question about netting BMR and fitbit

Ange_

Ok i'm just trying to get my head around this.

I use my fibit to workout my TDEE accurately. My average over a week including workout and a non workout day is 2300cals per day.

So if i want to eat the same thing every day i should eat 2300-15% which is 1955 cals
That's fine, i get that.

But now to this thing about netting over your BMR.
i don't really like the way MFP counts exercise calories as it doesn't minus your BMR from that workout period. So i'd rather use my fibit as a more accurate measure of my true activity level for the day as it takes my HRM readings for a workout and takes into account the portion of that reading that was already counted as my BMR for the day before working out the total energy expenditure.

Netting is kind of a term that more applies to MFP than fitbit. Fitbit doesn't really distinguish between energy expended from daily activity or exercise which is what i kind of like but makes it difficult to figure out this netting your BMR bit.

But say on a day i burnt 500 calories doing some kind of exercise and ate say 2000 cals. MFP would tell me i netted 1500 cals which is under my BMR of 1600. So then presumably so long as i burn 400 cals or less a day i don't need to eat more.
but how does this account for the fact that the 2300 number was worked out as an average including my rest day not exercising. My TDEE was worked out including most days burning more than 400 cals a day from exercise. So if i ate more on the days i burn more than 400 i'll actually have less of a cut than 15%. And why should only exercise count and not varied daily activity?

Also for fibit/bodymedia etc users. It might be nice if there is a maximum deficit number/percentage rather than this business about net BMR even though we are logging our food on MFP. Fitbit says how many cals are burnt and how many i've eaten and the difference between the 2.

Thanks.

Daphnemomof9

I also find this to be a bit tricky. I use a fitbit but find that the calorie adjustment, to MFP, is not accurate. It can be anywhere from 100 and something to almost 300 calories off otherwise I think I could just input my exercise on fitbit and use the BMR total.

Throughout the day I try and guesstimate where I'm at with my calorie burn by seeing where I currently am at and multiplying the hours I have left by 80 calories, that's usually the bare minimum for me, which is all I usually expend at the end of the day and I can kind of guage how far off the adjustment is and change it (in my mind) to determine my BMR. If that makes any sense at all. I still appreciate having a fitbit to give me a much better idea of how many calories I burn in a day.

You suggested taking the amount of calories you burn by working out as a way of determining your BMR, but I find that depending on what my day has going on, my daily burn (besides workouts) can fluctuate quite a bit.

Glitter969

That's a very interesting question. I also use a fitbit but I have never even thought about it in so much detail. So I am also interested in other responses.

I think it is the one challenge of using a fitbit to calculate TDEE if you have bigger differences between workout and non-workout days, but wanting to eat a set number of cals a day and maintain a 15% cut. My TDEE differs by up to 800 cals a day. So far I have only really looked at my HRM exercise to calculate net BMR (ie excluding the fitbit adjustment). Somehow it feels to me that it would balance things out if that makes any sense.

Ange_

You suggested taking the amount of calories you burn by working out as a way of determining your BMR, but I find that depending on what my day has going on, my daily burn (besides workouts) can fluctuate quite a bit.

Do you mean TDEE not BMR?
I know what my BMR is already as it is determined by my height and weight, not by exercise. TDEE is exercise+daily movement+BMR.

Sorry just trying to work out if i understood you.
Good idea about estimating the rest of the evening's calories. I could easily do that too.