Lesson from wearing a heart rate monitor for 24 hours

I decided to see how many calories I would burn in 24 hours by wearing my Polar heart rate monitor the entire day. I thought I had a pretty good idea just how many calories I would burn in 24 hours based on other tests, but I wanted to test two things. First, how accurate are these heart rate monitors, and second, if it proves accurate, how close was I to being correct. Based on my body fat testing (done by bioelectrical impedance) my basal metabolic rate is about 2100 calories per 24 hours. Basal metabolic rate is defined as the rate at which the body uses energy while at rest to keep vital functions going, such as breathing and keeping warm. With that knowledge in mind, I assumed day-to-day I probably burn about 2500 calories (after all, I’m not at rest ALL day). That would be on a non-workout day. However, I wanted to do this test on a day I exercised. So with all that information I calculated I would burn about 3,000 calories in 24 hours on a workout day. Here is what I learned:

My total burn was 3,238 calories in 24 hours. Not too bad. I was a little low on my assumption, but I also assumed my workout would burn 500-600 calories. It ended up burning 800 calories. That makes my estimate just about spot on.

24 hours. 3,238 calories.

24 hours. 3,238 calories.

Sitting is bad:

While seated and doing desk work (like I am at the moment), my heart rate touches the high 40’s but is mostly in the low 50’s range. While standing and doing miscellaneous work stuff, my heart rate is in the mid 60’s to low 70’s. This makes a huge difference and is congruent with research that shows people with sedentary jobs have higher rates of cardiovascular disease and higher mortality rates. The lesson? Get up and move.

I don’t eat enough:

In the back of my mind, I knew this. There are plenty of days where I get busy and cannot have a mid-morning or mid-afternoon snack. I need to be better about that, especially on the days I exercise. In the 24 hours I also kept track of my calories with a calorie-counting app. According to it, I consumed just over 2,500 calories. Clearly a deficit, but not necessarily a bad thing. It all depends on what you’re going for. For me, I know I do better when I at least approximate my caloric expenditure.

Heart healthy:

My average heart rate over 24 hours was just 64 beats per minute. This number is quite good. I was happy to see it. My maximum heart rate was 179 during my workout.

Burn, burn, burn:

I burn through just over 100 (somewhere between 100-110) calories an hour while awake and just under 100 calories an hour while sleeping (about 80/hour). This total excludes my exercise for the day. That is about what I expected it to be.

My heart monitor seems to be pretty accurate:

Based on the body fat testing and basal metabolic rate calculation, my heart rate monitor did a pretty good job accurately predicting calorie burn in accordance with the bioelectrical testing I did the week before.

I think the moral of the story is if you want to have the wiggle room in your diet to eat more food, you need to get up and move. I challenge anyone to try and eat 3,200 healthy calories today. It’s much harder than you think. The more you move, the more muscle you build which only adds to your ability to burn energy.

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8 Comments

Filed under Diet

8 responses to “Lesson from wearing a heart rate monitor for 24 hours

  1. Bob

    Great information!
    Quick Question, which Polar heart rate monitor is pictures above? (The one you wore for 24 hours) Thanks.

  2. Suzie

    Did you have to wet the sensor part periodically throughout the day? Thanks.

  3. Sarah

    Are you a man or woman? My Polar F4 says I burn between 3000-4000 every day without exercise and not including sleeping time! I am a cleaner though and work between 7 and 11 hours a day but I thought it might be overestimating my calories burned. I should be very skinny but I’m not, I need to lose a stone!

    • Hi Sarah –

      I am a man. I weigh about 195 pounds with a body fat of about 18%. I think your Polar F4 is probably overestimating your calorie expenditure. You’d have to get your body fat percentage measured and find out what your basal metabolic rate is. Once you figure that out, you can better estimate your caloric usage.

  4. Martin

    Hi – thanks for sharing the information. I was also keen understand my daily calorie expenditure and recently decided to use my chest strap heart rate monitor to calculate my BMR that I usually wear when working out.

    I wore it while asleep and for an hour of my typical not so active work day, sitting at my desk, getting up to get a coffee etc. These were my results:

    72 calories per hour when asleep = 576 calories based on 8 hours.
    120 Calories per hour when awake at my least active = 1920 calories (16 hours).

    Total calorie burn for 24 hours = 2496 which I take as being my BMR.

    I am male, age 43, weight (at the time of measuring) 165 pounds, height 172cm. I do HIIT at least 6 days a week for an hour (Insanity Month 2 workouts or 2 Insanity Max30 workouts consecutively) and burn an average of 600-700 calories per session which bumps up my theoretical daily calorie expenditure to 3200 (excluding after burn which I do not account for).

    However, I consume an average of 2000 calories a day (tracked through the My Fitness Pal app) in order to target fat loss at a net rate of 2 pounds per week. I am typically losing 1.5-1.75 pounds a week with the shortfall being negated by the increased muscle density (I like to think).

    Do you think my numbers stack-up?

    • Hi Martin – sorry for the delay. Given that I weigh a bit more than you, I would guess your estimate is a little high on your BMR. At 165 pounds you’re more likely to have a BMR of around 1700 calories. This is what you would burn at rest for 24 hours.

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