Interesting findings today

[xyber]

Just thought I'd post this up as some may find this interesting and helpful.

I've been using a Fitbit pedometer and associated site for a few years and it has shown a fairly steady 4000 calorie a day burn, from waking to going to bed. (I'm a courier)

I am currently 102kg and have been for over 12 months, even at 750-1000 calorie a day deficit. My diet is good, I commute by bike, drink very little, walk 5 miles a day and on a Sunday tend to do 20-40 miles of hard cycling.

Something wasn't adding up as to why my weight wouldn't budge!

So last night I had an idea and today I wore my fitbit as usual, but also a heart rate monitor.

I've just got home from work and found these results..

Reported calorie burn...
Fitbit 3084
Heart rate monitor 4356

So if I eat to my normal calorie budget, whereas I thought I was having a 1000 calorie a day deficit, in reality it's closer to 2250 calories!!!!

Now, correct me if I'm wrong, but I think at that level my body will be holding on for dear life to fat.

Time for me to eat more I think.

Anyone else had a similar experience?

[PaleoCrossfit]

@xyber in theory, absolutely correct.

That being said, I would recommend wearing the hear rate monitor for at least a week or two to really get an accurate baseline.

@Heybales can give you some great advice on this as well.

[xyber]

Yes I was going to do the same all next week to get a decent average baseline as today wasn't a particularly busy day for me either.

[Heybales]

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@xyber wrote:
Yes I was going to do the same all next week to get a decent average baseline as today wasn't a particularly busy day for me either.

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Sadly, the HRM isn't going to be valid for all day wear, and possibly not your walking if you are fit enough.

The formula HRM use for estimating calorie burn from HR are totally based on the need to provide oxygen as fuel to burn, and part of that is estimating your fitness level.

As such it's ONLY valid in the aerobic exercise zone for steady-state.

The exercise zone has been shown in studies to start about 90 for most people. Under is not exercise so not valid. Anaerobic like lifting and sprints isn't either, that's over, and not steady-state HR the same for 2-4 minutes either.

If you have cheaper Polar, then it is assuming bad BMI (height/weight) means bad fitness level (age/gender) as shown by VO2max.

So I'm betting you may not reach 90 BPM anymore with your fitness level, or at least not often. I don't walking 4 mph flat. Carrying 20 lb backpack I can reach 110, more if slight incline.

So accuracy of HRM calorie burn is still off at lower end anyway.

I wouldn't waste battery wearing it all day, unless curious what the HR is doing. Because the calorie count will be totally invalid.

That's why step based is more accurate under that exercise zone.

Now, that being said, your device isn't going to know about you carrying extra weight either, or inclines and desclines carrying extra weight - so it is indeed underestimating calorie burn.

And it's estimate of distance with heavier impacts than your logged weight would imply means it thinks you are moving faster and distance is off, so that might be the only saving point, but I'll bet it's still not as accurate with extra weight.

[xyber]

That's annoying. Guess I'll just have to experiment with higher cal intake then and see what happens/works.

Thanks for the reply. I didn't realise the pedometer read anything more than just all impacts being equal.

[Rodshaz]

 Im 50 and 110 kilos. Im in the same boat. 1000 cal deficit is not enough. Im kooking to eat 1800 cals with a 2000 cal deficit. I walk 12 to 15,000 steps each day and cycle twice a week

[Heybales]

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@Rodshaz wrote:

 Im 50 and 110 kilos. Im in the same boat. 1000 cal deficit is not enough. Im kooking to eat 1800 cals with a 2000 cal deficit. I walk 12 to 15,000 steps each day and cycle twice a week

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With that deficit and that type of exercise - count on probably the normal 20% of your weight loss being muscle mass.

Considering how hard a time you'd have trying to add it back on being 50 - I'd suggest don't risk it.

If you were doing a progressive weight lifting routine, and eating in surplus willing to gain some fat, you could probably get 1 lb in 4-6 weeks of muscle added back. Along with same or more fat.

Better not to lose what you got.

If you aren't losing 2 lbs weekly already with a 1000 cal deficit, then examine the basics first.

Are you logging everything you eat by weight?

Calories is per gram, not cup or spoonful, so weigh in grams everything and get servings correct.

Are you manually logging workouts with calorie burns based on something else that could be inflated, so not really burning as much as you think?

Then again, you could be needing to manually log workouts the Fitbit can't be good at estimating.

If you've already been undereating for awhile and body is stressed out and adapted slower, then you could keep eating less and accept the muscle loss, or let your body speed back up, and take a reasonable deficit.

[Rodshaz]

Thanks for the advice. Ive been measuring and weighing my food so ill see how this goes.