BMR - Confused.......

katie_w_84 · October 2012

Hi All....

I am really confused with everyone talking about BMR and not eating under this..... not anything I have ever thought about!

I have just taken a look and based on my height/weight/age (5ft11, 80kg and 28yrs) it says by BMR is around 1,6400. Does this mean I should be eating that many calories daily even after exercise? or that I shouldnt ever go below this (ignoring if exercise burns more)......

Very confused and hoping someone can shed some light for me ;-)

omma_to_3 · October 2012

There isn't any scientific evidence that I've ever seen saying you can't eat below your BMR. People here talk about it all the time, but none have ever shown me evidence. I aim to net 1200 calories, after exercise. It works for me, and is low enough that I don't stress if I go over a bit.

teez52 · October 2012

If your BMR is at 1640 (I'm guessing you put an extra zero in your post since I'm going to assume that you are not a giant or professional athelete) that means if you calculate your TDEE at an activity factor of 1.2 you get

TDEE: 1968 Cal

Now, your BMR is what your body uses through a normal day if you did nothing but lay in bed. Your TDEE is what your body uses through a normal day with you moving around. I tend to stick with the lowest activity factor and then eat back my cardio calories. I personally do not track my calories burned through weightlifting since those are very difficult to actually track (some will argue that point, but it's what works for me). If you want to up your activity factor to say a 1.4 or 1.5 depending on your exercise plans, you would not want to eat back your calories from cardio since that would be counting those twice.

Now for a bit more math we know your TDEE is at 1968 and if we take the 20% rule your target calories per day would be:

1968(.8) = 1574.4

Now that would put you at just around 400 calorie deficit a day which would translate to 2800 calories per week which would put you at just under a pound of weightloss a week (given that a pound is 3500 calories). If you want, you can do a straight 500 calorie deficit which would put you at 3500 calories a week and thus give you 1 pound per week. That would look like:

1968 - 500 = 1468 calories per day.

Still confused? Feel free to send me a PM.

UsedToBeHusky · October 2012

It depends.

What are your goals?
How much do you want to lose?
How long have you been eating below BMR?

Where you are at in your journey determines whether or not you can eat below BMR. The body needs fat and to avoid using too much of it, will resort to using muscle for energy as well. Muscle burns more calories than fat so losing muscle will cause you to burn less calories over time. The morbidly obese with 100+ or more to lose can generally eat below BMR and lose extremely well. Because they carry more weight than is natural for their frame, they have more muscle to start with. However, when you eat below your BMR you are depriving yourself of proper nutrition. Your body's required macronutrient levels(carbs, protein, fats) and micronutrient levels (calcium, magnesium, potassium, vitamins) can not be met without eating at BMR. This means that you become malnourished. Long periods of malnourishment cause a hormonal reaction in the body that will impede weight loss. Along with hormone issues, the body will resist using up its fat stores and will draw upon muscle for energy instead. Muscle is more active than fat metabolically so losing muscle will mean that your body burns less calories. So... while you can get away with eating below BMR for a period of time, eventually, you will have to eat more calories (and lift weights to maintain muscle) to progress.

You and I are roughly the same height, however, I can tell that I weigh more than you because my BMR is around 200 calories more. For the first 8 months, I ate below BMR and lost 75 lbs. But then weight loss slowed down, so I had to change gears. I began eating at a 300 calories below my TDEE (total daily energy expenditure) and began lifting weights. I have been doing that for the last 9 months. I have only lost 10 lbs but I have lost more in inches than I had eating below BMR. I am leaner and stronger now. I am burning more body fat.

To summarize, if you want to shed a few pounds quickly, and are not concerned with losing muscle (such as individuals who are morbidly obese), then eating below BMR for a short period of time is an acceptable method. But if you do not have 50+ lbs to lose, then you do not have the muscle to spare, and eating below BMR will not help you to accomplish your goals.

Hope this clarified things for you.

katie_w_84 · October 2012

Ok, so if I read that correctly I should be eating around 1,468 calories a day and I DON'T want to "eat back any calories"? (I dont really ever quite agree with the people who strongly agree or disagree with the eating back idea as surely it is all maths...... you lose weight if you burn off more than you intake... but you dont want to intake too few calories or it can impact your metabolism etc in the long run..)

To me, 1,400-1,600 seems like a healthy intake that is sustainable for life and added to that 6 days a week of weights and/or interval training that are ignored as part of any calorie tracking.....

Hopefully this is what you meant? otherise I am going to have to PM you! ;-)

teez52 · October 2012

Ok, so if I read that correctly I should be eating around 1,468 calories a day and I DON'T want to "eat back any calories"? (I dont really ever quite agree with the people who strongly agree or disagree with the eating back idea as surely it is all maths...... you lose weight if you burn off more than you intake... but you dont want to intake too few calories or it can impact your metabolism etc in the long run..)

To me, 1,400-1,600 seems like a healthy intake that is sustainable for life and added to that 6 days a week of weights and/or interval training that are ignored as part of any calorie tracking.....

Hopefully this is what you meant? otherise I am going to have to PM you! ;-)

I would say start there around 1400-1500 and eat back your cardio calories. To show you the math, lets take a look here, we'll make it a story problem:

Katie eats an average of 1400 calories per day for a week. This means that she has eaten 9800 calories in those 7 days. Katie also runs 2 miles 6 days a week where she burns an average of 250 calories. For reference Katie currently has a BMR of 1640 and a TDEE of 1968 when calculated at a 1.2 activity factor that does not take into account exercise during that week. How many calories does Katie actually eat during a day?

So the math would work out like this:

1968 - 1400 = 568 calorie deficit every day before exercise
1400 - 250 = 1150 calories after cardio
1968 - 1150 = 818 calorie deficit

That in my opinion is too much of a deficit for someone with your stats, but I'm no expert. If you want to take into account weightlifting or crossfit or something that is not as easy to calculate the calories burned for you can always raise that activity factor up to 1.3 (2-3 days per week) or 1.4 (3 - 5 days per week) and then just subtract any cardio calories you have.

Feel free to PM me if you would like.

ashowers36 · October 2012

From what I understand if you eat under a certain number of calories (depending on age, weight, and height) you can actually put your body into starvation mode and make your metabolism worse, making it harder to get in shape. It can also be dangerous to your health in the long run. As for the calories you "gain back" by exercising, no you do not have to eat those back if you don't want to from my understanding. I also tried Weight Watchers for a while (didn't do it long as I am a picky eater and it made dieting very very much a pain) and even with that program you had a choice to eat back those calories or not. If you don't it will just expedite your weight loss goals a little bit. But you NEED to eat those original calories in your BMR.

cmriverside · October 2012

How this site works:

http://www.myfitnesspal.com/topics/show/186814-some-mfp-basics

http://www.myfitnesspal.com/topics/show/61706-guide-to-calorie-deficits

http://www.myfitnesspal.com/topics/show/10589-for-those-confused-or-questioning-eating-your-exercise-calories

In depth explanation of BMR TDEE etc.

In Place of a Road Map
http://www.myfitnesspal.com/topics/show/654536-in-place-of-a-road-map-2-0-revised-7-2-12

deksgrl · October 2012

BMR is what they would feed you in a coma to fuel your basic bodily functions. Why would it ever make sense to eat less than that, if you get up, move around, go to work or school, work out? If the doctors figure that is enough to keep me alive, I'm certainly not going to eat less than that.

dhein · October 2012

Figuring your BMR based on height weight and age is just an apporx. To determine your true resting rate you need to test. There are a few ways to do this - check with local health clubs and fitness centers for a device called BODY GEM. This will actually measure your oxygen gas exchange and give you a good idea of your true RMR. Working with most Weight Mgmt Dr and Nutritionist, they will tell you, for effective weight loss and effective change, you should not drop below 500 calories below your RMR (some not under 1200 calories unless under DR supervision - which ever no is lower). So tracking what you eat, wearing a heart rate monitor to help determine what you actually burned during a workout, knowing your RMR should get your results.
Depending on the type of exercise you are doing, (super intense every day like P90X, insanity etc) you may need to increase your calorie intake if you are burning more than 500 calories.

BMR - Confused.......

Replies

Categories