Knowing how many calories your body burns to sustain your current lifestyle BEFORE you begin to try and lose weight can be the key to your dietary success. Luckily it's pretty simple to figure out. The first step is to calculate your BMR.
What is BMR you ask?
BMR is short for Basal Metabolic Rate and that stands for the number of calories needed by your body JUST to keep it alive. Basically it's the number of calories you would need if you were in a COMA ... just lying there ... not getting up ... not talking ... not walking ... not getting dressed ... not even eating and DEFINITELY not exercising.
BMR does NOT represent your maintenance calories .... but it can be used to calculate them :)
There are several way to figure out your BMR. The most accurate unsuprisingly requires a trip to a doctor or specialist. Measurements are taken just after you awake in a darkened room after 8 hours sleep and 12 hours of fasting to make sure the digestive system is inactive while you are still in a reclining position in bed. Sounds like an awful lot of effort, and you're right, it is ... so we won't bother .... luckily for us there is a really good way to ESTIMATE what your BMR is using a fairly simple calculation which for our purposes is plenty accurate enough to calculate a rough maintenance calorie number.
Now there are plenty of good BMR calculators out there (google it) but if you are curious about the specific calculation used BY those calculators .... here it is. We'll do it long hand just for giggles.
English BMR Formula
Women:
BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
Men:
BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in years )
Metric BMR Formula
Women:
BMR = 655 + ( 9.6 x weight in kilos ) + ( 1.8 x height in cm ) - ( 4.7 x age in years )
Men:
BMR = 66 + ( 13.7 x weight in kilos ) + ( 5 x height in cm ) - ( 6.8 x age in years )
I live in Canada but I still like working in pounds for body weight so here goes.
I am a 52 year old woman. I am 5'5" tall or 65" and I currently weigh 220 pounds. Down from 325 ... stop laughing ... lets plug in those numbers, shall we?
BMR = 655 + (4.35 x 220) + (4.7 x 65) - (4.7 x 52)
BMR = 655 + 957 + 305.5 + 244.4
BMR = 1673.1
Ok then that means my body needs 1673.1 calories a day just to stay alive, keep my heart beating and lungs working, digesting food, processing waste ... you get the picture
NOW if were to start moving about, getting out of bed, going downstairs to make breakfast, walking the dog, getting the paper, vacuuming etc I would need MORE calories to sustain my weight ... how many more depends on how active I am in any given day.
Lucky for us there is ANOTHER formula, (this one is easier) to calculate THAT number, which represents maintenance calories.
Let's say, just for argument I live a really sedentary life. I don't get out much. I sit most of the day either at a desk or on a couch. I do a little light housework but I don't do any outside sports, yard work or much of anything else ... to calculate my MAINTENANCE calories to support that sedentary lifestyle I would take my BMR number and multiply it by 1.2
BMR x 1.2 (for sedentary) = MAINTENANCE CALORIES
1673.1 x 1.2 = 2007.72
So there we have it. If I live a sedentary life I could eat roughly 2007 calories and still MAINTAIN my current weight of 220. If I am more active than sedentary I would use a different factor to multiply my BMR by:
| Activity Factor | Category | Definition |
|---|
| 1.2 | Sedentary | Little or no exercise and desk job |
| 1.375 | Lightly Active | Light exercise or sports 1-3 days a week |
| 1.55 | Moderately Active | Moderate exercise or sports 3-5 days a week |
| 1.725 | Very Active | Hard exercise or sports 6-7 days a week |
| 1.9 | Extremely Active | Hard daily exercise or sports and physical job |
So you see ... the more you move, the more you can eat and not gain any weight.
BUT .... you want to LOSE weight
Well now that you know your maintenance calories it's pretty simple to figure out the deficit you should aim for. There is just a little more math to do, bear with me it's not too hard.
A pound of fat can be represented as 3500 calories ... if we were to eat 3500 calories LESS in a day than our maintenance calories we'd lose a pound a day .. but that is NOT a reasonable number. A much healthier number to aim for is, at the MOST about 1% of your current weight or 1-2 pounds a week in general, although very obese people can lose at a slightly higher rate.
This works out kind of neat actually ... remember that a pound is 3500 calories? Well there are 7 days in a week and that divides quite nicely into 3500, soooo if you were to shave 500 calories a DAY off of your maintenance calorie number, you would, over the course of a week eat 3500 calories less than your maintenance or 1 Pound's worth of fat ...
Since my maintenance calories at sedentary worked out to 2007 if i were to subtract 500 from that and eat 1507 calories a day I could expect to lose 1 pound a week. If I wanted to lose 2 pounds I would have to take ANOTHER 500 off daily for 1007 calories ... (see below)
Now another word of caution. To maintain a healthy weight loss and to give you the best shot at KEEPING the weight off it is not advisable to eat less than 1200 calories (for a woman) and 1500 (for a man) it's just not healthy to aim for more, that puts the 1007 calories/day right out of the picture so in reality it is just not feasable for me to aim for a 2 pound a week loss with a sedentary lifestyle ... it would be impossible to make sure you got enough minerals and nutrients eating that few calories on a daily basis ...it just isn't healthy, so don't do it. Period.
Besides, eating too few calories can actually SABOTAGE your progress and/or cause you to lose muscle mass INSTEAD of fat and that is not a good thing. It sends you body into what is commonly called starvation mode and that causes all kinds of havoc with your system and metabolism. It's not worth it .. I repeat .... don't do it. Make sure you are eating ENOUGH to lose weight .. it sounds counter intuitive but it works ... trust me.
My general goal is to eat 1500 calories a day, give or take. That should net me a loss of a pound a week or maybe more if I am more active than sedentary. I find 1500 calories allows me to eat three decent meals a day with room for snacks and/or dessert. I am not deprived in any way and I can enjoy the occasional meal out without any difficulty.
Hopefully this might help you figure out your own numbers. Knowledge is power. Armed with the right numbers, you should not have any difficulty meeting your goals and I wish you luck on your journey.