BMR!? Confused!

lwagnitz

So, my BMR is 1,600 calories. I set MFP goal to lose 1lb a week. I didn't put any exercise (sedentary).. and can't really exercise because of an injury, anyway. But, it's telling me to eat 1,520 calories. Don't you need to burn 3,500 calories to shed a pound? I'm only losing 80 calories a day, so that's 560 calories a week... no even a 1/6th of a pound. I'm confused... help?

0somuchbetter0

Your BMR is the number of calories your body needs just to survive -- breathing, pumping blood, etc. Like if you were literally lying in bed all day and doing nothing else. Your TDEE (Total Daily Energy Expended) is the number of calories to burn doing stuff -- working, going grocery shopping, cooking, etc. Ideally, once you figure out your TDEE, you should eat about 20% less than that to lose at a healthy rate.

McLifterPants

Your BMR, or Basal Metabolic Rate, is what a doctor would feed you if you were in a coma to keep your organs functioning. What your body actually USES in a day is your TDEE, or Total Daily Energy Expenditure, and that is the number that your cut comes from. There are many TDEE calculators online, but I like this one: http://www.fitnessfrog.com/calculators/tdee-calculator.html

omma_to_3

Sedentary TDEE is usually calculated as BMR*1.2 so for you, it would be 1920. Your 1520 calories gives you a daily deficit of 400 calories without exercise, so about .8 lbs. per week.

lwagnitz

I thought you weren't supposed to go under your BMR though? That's what I'm confused about, too.

omma_to_3

I thought you weren't supposed to go under your BMR though? That's what I'm confused about, too.

That's said by many MFPers with no scientific evidence to back it up (at least not that I've ever seen). What they should be saying is that you don't NEED to. You can lose weight by eating at your BMR, you'll just be losing at a slightly lower pace. There is a number you shouldn't go below, but that's very individual. The medical community says 1200, but 1200 for me, being a woman of 5'4" is FAR different than for a man of say 6'. I personally net 1200 (meaning I eat all my exercise calories back). Most days I'm eating around 1650 calories to net 1200. Even at netting 1200, my projected weekly weight loss is 1.3 lbs. and my actual is usually .8 to 1 lb.

geekyjock76

For women, the lower net limit can be determined using this formula:

30 kcal x lean body mass in kg x 5 days

This estimates the threshold at which, if crossed and maintained for 5 consecutive days, may lead to disruption in LH pulsatility and ovarian function. It isn't an "all-or-nothing" estimate, however. What that means, is disruption does not occur at or above the number. With that said, every woman will have a different threshold.

Example: 130 lb woman with lean body mass of 100 lbs (45.45kg)
30 kcal x 45.45 x 5 days=6818 net calories over a 5 day period

BMR=1351 Activity Level: Moderate (1.55) TDEE=2095
Deficit: -300 from food/-200 from daily exercise=500
Eats=1795 calories Nets=1595
1595 x 5 days = 7975

7975 > 6818

So, theoretically speaking, she would have a value of 1157 calories above threshold while assuming a 500 calorie daily deficit from a combination of food restriction and exercise. Thus, she can cut another 232 calories each day (732 calorie sum deficit) until she crosses the threshold.

For more on this read the research:
http://jcem.endojournals.org/content/88/1/297.full

lwagnitz

Ahhh, me gets it now. :)Thanks for the insight!!

davert123

I thought you weren't supposed to go under your BMR though? That's what I'm confused about, too.

That's said by many MFPers with no scientific evidence to back it up (at least not that I've ever seen). What they should be saying is that you don't NEED to. You can lose weight by eating at your BMR, you'll just be losing at a slightly lower pace. There is a number you shouldn't go below, but that's very individual. The medical community says 1200, but 1200 for me, being a woman of 5'4" is FAR different than for a man of say 6'. I personally net 1200 (meaning I eat all my exercise calories back). Most days I'm eating around 1650 calories to net 1200. Even at netting 1200, my projected weekly weight loss is 1.3 lbs. and my actual is usually .8 to 1 lb.

^^^^^^^^^^^^^^^^^This is right. The 1200 (1400 for men) figure is a bottom line minimum and if you do this you need to eat very healthy. it is the minimum you can get away with to get all the nutrients your body needs IF you ear decent food. Beware though if you do start doing a lot of exercise you will need to eat more. Just my experience - I start getting colds and minor illnesses as well as start to feel completely knackered if I over do it . I am trusting MFP calcs at the moment and they working very well for me