Trying to understand BMR and my ideal calorie restriction.

MachiavelliNZ · November 2014

Hi all,

My questions have been building up. So here goes.

CONTEXT: I know what the definition of BMR is. The number of calories I would burn in a day simply by virtue of existing. That's fine. I'm also losing weight just fine at the moment so I'm not having trouble with my diet as such, I am just trying to wrap my head around the significance of eating less than my BMR (or not!).

When I put my current weight into an online calculator it says that my BMR is 2025 calories.
However, when I put my ideal (goal) weight into a calculator it says that my BMR would become 1776.
Lastly, when I put the weight that I would be if I only weigh my current lean body mass (calculated by my Aria scale), my BMR would be approximately 1503 calories.

So here are my questions.

I'm trying to cut the flab. Why not just eat like it doesn't exist and feed only my lean body needs? Why shouldn't I just eat at 1503 calories net (eating back exercise cals)?

Same thing with the BMR of my goal weight. Surely if I just ate a net of 1776 calories (plus exercise cals to make TDEE) then my body would just recomposition itself and cut down to the size that I aim to be. Is that a stupid strategy?

Many calorie reduction plans talk about a gradual reduction in calories. Why not just go immediately to the end-game and eat the least amount of calories allowed to reach your goal? Would that be damaging or somehow detrimental?

Advice from people on the net seems to be of different minds about whether it is okay to eat under their BMR (net) and yet, at the same time, I hear tiny calorie figures touted by those doing weight loss (e.g. for me to have a BMR of 1200 cals, I would have to have 0% bodyfat and lose 20kg LBM. So clearly 1200 cals net is way, way under my BMR). I personally have been eating under my current BMR in order to get 0.7kg/week average weight loss for a few months. Am I damaging myself or is that actually fine?

I want to stay on a weight loss plan for about another 6 months so I want to be eating healthily for that period of time and not discover that I've been hurting myself by eating too little cals net. Any personal advice or linked articles that might be relevant would be greatly appreciated.

Kalikel · November 2014

Lots of schools of thought on this one, for sure!

The biggest pros to eating more (IMO) are:

- Your skin has a better shot of keeping up. Loose skin doesn't seem like a big deal when you're starting, but when you've lost a lot and have it, you might hate it. I sure do. Especially my asp, because...just trust me, lol.

- The more you lose, the harder it gets. Many experts recommend losing for six months, then maintain for a few months and then begin losing again. If you start eating more calories, you have some to drop off six (or eight or whatever) months down the line, when it gets harder.

- The more you eat, the stronger you feel and the better workouts you can have. So, in that sense, the "eat more to weigh less" crowd has a point.

- You get to eat more. So, bonus there.

If you can lose half or a full kg every week, that's great. We all have to eat less than our bodies need if were going to lose weight, but we also have to learn how to eat for life, so it's good to start making sense of how to eat right.

The bonus of eating less is that you drop a lot more pounds very quickly, for a while.

Discuss it with your doctor. Visit a dietician if you've never really paid any attention to nutrition. Hear what they have to say and then make your decisions.

Good luck!!

yarwell · November 2014

If you ate the 1776 or whatever of your ideal weight you might get to that weight, but it would take literally forever. That's if the "about 1800" is correct in the first place - we can't really talk in 4 significant figures about BMR as it just isn't that accurate - 30% of people fall outside a +/- 10% range of the prediction.

There is no issue eating less than your BMR, it's a mathematical inevitability if you are sedentary and want to lose 1 lb/week. Doctors prescribe weight loss interventions well below BMR, especially in the obese.

If you were to use the Katch McArdle BMR equation it wouldn't be fooled by excess fat and you may have a simpler reality to wrap your mind around.

focused4health · November 2014

I don't eat back exercise calories and my intake was initially set at 20% below my BMR. SO set around 1800 cals. I dropped it down to 1600 odd simply because I was eating too much. Eating when I wasn't really hungry. On days when I do a lot of exercise I do tend to eat more. But I am of the firm belief that sticking to your macro numbers is just as important. So spend some time planning your day. The app is excellent for this as you can easily see the percentages by clicking on nutrition and bring up the pie chart. I check it a few times a day but definetly before dinner and any snacks. Most days I get close but not a perfect 40.30.30

steff274 · November 2014

Is the BMR where you eat that number everyday? I am maintaining BTW typed in mine to maintain very active settings I get 2.129 calories.. I use the myfitnesspal method of eating back or trying to eat back at least half of my excersize calories I average or try to average 2500 a day.. Do actually think I would waste away on 2.129 if I ate that everyday with the activity I do would lose weight!! to the original poster what not short change yourself on calories if you are losing on a higher amount!

Vailara · November 2014

http://www.fat2fittools.com/tools/bmr/ suggests eating at the TDEE for the weight you want to be. I haven't tried it and I'm not recommending it, but there is a nice logic to it - you're basically training yourself to maintain at your goal weight, by eating what you would eat in maintenance. (They say you would have to cut calories a little more to lose as you reach goal).

They use the Harris-Benedict formula on that site to work out your TDEE. Personally, I find that gives too high a figure for me, and Katch-McArdle works better (and is similar to what I get on MFP).

I think most people who put a pound (or more) loss a week into MFP will end up netting below their BMR (and so will sedentary people who use TDEE - 20%). There do seem to be mixed feelings on whether this really matters or not. Personally, I preferred to lose quite slowly.

MachiavelliNZ · November 2014

Thanks for your thoughts, everyone. It's really helpful to hear what others think.

Kalikel wrote: »

Your skin has a better shot of keeping up. Loose skin doesn't seem like a big deal when you're starting, but when you've lost a lot and have it, you might hate it. I sure do.

... The more you eat, the stronger you feel and the better workouts you can have. So, in that sense, the "eat more to weigh less" crowd has a point.

... Visit a dietician if you've never really paid any attention to nutrition. Hear what they have to say and then make your decisions.

How quickly does loose skin tighten up? I'm 33 y/o. I started at 108kg and I'm initially aiming for 80kg. Should I expect that I will have much loose skin from that amount of loss? I really have no clue about the skin issue.

I definitely like the idea of eating better to exercise better. I do try to fuel myself well on my exercise days. And I hear that good exercise controls LBM loss while losing weight so it all sounds like it's worth doing properly.

I hadn't really considered seeing a dietician but it might be worth doing just to set myself up for success and make sure I'm not making any glaring mistakes.

yarwell wrote: »

If you ate the 1776 or whatever of your ideal weight you might get to that weight, but it would take literally forever.

... There is no issue eating less than your BMR, it's a mathematical inevitability if you are sedentary and want to lose 1 lb/week. Doctors prescribe weight loss interventions well below BMR, especially in the obese.

That sounds encouraging. I'll probably stick with the deficit that MFP gives me then until it seems like something isn't working. As I get closer to my goal weight I might ease up on the deficit.

The Katch-Mcardle BMR calculator says my BMR is 1,592. Wow! I should probably stop worrying then.

kerbsideat66 wrote: »

I am of the firm belief that sticking to your macro numbers is just as important. So spend some time planning your day.

For sure, I try to hit my macros as close as possible without becoming obsessed about it. I'm using some non MFP macros, though, because I wasn't sure how to change them in MFP at the time and now I can't be bothered changing it here

steff274 wrote: »

Is the BMR where you eat that number everyday?

BMR is the energy you need to exist. TDEE is BMR plus any daily activity. So I guess since you are active and maintaining you'll need to stick to your TDEE.

Vailara wrote: »

http://www.fat2fittools.com/tools/bmr/ suggests eating at the TDEE for the weight you want to be. I haven't tried it and I'm not recommending it, but there is a nice logic to it - you're basically training yourself to maintain at your goal weight, by eating what you would eat in maintenance. ... Personally, I preferred to lose quite slowly.

That makes a lot of sense. Obviously the fat2fittools method is the "eat how you will want to eat for life at your goal weight" approach. I'm impatient, haha! I want to hit goal weight as soon as reasonably possible and then change my fitness goal to be a %-bodyfat goal. Sexy bod here I come

TimothyFish · November 2014

If you were to eat at your goal weight BMR or even your goal weight TDEE, you would eventually reach your goal weight. Some people actually recommend this method because it trains you to eat in the way needed to maintain your goal weight once you reach it. It is, however, a slow process that gets slower as you near your goal weight.

As far as eating under BMR, I see no reason why that should be a problem. As far as calories are concerned, a calorie burns the same way whether you burned it doing exercise with an elevated heart-rate or if you burned it with your heart beating away at 60 beats per minute. The real concern is that you won't get the nutrients you need. Men need about 1500 calories to get the essential vitamins and minerals they need to survive.

Trying to understand BMR and my ideal calorie restriction.

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