My husband's still trying to lose weight, and we got into a discussion the other day about plateaus and how people's bodies are different. I explained BMI and BMR and calorie needs for people of different heights, ages, weights, etc.

When it got to BMR and daily calorie needs, I found a calculator online and put in my info: 5 feet, 8.5 inches tall, 29 years old, 140. My BMR came out to 1,450. Then I went to the "caloric needs" calculator, which said to multiply my BMR by 1.55 for moderately active (exercise/sports 3-5 days a week - I work out 5 days a week, 40-45 minutes on average). It came out to 2,247.

Then I got stuck trying to explain. If I need 2,247 calories to MAINTAIN my weight at my current age, weight and activity level, and I'm eating 1,700-1,800 and working out like crazy, why am I NOT losing weight anymore.

Don't get me wrong, I don't WANT to lose weight at all. Most people think I look sick and too thin as it is. It's just got me stuck trying to explain to my husband how the whole thing works when, by calculations, I should still be losing and I'm (thankfully) not.

Because our bodies are not machines and the calorie needs of the formerly obese are less than the calories needs of someone who has not been obese.

What midwife said. Plus even without those factors, no generalized calculation is going to be correct for an individual. They are all gestimates and "your mileage may vary."

For example, at my current weight (which is higher than what's on the left here) the Freedieting.com calculator says I should maintain at around 1800-1900 calories. Well, guess what, I gain slowly at that level.

What I want is a way to increase my metabolism! And I don't mean by working out hours per day.

Jay

Online calculators are based on averages. The only way to know your BMR and calorie needs for sure is to have metabolic testing done by a professional. It's the same with BMI -- a person who never exercises and has 50% body fat could have the same BMI as a person who is a professional body builder with 5% body fat, because all that it takes into account is weight and height and it is based on population averages.

So while *on average* a person of your height and weight and activity level may have those numbers, that doesn't mean that you in particular necessarily do. If we took a sample of five people who were the same weight and height, and found that the levels of calories they needed to maintain their weight were 1200, 1800, 1500, 2200, and 3000, we could say, "The average number of calories needed to maintain this weight at this height is 1940," and it would be totally true, but not very useful.

Plus those formulas ask you how much EXERCISE you do, not how much activity you do in your normal life. I would say for the vast majority what you described would not maintain on "moderately active" with that amount of exercise. Most of us dont burn enough in our normal activity.

In fact a recent study showed that sitting for extended periods (like a desk job or watching TV) actually changed the enzymes in our body resulting in a significantly reduced metabolism vs. our own normal metabolism. Our body can go into mini hibernation very very quickly.

If those formulas were developed early in the 20th century like Bright Angel said, they are totally off for our current lifestyles. I personally am much closer to "sedentary" + exercise than "very active", even though the description reads very active.

I am a huge Little House on the Prairie fan. I have the LIW cookbook. In it she describes what Almanzo ate for breakfast for a day on the farm. It was a quantity of food that is just astounding . And yet he was very thin in all the pictures. Lifestyle then vs. lifestyle now.

I do zero activity at work...desk job. My HRM says in a 40-45 minute workout I generally burn no fewer than 450 calories...

Guess I'm just lucky for now...

An additional comment for clarification.
One's BMR
is the calculation for the amount of calories one burns when one's body is totally at rest.
It does NOT involve one's activity or exercise.
One's BMR is multiplied by an activity factor percentage to determine how it is affected by the body's movement.

yes, but I think the definitions of the activity factors are what are drastically overstated.

"moderately active" is pretty far off from what they used to be. Someone who sits at a desk job all day and then hits the gym is still FAR more sedentary than your average housewife in the days before washers and dryers and dishwashers. Yet 1920's housewife would probably be listed as "sedentary" for the multiplication factor.

But the other thing I was stating is that there are new studies that suggest that the BMR - the totally at rest metabolism will actually decrease in a person who is sitting or resting for long periods of time, vs. the BMR of the SAME person at rest in a day of periodic low level activity. Even just standing at your job, vs. sitting at your job may affect how many calories you burn when you take your sleep.

One very important factor is age & sex.
I was at a demo of infra-red photography (where the temperature is photographed)...In family pictures the mothers were very often noticabely cooler than the teenage children. Especially big difference was between young men and their mothers. Eyeopener for me... you can actually SEE some peoples lower metabolism, they literally radiate less heat.