Lower average heart rate when dieting - is that normal?

[ScubaAlex]

I got my fitbit and Pulsar heart rate monitor that I sync with digifit for Christmas and have been pretty good at wearing both every day and especially when I work out.  I'm 44 and in pretty good shape, working out almost every day.  My heart rate for cardio classes like a spin classes used to average around 164 bpm with peaks around 175 bpm.  I started to go on a diet a few weeks ago as I need to loose a few pounds (was 142lbs and trying to get down to 135lbs) and therefore eating around 1000 cals/day.  Since then, i've noticed a considerable drop in my average heart rate down to 150 bpm with my high being 165! I feel like I'm exerting myself and putting the same amount of energy in but for some reason I can't get my heart rate up there and disappointly don't burn as many calories.

I'm not sure what else changed in my routine besides eating less and not drinking as much alcohol so I was wondering if that contributed to lowering one's heart rate.

thanks!

[Spang]

I just use the formula as a guide. I ride based on my body. I have learned to speed up or slow down as my legs dictate. Some days that means 43% high level HR with 47% just under high level. Others like this weekend I  never go fast the 47% level. It was a comfortable ride and I felt good afterwords. Will push hard this weekend -- one day.

[deweyraschick]

I have the same problem I have been intervil training for 25 years what it does is train your heart to pump a larger volume of blood so it takes less beats to satisfy the body needs. I have to teach doctors about this they want to give me a pacemaker or refuse to give an operation.  Dewey

[HopeDymond]

Wether I was thin or fat now. When ever I ate any diet plan as suggested it was always too much food and I would gain. I have to do 800 to 1000 to lose weight and gain too easily. We all are so different especially woman vs men. Not just because women’s hormones but all diseases and disorders seem to target us and we could have hypo thyroid easier than men, PCOS, pain disorders...it’s just not a perfect math equation for all. If she knows 1000 works for her then that’s her bottom line. She just didn’t realize her heart rate could have been higher due to weight or diet...and with change she brought it down...which is good as long as not too low which it doesn’t seem like it is. Just had to say something sorry lol. 

[Andreas_j]

My resting HR drops consistently about 10bpm while on a diet, ie without doing any exercise activity at all.

It drops about 1 to 2bpm each day/night,  until it plateaus. 

In my case 70bpm down to 60 +/- 2bpm, so in 5-7 days.

I have seen this each time I go on the diet 3 times so far).

My 2 cents.

[bnk87]

Last year, I found that my RHR would drop about 1 bpm/day when calorie restricted, and would rise back up when not, generally staying in the 58-64 range.  My exercise HR zones didn't seem to change.  After a sedentary break over the holidays (the holidays do last from Halloween to the Superbowl, right?), I just completed 2 weeks of calorie restriction (800-1000 cal net loss/day) and my RHR has dropped about 15 bpm over this period (from 69 to 54).  This time, my exercise HR at the same level of intensity and duration (and frequency) seems to have dropped by 10 bpm too.  Part of my diet this year is no alcohol, whereas last year I'd drink on weekends.  Not sure if this plays a role.

[Hsaxe]

I know this is old but I just wanted to throw my two cents in. I have a charge 2 and like clockwork every time I diet I see a drop in my RHR. Conversely, when I bulk, my RHR goes up. I’d be willing to bet there’s a strong correlation between my RHR and body weight. Nice to see a similar phenomenon with someone besides myself.  My opinion is that it is an indicator of metabolic adaptation to caloric restriction.  There’s a good bit of research documenting metabolic adaptation to caloric restriction, but nothing talking about its effects on RHR that I’ve found. 

[Hsaxe]

I think alcohol plays a major role. I can look at just my RHR and tell you which weekends I drank because it shoots up ~5 bpm in one day!  Takes ~2-4 day to return to normal. 

[SarahC119]

That’s interesting. I have found the same thing. When I go on a lower calorie diet my resting heart rate drops by at least 10 BPM over about a week. I was concerned this could be connected with a slower metabolism but I haven’t been able to find any information about it. My diet would still be about 1400 to 1500 cals (I’m relatively active) so I didn’t think it was low enough to slow my metabolism. I would really like some more info on this.

[Heybales]

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@SarahC119 wrote:

That’s interesting. I have found the same thing. When I go on a lower calorie diet my resting heart rate drops by at least 10 BPM over about a week. I was concerned this could be connected with a slower metabolism but I haven’t been able to find any information about it. My diet would still be about 1400 to 1500 cals (I’m relatively active) so I didn’t think it was low enough to slow my metabolism. I would really like some more info on this.

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Likely it's the lowered TEF (Thermic Effect Food) portion of your TDEE (Total Daily Energy Expenditure) as part of it.

You are eating less, so less blood flow to stomach area needed to bring nutrients to the liver for processing.

Same way if you overeat your HR will likely go up for awhile as the body deals with it.

Watch one of those "5000 calorie day challenge" videos, and the few I've seen they discuss their elevated HR.

That is part of it - it's also an aspect of the body's way of dealing with less calories than it may want.

There is a line in the sand you might say between what the body is willing to deal with and just burn more stored fat - and where it feels threatened and starts adapting by slowing you down. Less fidgeting and moving less is usually first things.

Then it's higher level basal stuff first - growing hair slower, nails, less skin replacement result in dry skin.

Then it progresses to lower level stuff like keeping you warm - many people report feeling colder when they diet too big.

Since less bodily functions as base metabolism are happening - less oxygen needed - so you are burning less.

I'd be concerned there is too much deficit being taken.

When I'm reasonable with the about of deficit - my HR doesn't lower. Perhaps there isn't much range to drop though since already fit and HR in mid 40's doesn't have much to go.