Scientific Way to Lose (or Gain) Weight: In Insight into Basal Metabolic Rate (BMR)
Scientific Way to Lose (or Gain) Weight: In Insight into Basal Metabolic Rate (BMR)
So, you want to lose weight! Most do! But you don’t want to follow fad diets known by many names; thousands of books have been written on the topic with enticing pictures of recipes, and yes, those ads that keep coming from nowhere when unknowingly your finger clicked on a link promising zillions of things about the magic weight loss! So, you fall prey to this billion-dollar industry and start trying few things! Well after six months you get sick with the regimented approach and you are back where you were!
what is the truth about weight loss or weight gain? In fact, both gain and loss go hand in hand, and surprisingly principal is the same. Let’s discuss this to get the facts so you can implement it at home with simple techniques. Please refer to my post on BMI to understand Basal Metabolic Rate (BMR) to start your weight management on the right footing.
Basal Metabolic Rate (BMR)
Suppose we don’t do anything one day; just sit, sleep or lie down all day on the couch doing nothing. We even don’t eat that day. We are still breathing, the heart is still pumping blood, and we are thinking things! All these processes consume energy, in other words calorie that we have come to know. This means that, for us to function properly, these essential body functions must go on at the expense of minimum energy needed for every day. This minimum energy (or calorie) needed is called BMR. We must have this minimum calorie, no matter what, for us to survive and function for day-to-day activities such as going to work, walking the dog or resting in the warm sandy beaches of Honolulu.
But how do I estimate my BMR in the comfort of my home as a starting point for my body type? Read on! As we all know, everybody’s metabolism is different! Some have big-frame body, others medium or small frame. This is dictated by characteristics that you inherited you’re your parents, grandparents, grand grandparents. And on top of that there are environmental and ethnic differences in world population.
Further, you may also have heard the term- fast metabolism or slow metabolism. This is a complicated topic and will not be discussed here but for now just remember this: A person with fast metabolism burns calorie at a faster rate than a person with slow metabolism. In other words, a person with fast metabolism can consume lots of food but not gain weight as opposed to a person with slow metabolism who eats less but still gains weight. This metabolism thing is also age-related. As you get older, your metabolism slows down and you are likely to gain weight. However, this can be controlled as will be discussed in my later posts.
All these affect BMR. Therefore, BMR varies among people even with the same weight, height and age! If you are a person with the same daily routine: wake up, eat something, go to work, come home, eat something, watch TV, go to bed! Repeat! Basically, a couch potato. Or you are an athlete, perform wait training, run, eat food that promotes health. You are ware of what is important to you. Active life style! BMR for both will be different.
Each person is unique even among siblings. So, your BMR is unique to you. From here, you can decide to be active for good reasons and understand what it will take to be healthy and happy!
Here is how to estimate your BMR
Estimating BMR at home
Based on Obesity journal publication scientists have developed equations (formula) for predicting BMR. Two formula are well researched and used today. They are:
· Mifflin-St Jeor formula
· Harris-Benedict formula
While other factors such as % body fat measurement may provide better outcome, these were not suitable for quick screening in a clinic or hospital for BMR estimation. Therefore, above two formulas don’t consider the body fat. So, Katch-McArdle developed another formula that considers % body fat in addition to weight, height, age. Also, Katch-McArdle formula is gender neutral. This formula is more accurate, and you can use this at home by measuring % body fat described in one of my posts.
All formulas are discussed below with an example. Measurement units are metric. Kilogram (kg) weight, and centimeter (cm) height can easily be converted into pounds and inches. I will use the following data as an example calculation and discuss interpretation of BMR numbers:
Example Data
· 140 lb = 63.5 kg
· 5 feet 3 inches= 160 cm
· Age = 52 years
· Body fat = 25% (measured by Waist-Hip Ratio).
Note: 25% Body fat represented in decimal = .25. This is another way of presenting % Body fat. Use decimal representation for Katch-McArdle Formula described later
Mifflin-St Jeor Formula
BMR (Kcalorie) Men: 10*weight (kg)+6.25*height(cm)–5*age(year)+5
Plug in numbers from the above example:
= 10*63.5+6.25*160-5*52+5
= 635+1000-260+5
= 1380
BMR for this man is 1380 kcal/day
BMR (Kcalorie) Women: 10*weight (kg)+6.25*height(cm)-5*age(year)-161 = kcal/day)
Plug in numbers from the above example:
= 10*63.5+6.25*160-5*52-161
= 635+1000-260-161
= 1214
BMR for this woman is 1214 kcal/day
Harris-Benedict formula (revised version):
BMR (Kcalorie) Men: 13.397*weight(kg)+4.799*height(cm)-5.677*age (year)+88.362
Plug in numbers from the above example:
= 13.39*63.5 + 4.799*160 - 5.667*52 + 88.362
= 850.265 + 767.84 - 294.684 + 88.362
= 1411.783
= 1412 (rounded)
BMR (Kcalorie) Women: 9.247*weight (kg) + 3.098*height (cm) - 4.33*age (year) + 447.593
Plug in numbers from the above example:
= 9.247*63.5+3.098*160-4.330*52+447.593
= 587.184+495.68-225.16+447.593
= 1305.298
= 1305 (rounded)
Katch-McArdle Formula (gender neutral)
BMR (Kcalorie): 370+21.6*(1-% body fat in decimal)*weight in Kg
Note: convert % into decimal. Example: 45% body fat = .45
Plug in numbers from the above example:
= 370+21.6*(1-0.45)*63.5
= 370+21.6*.55*63.5
= 370+754.38
= 1124.38
= 1124 (rounded)
Which formula to use?
The following Table summarizes the data from example used above. For the sake of convenience, example data are:
Weight, 63.5 kg; height, 160 cm; Age, 52 years; Body fat, 25 % or .25
Also consult my earlier post on calculating % Body fat
Based on this example and scientific literature, use Mifflin-St Jeor formula for BMR. If body fat percentage is known, use Katch-McArdle formula.
These calculations may be little challenging! Use this calculator for BMR that uses Mifflin-St Jeor formula. I have used metric units in the above example but calculator can take pounds for weight and inches for height input also.
Interpreting BMR
Now you know your BMR- the basic calorie that will be needed for your survival. If you are fat (based on BMI not BMR), and are eating the same way, you will never lose weight. If you are thin and are eating the same way, you will never gain weight. If you are fat and want to lose wait based on desirable BMI, you need to cutdown calories and start being active. Over a period of time, your BMR may change after you’ve achieved your healthy BMI range. Maintain that BMR level and continue habits that led to this BMR.
If you are thin or underweight, you need to eat more and perform some weight bearing exercises to bring your BMI in the desirable range. Once you have put few pounds and are in healthy range, your BMR will increase due to increase in muscle mass. Maintain that BMR.
You see, there is a complex relationship! The below Table explains where all these calories go. It is now clear that each person has different calorie need and calorie expenditure based on activity levels. Activity levels and calorie expenditure or balance is described well by United States Department of Agriculture (USDA).
Key Takeaways
· Know your BMR. It helps where you are and where you want to go! This is minimum amount of energy (calorie) needed to maintain vital body functions such as respiration and digestion
· About 70% to 80% of total energy goes for BMR, rest 20% to 30% for other things such as activities like biking
· Use Mifflin-St Jeor formula to calculate your BMR
· Use Katch-McArdle formula to calculate BMR if you are very active, athlete, and know your body fat
· There is a complex interplay of BMR, BMI and body fat. These can be manipulated to a desired level by nutrition and physical activities to maintain optimal health.