Active Metabolic Rate – How Many Calories Do We Need? (Feb. 18, 2010)

You here it on The Biggest Loser, it’s all about the science: Calories in versus Calories out.

I’ve started changing my lifestyle in 2008, really paying attention to what I eat and getting back on track with exercise. A healthy lifestyle is sometimes a tricky balance to maintain, but it is possible! Lots of people do it, and I want to be one of those! I did really well for about a year, then last fall, I hit a plateau and haven’t been able to break it. I was exercising 4-6 days per week and limiting my calories to 1200-1550 calories each day. Apparently, that wasn’t enough. That’s right, I actually wasn’t eating enough calories and my body kicked into a conservation mode, trying to maintain my weight versus shedding pounds. I recalculated my metabolic rates and realized I needed to increase my calories by several hundred calories daily!

So, what’s the science? The Basic Metabolic Rate (BMR) is how many calories you need for your height/weight/age just to survive in normal life. Then you have to adjust for your activity level, which is your Active Metabolic Rate.

For women, your BMR = 655 + (4.35 x weight in lbs.) + (4.7 x height in inches) – (4.7 x age in years).

For men, your BMR = 66 + (6.23 x weight in lbs.) + (12.7 x height in inches) – (6.8 x age in years).

As your weight and age changes, you’ll need to adjust your caloric intake.

Activity levels range from Sedentary (little to no activity) to Extra Active (very hard exercise 6-7 days per week).

To MAINTAIN your current weight, calculate using the following formulas to figure out your Active Metabolic Rate:
Sedentary (Little or no exercise): BMR x 1.2 = AMR
Lightly Active (light; 1-3 days per week): BMR x 1.375 = AMR
Moderately Active (moderate; 3-5 days per week): BMR x 1.55 = AMR
Very Active (hard exercise; 6-7 days per week): BMR x 1.725 = AMR
Extra Active (very hard exercise; 6-7 days per week): BMR x 1.9 = AMR

To LOSE Weight (at a healthy rate of about 1 lb. per week), take your AMR and subtract 500 calories. This is the science that when your calories out is more than your calories in, you will lose weight.

It’s working for me! I increased my calories and actually lost weight and inches! (Sorry, not revealing numbers.)

Also, just a reminder to make sure your calories are coming from the right places. The FDA recommends 55% of your calories coming from carbohydrates, 15% coming from protein, and 30% coming from good fats. Remember, Carbohydrates and Protein yield 4 calories for every 1 gram consumed, while fat yields 9 calories for every 1 gram consumed. If you need help with all of this, check out http://www.sparkpeople.com for a free online tracking tool. You may need to adjust your calories manually instead of going with their recommendations. Mayo Clinic came out with a study a couple years ago that showed people who keep a food diary are more successful at reaching their weight goals. Personally, I know I maintain and lose better when I’m tracking what I eat, then when I’m just guessing.

Let’s do a quick run down as an example:

Let’s say you have a 130 lb. woman who is 5′ 6″ tall and 25 years old.
BMR = 655 + (4.35 x 130) + (4.7 x 66) – (4.7 x 25)
BMR = 655 + (565.5) + (310.2) – (117.5)
BMR = 1413

If she’s lightly active, BMR * 1.375 = AMR of 1943
If she’s moderately active, BMR * 1.55 = AMR of 2190

Now, if she likes her weight and activity level, she should eat between 1943 and 2190 calories each day. But if she wants to lose weight and stay at the same activity level, she should reduce her intake by 500 calories each day, which means she’d eat between 1443 and 1690 calories each day.

Assuming she wants to lose weight, her calories should come from the following categories:

Carbohydrates = 55% of AMR = 794 calories (198 grams) to 930 calories (232 grams)
Protein = 15 % of AMR = 216 calories (54 grams) to 254 calories (63 grams)
Fat = 30% of AMR = 433 calories (48 grams) to 507 calories (56 grams)

I know this is a lot of numbers, but I do hope it’s helpful. Please be sure to verify any medical information with your doctor. Every one is different, but this is a good calculation for generic purposes.
Also, remember a healthy lifestyle = healthy eating + exercise + water + sleep! Happy, healthy day to you!

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