Is eating 4% below BMR really that bad?

CM9178

I understand that if you use "sedentary tdee" that I need to eat back exercise calories.
But you said that you shouldn't eat at 20% deficit if you are sedentary and not exercising.
My question was why would these calculators even give you a tdee-20% calculation for sedentary, if you shouldn't do that much of a deficit? It doesn't make sense to me that they are just "assuming" that I will exercise on top of that number. If they wanted me to exercise, then sedentary shouldn't even be an option. Do you know what I'm saying?

I want to point out that I'm not arguing with any of the advice being given here. But I see a lot of advice thrown around without an explanation behind it. If I am going to follow the advice of someone - I want to understand the reasoning behind why I should be doing something.

The calculators give you a TDEE-20% calculation for sedentary because they assume you will be adding exercise calories on top of the number that you get.

I personally set my calorie goal to about TDEE - 20% for sedentary. I add exercise calories back on top of that.

If I did no exercise, I would not set my calorie goal to TDEE - 20% for sedentary.

The reason I recommend not doing that is because eating a significant calorie deficit while doing no exercise is a recipe for muscle loss, poor cardiovascular health, fat maintenance, fatigue, and general feelings of tiredness and lethargy.

Perfectly safe to eat slightly below your BMR when sedentary, especially if you have 40 lbs to lose.

Ok, I understand what you are saying.
So basically, to answer my original question - since I am not currently exercising, I should not use TDEE - 20%.
I should use a lower deficit for now.

If I begin exercising, I can increase the deficit to 20% and it would be ok to be slightly under my BMR.

Correct?

Yes, that would be my recommendation.

Ok makes sense.

How accurate do you think the TDEE calculators are that don't include body fat (since I don't have a caliper to measure body fat). ?

They seem to be really good for normal people actually. Pretty much everyone I know that followed them lost weight at expected speed.

Good to know!

So problem now is, you say its ok to be a little below BMR (if i'm exercising) because it isn't a magical number and I should be more concerned about the size of my deficit.

Yet others here say the BMR is what you need in a coma and you should never, ever eat below it.

So who is right?

it is perfectly safe for you to eat below your BMR given you are sedentary and especially because you have 40 lbs to lose. Your body is going to metabolize your excess fat to make up your deficit. Try to keep your protein consumption to .8-1 g / lb of LBM.

thanks, this makes sense.

marinachan83

Oh man you're concerned with that. I must be doing something very wrong then. My work out set me at 1200cal a day without exercise. I'm having trouble just eating that much. I'm just not hungry : /. Does the calorie intake depend on height? Now I feel the need to do research before asking more dumb questions.

Mads1997

There is no problem eating under your bmr especially if you have lots of fat stores. I am under the care of a dietician. I walk 40 mins 3 times a week and lift weights 3 to 4 times a week. I have maintained my LBM whilst eating under my bmr.

SteelySunshine

It's fine. You are talking 60 calories under -- this is well within the range of estimation error. You don't know your BMR exactly, the calorie content of your food exactly, or the amount you are eating exactly. The "don't eat under your BMR" rule is something you only see advocated here on MFP and is basically a way of advising against very large deficits as a way to lose weight -- you would not fall into that category.

Yeah, that is what I was going to say. But, it bears repeating. 60 calories aren't that many. No one eats exactly the same calories everyday or burns the exact same calories everyday. So, there is a margin of error. But, I wouldn't advise overeating 60 calories a day everyday, it will still add up.

Vorenus85

Oh man you're concerned with that. I must be doing something very wrong then. My work out set me at 1200cal a day without exercise. I'm having trouble just eating that much. I'm just not hungry : /. Does the calorie intake depend on height? Now I feel the need to do research before asking more dumb questions.

It's not personal but I almost get angry seeing posts like yours. I struggle to gain enough exercise calories just to be able to eat at a deficit, and it STILL feels like I'm not eating much. I guess I can't fathom how someone could struggle to reach such a low calorie amount, especially considering how quickly calorie dense foods can fill that gap (eg: peanut butter, avacados or just junk food).

ninerbuff

And what exactly is the reason for that? You don't have to exercise to aid in weight loss, it just prevents muscle loss.

And as you lose weight, you'll lose muscle, which means your metabolic rate slows even faster than from just weight loss alone.

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FluffyMcNutter

There is obviously a margin of error when using calculators for BMR and TDEE. Eating under your true BMR (not the guesstimate) for long periods of time can be counter-productive because the body will figure out how to use less energy to function (out of necessity), which will lower your metabolism. Lower metabolism is clearly not great for fat loss or weight loss.

As I understand the math, 3500 calories = 1 lb of fat, whereas 600 calories = 1 lb of muscle. So, when your body is trying to figure out what to burn when it isn't getting enough energy (calories), it's going to choose some combination of the two because it's more efficient for the body to break down LBM. Muscle helps to keep your metabolism up, so it's kind of a double whammy to lower metabolism by not eating enough and then to further reduce it by losing muscle. That's why it's important to do some resistance training, so that your muscles are being used and aren't seen as a good source of energy for the body to deplete.

That's where the whole thing about not eating TDEE-20% while being truly sedentary comes in. You are essentially giving your body permission to burn muscle (and therefore less fat). That's a good way to set yourself up for becoming 'skinny fat,' which means you're probably going to have to make an additional lifestyle change in the future. Can you do it? Certainly. Is it the best path? Hard to imagine it is. Eating at TDEE-15% or 10% while being truly sedentary just gives your body less permission to burn LBM. It'll probably still happen, but to a lesser extent. Theoretically, that means you wouldn't have as much to overcome later as you would eating TDEE-20%. It think that's why so many people get fairly up-in-arms about the prospect of eating less with no exercise. It's just setting up a more difficult road later.

As this applies to you, I don't think your body is going to shut down by eating 4% below your guesstimate BMR. If I were you, I'd probably opt for 15% in the short-term, though. It doesn't appear that you're unwilling to exercise, just that you are unable for the time being. That leads me to believe that in the future, you will be willing to, so more potential muscle loss seems like a bad idea because it will just make it more difficult for you when you are well enough to engage more fully in exercise (specifically resistance training). I do think it's great that you're working on doing some dumbbell work, no matter the weight. You aren't going to be burning a lot of calories, so I wouldn't even worry about that aspect of it. You should try to keep in mind, though, that you don't need to do high reps with the weights. Start out at 3 lbs, but as you gain some strength and you find that you can do sets of 15 reps without failure, you should try to increase to 5 lbs, etc. That's just going to use your muscles more and therefore help you to preserve them.

All of what I've said could certainly be wrong, but it makes more sense to me than a lot of the other approaches I've seen. Good luck!

lithezebra

I wish my BMR were above 1500. The more calories you have to play with, the easier it is to get those all important nutrients. I might occasionally eat below my BMR, but I would not make a habit of it. You just end up being tired, moving less, and not thinking as well because your brain isn't properly fueled.