have a medical condition affecting metabolism, both formulas will be less accurate and a measured resting metabolic rate test would give you a better answer.

Does BMR decrease with age? Yes, on average. After roughly age 20, BMR declines approximately 2 to 3 percent per decade in most people. This decline is largely driven by sarcopenia — the gradual loss of muscle mass that occurs with aging when strength training is not maintained. Regular resistance training and adequate protein intake can slow this decline substantially and preserve metabolic rate into older age.

Known Limitations

• Estimates only. Real resting metabolic rate can only be measured directly via indirect calorimetry or a doubly labeled water study.
• Do not account for body composition. Two people with identical height, weight, age, and sex can have very different BMR if one has much more muscle than the other.
• Do not account for thyroid function, regular health products, fever, pregnancy, lactation, or metabolic conditions.
• Less accurate at the extremes of body size (very high or very low BMI) and for people of non-European ethnic backgrounds where the original validation samples were thin.
• BMR is not a target to eat at — it is the minimum. Almost everyone needs significantly more calories than BMR in daily life.

Build Muscle — The Most Effective Lever

The single most effective way to raise Basal Metabolic Rate is to increase your skeletal muscle mass through resistance training. Skeletal muscle is metabolically active tissue that burns calories around the clock, even at rest, while adipose tissue burns comparatively little. Adding lean mass raises the baseline energy your body needs just to maintain itself, which lifts BMR over the long term. The effect per kilogram of muscle is modest — often estimated at a few extra calories per kilogram per day at rest — but it compounds over months and years, and it shifts body composition favorably. Resistance training two to four times per week, focusing on compound movements like squats, deadlifts, presses, and rows, builds the muscle that keeps resting metabolism higher for years to come.

Why Resistance Training Beats Cardio for BMR

Cardiovascular exercise burns plenty of calories during the session, which makes it valuable for overall energy balance, but it does relatively little to raise BMR long term because it builds minimal muscle. Resistance training, by contrast, creates the muscle damage that drives growth, and the new lean tissue then burns extra calories every day at rest. Cardio also has a place — it supports heart and lung fitness and adds to daily expenditure — but for raising BMR specifically, lifting is the priority. A balanced routine pairs two to four strength sessions per week with moderate cardio, giving you both the muscle that raises resting metabolism and the cardiovascular conditioning that supports overall fitness.

Protein and the Thermic Effect of Food

Digesting and processing the food you eat costs energy, a phenomenon called the thermic effect of food (TEF). Protein has the highest TEF of the three macronutrients — roughly 20 to 30 percent of its calories are burned just breaking it down and absorbing it — compared with about 5 to 10 percent for carbohydrates and 0 to 3 percent for fat. Eating enough protein therefore slightly raises overall daily expenditure beyond the calories on the label. A target of 1.2 to 1.6 grams per kilogram of body weight suits most adults, rising to 1.6 to 2.2 grams per kilogram for those building muscle. Protein also supports the lean mass that keeps BMR elevated, so it works on two fronts at once.

Sleep and the Danger of Extreme Diets

• Poor sleep lowers resting metabolic rate and disrupts the hormones that regulate hunger and fullness. Aim for 7 to 9 hours per night to keep metabolism running cleanly.
• Extreme calorie restriction triggers metabolic adaptation, where the body lowers BMR to conserve energy. This is why very low-calorie diets often stall and then rebound.
• Take a moderate deficit of 300 to 500 calories below TDEE for fat loss, and take diet breaks of a week at maintenance every 6 to 12 weeks to let metabolism recover.
• Stay hydrated, manage stress, and keep caffeine intake moderate — small habits that support a stable, healthy resting metabolism alongside training and protein.