Your basal metabolic rate (BMR) is the key to understanding weight loss. Unfortunately, it’s the one area researchers understand the least. BMR is the energy needed by your body to survive and for your lungs to breath, your heart to beat, your liver to cleanse, your brain to think, and your cells to divide and repair themselves. Every second of every hour of every day while awake or sleeping, your body is at work. So how do you find out what your BMR is? Type, BMR, in any internet search engine and you will get an array of explanations and calculators. The calculator will ask for your weight, height, age and sex. Some may ask for your body fat percentage, etc. These calculators are just a guess. The only way to determine your true BMR is to undergo an overnight study in a metabolic chamber, known as a whole room calorimeter. An excellent article was written by Jullia Belluz, for those who want to delve deeper into metabolic chamber testing. Problem is, there are not many of these facilities around. Most are for clinical research and not available to the general public. But there are other ways to more accurately determine your BMR.    The second most accurate way is indirect calorimetry. This is performed by laying down and relaxing while breathing into a handheld device for about 5 or 10 minutes. Any office that specializes in weight loss should offer this powerful tool to precisely assess your BMR.

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There are multiple studies that show extreme differences in the calculated BMR, and a person’s actual BMR’s obtained through Metabolic chamber, or indirect calorimetry. Some have over-estimated by as much as 30%. Let me illustrate the importance of this with an everyday example. You are a 6 foot, 200 pound, 50-year-old man. You plug in your numbers from a website BMR calculator and get a BMR of about 1898 kcal per day. Is this correct? That’s the problem, because as noted above, there are many different formulas to calculate BMR. Which one should be used? 

 

          Harris-Benedict equation = 66 +( 6.2 × weight in pounds )+( 12.7 × height in inches ) - ( 6.76 ×                                                                       age in years)

          BMR =1,882

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          Mifflin-St. Jeor = (10 x weight (kg)) + (6.25 x height (cm)) – (5 x age (years) + 5)       

          BMR = 1,780

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          Katch-Mcardle formula = 370 + (21.6 x Lean Body Mass(kg)) {Lean Body Mass = (Weight(kg) x                                                                         (100-(Body Fat)))/100 }

          BMR = 1,925

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The last formula is even more difficult to use because you must calculate your body fat percentage. Estimating your body fat is no easy task. There are 4 ways to determine body fat scientifically. The gold standard is hydro densitometry testing. This involves submersing your body in water and determining water displacement. Some scales can pass an electrical current to determine body fat, unfortunately, not very accurate. Skin calipers are another commonly used method. This method is very operator dependent. Again, more variability.

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These three different formulas gave three different results. In our example, the BMR ranged from 1780 kcal to 1925 kcal. That’s a difference of about 145 Cal. That may not sound like a lot but, if you overestimated your BMR by 145 Cal a day, you could gain 1 lb in about 23 days. Therefore, one reason you may have not been losing weight could be the miscalculation of your BMR. 

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EASIER TO DECREASE YOUR BMR HARDER TO INCREASE
 

Researchers don’t know why people have different metabolic rates. A couple of findings hold true. Genetics seem to play a major role. Men usually have higher BMR’s than women. BMR’s usually decrease with age, and about the only thing you can do to increase your metabolic rate is increase your lean muscle mass. Caffeine, green tea, chili peppers may increase your BMR slightly but not enough to be significant. Pills that claim to increase your metabolism are a waste of money and time.  

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Although there is not a whole lot you can do to speed up your metabolism, slowing it down is easy. That is one reason why it is easier to gain weight than lose it. Fasting and Crash diets are one way the body slows down it’s BMR. This may have been an evolutionary safeguard. Thousands of years ago, when there were no fast food stores right around the corner, and the next meal could be days or weeks away, the body compensated for these lean times by slowing down its BMR to conserve calories thus preventing weight loss. Other things that can slow your BMR and make it easier to gain weight are sedentary lifestyles, low protein diets, lack of sleep, and increased sugar consumption. Since your BMR is where the large majority of calories are utilized, and is the cornerstone of any weight loss plan, it’s important to know as precisely as possible.

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Thermogenesis, the digesting of food, also accounts for some burning of calories. Every time you eat, your body uses calories to digest and absorb your food. Some types of food require more calories for this process than others. For example, meals rich in protein use more calories than fatty meals. This process accounts for about 10% of your daily calorie requirement. So this, and your BMR, are pretty much out of your control and has nothing to do with your activity level.                  

 

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DETERMINING PHYSICAL ACTIVITY LEVEL 
 

Now let’s discuss the third and final piece of your Total Daily Energy Expenditure which is your daily physical activity. TDEE is equal to the BMR plus thermogenesis plus daily physical activity. Of the TDEE, roughly 20% is used during your day to day physical activity. This is the most variable determination in daily calorie expenditure. Assessment of physical activity is highly subjective, with most people overestimating their daily activity level. Let’s face it, who wants to say sedentary lifestyle? The typical calculated calories burned in a day will depend on your weight, age and sex. The formulas will also ask to determine how physically “active” you are and range from sedentary, light, moderate, active to highly active. Using our 200 pound, 50 year old male, he would burn 1,976 Cal by using a sedentary activity level verses 3,114 Cal if he used a very active lifestyle for his activity level. If you decide to use a calorie calculator like this, it’s better to underestimate your activity level than overestimate it.  A better way would be to buy a accelerometer, such as Fitbit, which does a pretty good job estimating your daily activity level. It can, through proprietary algorhythms, roughly determine your daily calorie expenditure. They’ve done studies and it’s not perfect but probably the best you can get without using calorimetry or radioactive labeled water.

 

 

EXERCISE NOT THAT IMPORTANT IN WEIGHT LOSS

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Exercise is important for many reasons, but the simple truth is, it accounts for very little in the big picture for weight loss. If you walk briskly at 4 miles an hour, for 30 minutes, depending on your weight, that 30 minute exercise session will be negated by an apple or 2 hard boiled eggs, or a protein bar or a glass of soda. The take home message is this, exercise for all the health benefits your body will derive from it, not to lose weight. The single most important factor, by far, to lose weight is your caloric intake.

 

So how many calories must you burn to lose weight? That depends on how quickly you want to lose it. A rough estimate to get you into the ball park is 500 Cal a day or 3,500 Cal per week to lose a pound a week. This was derived back in the 1950’s. The rational goes like this. A pound equals 454 grams. Fat contains 9 Cals per gram or 4,086 Cal, but most human body fat is made up of other substances and the fat composition is closer to about 85%, or about 3,500Cal. So, 500 Cal per day for 7 days, or 3,500 Cals per week. Recent research has shown this formula to hold true only in the early phases of diet and as time goes on the number of calories needed to lose a pound per week actually increase. This is why patients’ best results happen early on in their diets, often hitting the infamous plateau where each pound of weight loss becomes harder and harder as they lose more weight.

 

Counting calories is absolutely necessary! Anything you read that tells you differently is setting you up for failure. The biggest problem with counting calories is, most of us underestimate our daily caloric intake. Smart phones make it easier than ever to do this, but it will still be necessary to keep a calorie diary. Use this when you eat out to track everything you eat while you are away from home. You may think you can remember all the meals and snacks you eat while you are out, but you will forget. If you cook at home, you will also need to get a digital scale to weigh your portions and calculate calories. Counting calories is a pain, but it’s a good exercise for you to learn about portion sizes and to get a better understanding about what calories are in the foods you are consuming to fuel your body. After about a month or two, you won’t need your smart phone app or scale to calculate your daily total caloric intake.  You’ll know a majority of meals you’ll be eating, and their caloric values.    

 

Sometimes people need a little help or a “little jump start”, to get their diet headed in the right direction.  That’s where medical therapy can help. I personally, don’t like prescribing weight loss medication. I would much rather see patients lose weight with diet, exercise and life style changes, but giving the choice of obesity without meds or healthy weight with meds, I’ll pick the latter every time​​.