'Net' calories and BMR
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MimGSR
Posts: 61 Member
I've heard a lot on here that your net calories should be higher than your BMR. But I don't quite understand the science behind it.
My BMR is 1500, TDEE is 2100. If I eat 1600 calories then in reality I'm netting -500.
I understand that eating tiny amounts of calories for a sustained period can harm the metabolism, and that the less you eat the less likely you are to get enough nutrients, but if occasionally I ate 1450 calories (and netted -650 instead) would it really matter? By the end of the day my body must be using body fat/muscle for energy, even for BMR, so why is eating less then BMR such a big thing?
It's all hypothetical (I eat 1700ish) but another thread got me thinking and I didn't want to hijack it!
My BMR is 1500, TDEE is 2100. If I eat 1600 calories then in reality I'm netting -500.
I understand that eating tiny amounts of calories for a sustained period can harm the metabolism, and that the less you eat the less likely you are to get enough nutrients, but if occasionally I ate 1450 calories (and netted -650 instead) would it really matter? By the end of the day my body must be using body fat/muscle for energy, even for BMR, so why is eating less then BMR such a big thing?
It's all hypothetical (I eat 1700ish) but another thread got me thinking and I didn't want to hijack it!
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Replies
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I've heard a lot on here that your net calories should be higher than your BMR. But I don't quite understand the science behind it.
My BMR is 1500, TDEE is 2100. If I eat 1600 calories then in reality I'm netting -500.
I understand that eating tiny amounts of calories for a sustained period can harm the metabolism, and that the less you eat the less likely you are to get enough nutrients, but if occasionally I ate 1450 calories (and netted -650 instead) would it really matter? By the end of the day my body must be using body fat/muscle for energy, even for BMR, so why is eating less then BMR such a big thing?
It's all hypothetical (I eat 1700ish) but another thread got me thinking and I didn't want to hijack it!
"Net calories" means the calories you eat minus the calories you burn with exercise. So your net in the example is still 1600. If you worked out for half an hour and burned 150 calories, then your net would be 1450 (1600 - 150).
With the MFP method, your net should be your MFP calorie goal. Hope that makes sense!0 -
That makes sense, but why are the calories I burn with exercise different to the calories I burn at the gym/through day to day activities? If my calorie input minus output for the whole day is -500 why does it matter that calories in minus calories-burnt-at-the-gym is less than my BMR?0
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That makes sense, but why are the calories I burn with exercise different to the calories I burn at the gym/through day to day activities? If my calorie input minus output for the whole day is -500 why does it matter that calories in minus calories-burnt-at-the-gym is less than my BMR?
It doesn't. But most people on MyFitnessPal are using the NEAT method where they assume a certain number of base calories for their normal daily activity, and then log and eat back workout / exercise calories on top of that.
If you're using TDEE-20%, you can ignore the distinction.0 -
That makes sense, but why are the calories I burn with exercise different to the calories I burn at the gym/through day to day activities? If my calorie input minus output for the whole day is -500 why does it matter that calories in minus calories-burnt-at-the-gym is less than my BMR?
Your BMR is the calories your body would burn if you just lay in bed all day. Your body needs energy to do basic things like breathe, digest, repair cells, grow hair, stuff like that. If you are not giving it enough calories to do this, it will start using your muscle tissue for fuel or just not functioning properly, which is why people with EDs will suffer hair loss, stop menstruating, become forgetful. You should really net your BMR to ensure health, unless you are under a doctor's care and very obese.0 -
imho I don't think net matters as long as you are getting enough gross calories. The goal is a deficit afterall. I have found the more i eat the bigger deficit i can feel fine with too. So its much easier to burn 4500 calories in a day when i eat 3000, than it is to burn 3000 on a day when i eat 2000...even with less net, better performance
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That makes sense, but why are the calories I burn with exercise different to the calories I burn at the gym/through day to day activities? If my calorie input minus output for the whole day is -500 why does it matter that calories in minus calories-burnt-at-the-gym is less than my BMR?
Your BMR is the calories your body would burn if you just lay in bed all day. Your body needs energy to do basic things like breathe, digest, repair cells, grow hair, stuff like that. If you are not giving it enough calories to do this, it will start using your muscle tissue for fuel or just not functioning properly, which is why people with EDs will suffer hair loss, stop menstruating, become forgetful. You should really net your BMR to ensure health, unless you are under a doctor's care and very obese.
with adequate protein and resistance training the muscle loss will be minimal, especially if this is say 3 days out of 7 each week with a much bigger deficit0 -
But say for arguments sake, you burn the same amount of calories constently throughout the day. If I have a TDEE of 2100 on average I would burn 87.5 calories per hour. If I east 1500 calories it would take me just over 17 hours to burn through them. So for the last 7 hours of the day all the calories I use, including the calories I use to respire etc, will be from body fat/muscle. So for part of the day my BMR will be getting energy from body fat/muscle anyway. So why is BMR the magic number to eat?
Like I said, I know it doesn't apply to me (and I know I'm being very pedantic, i just don't understand!) as I'm doing tdee-20%, but I've seen so many people on here saying that is terrible to eat below your BMR over the years and I'm just trying to understand if there is any real science to back that up.0 -
longtimeterp wrote: »That makes sense, but why are the calories I burn with exercise different to the calories I burn at the gym/through day to day activities? If my calorie input minus output for the whole day is -500 why does it matter that calories in minus calories-burnt-at-the-gym is less than my BMR?
Your BMR is the calories your body would burn if you just lay in bed all day. Your body needs energy to do basic things like breathe, digest, repair cells, grow hair, stuff like that. If you are not giving it enough calories to do this, it will start using your muscle tissue for fuel or just not functioning properly, which is why people with EDs will suffer hair loss, stop menstruating, become forgetful. You should really net your BMR to ensure health, unless you are under a doctor's care and very obese.
with adequate protein and resistance training the muscle loss will be minimal, especially if this is say 3 days out of 7 each week with a much bigger deficit
Doesn't that depend on how low you are netting? In the previous thread OP is referring to, another user said they were eating 1900 cals and burning 1000, so they were netting 900 calories. At some point, don't you get low enough that it's not possible to be getting enough protein?0 -
By the end of the day my body must be using body fat/muscle for energy, even for BMR, so why is eating less then BMR such a big thing?
Simple answer: it's not. Your body has no idea if you are above or below BMR.
In many cases (not all) it's a decent approximation for not having an overly aggressive deficit, but especially if you have lots to lose or are sedentary, being below BMR may not be especially aggressive.
As for not being below BMR with net calories (vs gross), never actually heard that one before. Usually the argument there is that women shouldn't net below 1200 and men not below 1500 (IMO, it depends on context).0 -
I think I might have confused myself now
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That makes sense, but why are the calories I burn with exercise different to the calories I burn at the gym/through day to day activities? If my calorie input minus output for the whole day is -500 why does it matter that calories in minus calories-burnt-at-the-gym is less than my BMR?
The argument here is that if you do intense exercise it may need more to sustain it than if you just do lots of lower level activity through the day. When I used to bike commute to work I considered that daily activity, because it didn't seem to take as much out of me as hard exercise. I don't know if that's a legitimate distinction or not, though.
More to the point, there's a natural limit on how aggressive you can be doing TDEE in that normally anything more than -20% (or sometimes 25%) is not recommended. When people do MFP method there's a greater risk of being overly aggressive in that they might pick -2 lb/week (or a 1000 deficit) and then exercise on top of that for a really low net calorie number.0 -
lemurcat12 wrote: »Simple answer: it's not. Your body has no idea if you are above or below BMR.
In many cases (not all) it's a decent approximation for not having an overly aggressive deficit, but especially if you have lots to lose or are sedentary, being below BMR may not be especially aggressive.
As for not being below BMR with net calories (vs gross), never actually heard that one before. Usually the argument there is that women shouldn't net below 1200 and men not below 1500 (IMO, it depends on context).
Thank you, I thought this was the case but was confused about it.
Thank you to everyone who's answered, I know I haven't been making much sense!
Edited to fix the quote0 -
Doesn't that depend on how low you are netting? In the previous thread OP is referring to, another user said they were eating 1900 cals and burning 1000, so they were netting 900 calories. At some point, don't you get low enough that it's not possible to be getting enough protein?
Net calories has no bearing on total macro intake, that is gross calories. Any the adaquate protein argument goes between 1g/kg and 1g/lb...so for a 200lb person that is between 100-200g of protein, or 400-800 gross protein calories.
edit...except there is nothing gross about protein, i love it, my favorite macro!
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I asked a similar question earlier today regarding BMR and net cals: http://community.myfitnesspal.com/en/discussion/10159735/mfp-setting-cal-goal-at-below-bmr#latest0
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What MFP calls net and what everyone else calls net are two different things. MFP adds your goal to you net, so a true zero net it when your food minus your exercise calories equals your goal. Whether that is above or below BMR really doesn't matter.0
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Thank you, I've think you've confirmed what I thought, that your body doesn't know if you've netted BMR and it's not the magic be all and end all.
The post below was the one that confused me, but I've heard it a few times in the 3+years I've been here (lost a few stone and maintained until getting pregnant, trying to lose the baby weight now).Giving you the benefit of the doubt on your numbers ...
1900 consumed - 1000 exercise burn = 900 calories. From that 900 calories we must now subtract your resting metabolic rate which is going to put you at negative net calories for the day. If that is in fact what you are doing, it is unhealthy.0 -
Thank you, I've think you've confirmed what I thought, that your body doesn't know if you've netted BMR and it's not the magic be all and end all.
The post below was the one that confused me, but I've heard it a few times in the 3+years I've been here (lost a few stone and maintained until getting pregnant, trying to lose the baby weight now).Giving you the benefit of the doubt on your numbers ...
1900 consumed - 1000 exercise burn = 900 calories. From that 900 calories we must now subtract your resting metabolic rate which is going to put you at negative net calories for the day. If that is in fact what you are doing, it is unhealthy.
The person is correct about it putting you at a negative net calories for the day, but you can't lose weight if you aren't at a negative net calories. But by how much? It is recommended that you don't go below -1000. So, as long as the persons BMR isn't greater than 1900, they haven't exceeded the recommendation.0 -
Yeah, that's what I replied, that being at negative net calories is a calorie deficit and what we're hoping to achieve!
Are there any studies to support -1000? A programme I was watching the other day had people at a 1500+ deficit.0
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