Chapter 2 Obesity: The Basics of Your Metabolism

Chapter 2: Obesity – The Basics on Your Metabolism

Human metabolism is complex but there are basic truths that apply to all of us. Dramatic changes in metabolism are rarely the root cause of obesity in humans.


In the last few months, I have heard all these statements from patients. Over the last 20 years, I have heard them over and over again.

“I hardly eat anything and still can’t lose weight”

“I eat much less than my husband and he is 300 pounds” (from a 175 female)

“I was on Weight Watchers for 12 weeks and didn’t lose a pound”.

“I know what I eat and heard all this stuff before. I want to know the real reason I can’t lose weight”.

“My metabolism is very slow. I can eat less than 1000 calories a day and still gain weight”.

“I know my thyroid tests are normal but there has to be an explanation for why I can’t lose weight”.

It isn’t easy to lose weight. Obviously, if losing weight was easy, we wouldn’t have the huge problem with obesity that we have in this country. And because it is difficult to accomplish, we have all the hype surrounding weight loss. There are plenty of opportunities for people purchase the new “solution” or “miracle” in weight loss management. I am very empathetic to the difficulties of losing weight and the medical, social, psychological, and economic consequences obesity can have for people. I admit, however, that I get frustrated with the shortcuts that people want to take to deal with this important problem.

As an Endocrinologist, I have treated hundreds of patients with diabetes over the years. When a person develops diabetes, we strive to help that individual acquire the knowledge and skills necessary for them to become effective in self-management or their disease. Estimates vary, but most experts agree that the time required to provide just basic instruction (so-called survival skills) to a patient with newly diagnosed diabetes is between 15-20 hours. There is then a need for additional learning and support as the patient embarks on a new life with diabetes, facing new issues and circumstances sometimes on a daily basis. Guidance from trained health professionals, learning, and self-management are lifelong requirements of good diabetes care.

The first session in diabetes education is usally “What is diabetes?” Very basic information is provided about how insulin works in the body, why the blood sugar goes up. In short, it is necessary for the person with diabetes to understand some concepts about human physiology. Time to go to school again and learn some facts about how the body works.

The approach I have taken toward obesity is much the same. The individual with a weight problem has to go back to school and learn some basic physiology. How does the body store energy? What determines our metabolic rate? What is obesity? How did this happen to me?

Yes, human physiology is complex but there are some basic principles that anyone can understand and apply. In fact, many of my patients with diabetes have become experts with knowledge and skills far beyond mine when it comes to applying what they have learned through experience with their disease. I recall three teenagers with diabetes that wanted to compete in the triathlon. There are different types of triathlons but the type they were interested in was an Ironman triathon. The Ironman is a 2.4-mile swim, 112-mile bike ride and 26.2-mile run. Seems impossible, doesn’t it. These boys started training together and would carefully monitor their blood sugars, calories consumed, insulin taken and report to me the results. They figured out, among many things, how long they could bike without extra food and how much insulin to take prior to workouts. They taught me how that kind of training effected diabetes management. Besides that, those kids were incredibly inspiring!

Likewise, many of individuals I have helped to lose weight over the years have learned a great deal and can share those learning with me and other individuals trying to master the problem. That is one of the reasons group visits or sessions are so beneficial in the management of chronic conditions like diabetes and obesity. It provides the opportunity for people to learn from each other.

The point is that weight management starts with the basics. Apply the basic principles regarding metabolism. You can then develop your Calorie Equation. This is where it all must start. If you are unwilling to learn these basic principles or refuse to believe them, forget about losing weight. You may lose a few pounds in the short term but you wouldn’t keep it off. You will be setting yourself up for yet one more diet failure. Learn these principles and apply them and you will be laying the groundwork for lifelong weight control.

In the simpliest terms, if you are maintaining your weight, the energy equation can be written as:

Energy in = Energy out

At energy balance, energy intake must equal energy expenditure. For you physic buffs, this is so because human metabolism must adhere to the the first law of thermodynamics, like the rest of nature. That law states that energy is neither created nor destroyed.

The “Calorie”, of course, is the measure of energy expenditure we use in the field of human metabolism. It is technically a unit of heat. For our purposes, the exact definition is not important and I will be using the big C – Calorie and small c –calorie interchangeably in this blog. Again, physics buffs know the different but how many physics buffs are there anyway?

So at weight maintenance, we can rewrite the equation as follows:

Calorie in = Calories out

To lose weight, one must consume fewer calories and/or use more calories through physical activity than are required to maintain that weight. In other words, if you are maintaining your weight, you have an equation that is in balance.

Current Weight (W) = Food (F) calories - Calories burned with
Activities (A)
OR

W = F – A

In other words, if you want to lose weight, you have to consume less food or be more active. Da!! I’m sure you have heard this before but the truth of this equation doesn’t “grab” you. How do I make this equation “actionable”, something you can apply to your weight loss and maintenance plan and use on a daily basis?

In order to develop a few rules that you can trust and then use them to help you lose weight, I have to explain a few principles that will be, at first, a little complicated. We have to dig deeper and learn the facts about our metabolism.

In many books, there is a mystique created around the word metabolism. Just think of all the products that boost that they can speed up your metabolism. Some go so far as they claim they specifically burn fat, or can help you lose weight while you sleep. The latter claim really isn’t that bad since, unless you are dead, you are still burning calories during sleep. So everyone is “losing weight” while they sleep. However, to claim you can lose more during sleep through some artificial means of accelerating your metabolism is a stretch for most of these products. There are a few substances that do speed up the metabolism and we will get to them later in this blog.

Let’s start with a few definitions.

Total energy expenditure (TEE) is the total amount of energy expended in a 24-hour period.

Basal metabolic rate (BMR) is energy expended to maintain vital functions (keep you alive).

Resting energy expenditure (REE) is the energy consumed by a resting individual after an overnight fast in a comfortable environment.

Thermic effect of food (TEF) also called diet –induced thermogenesis is the energy expended to metabolize a meal.

Activity expenditure is the energy expended with any activity or exercise.

Let’s expand on these definitions. Basal metabolic rate (BMR) or basal energy expenditure (BEE) is, as the definition implies, the amount of energy needed to keep you alive with all body parts working. It is not practical to measure and has been replaced by RMR. They aren’t the same. REE is measured after the person wakes up, usually after going to the lab and resting there for 30 minutes or so, prior to the measurement. Because of the extra activity, REE is going to be about 10% higher than BEE. REE accounts for about 70% of our energy expenditure.

TEF is a reflection of the energy consumed during metabolism of foods. One can think of it as the energy required to absorb the food, move it around the body, transform it to into energy or convert it to a form that can be stored for later use. It should make sense that there is an energy cost to digesting and storing food within the body.

For example, we can’t ingest 100 calories of food and put 100 calories in storage within the body. There is a cost in energy from your mouth to the storage site within the body. This is a complicated area of metabolism since the energy cost for carbohydrates, fats, and proteins differ. Furthermore, the TEF differs under conditions of underfeeding, overfeeding, stress, or illness. However, TEF is considered to contribute only approximately 5-10% of TEE. Since this is a relatively small part of TEE, the variables associated with composition of the diet and situation are not going to play a major role in your response to calorie restriction or success in achieving a more ideal weight.

Activity simply refers to the amount of energy expended with activity that we will cover in an exercise posting . This is the second largest component of the TEE and is the most variable. As I will point out later, the variability is not just related to whether or not you are avid exerciser or not. Activity energy expenditure also takes into account spontaneous body movements like fidgeting, moving your arms when you talk, etc.
As you study groups of individuals, this spontaneous activity can account for 100 to 800 calories of energy expenditure a day. I will tell you more about this when I tell you about the “fidgeting diet” later..

The chart below shows you graphically the components of TEE.

Now, no one can be at their REE all day long. You have got to get up and move about in this world to get your work and play done. For our purposes here, it is a fair approximation that the usual sedentary American will need about 1.3 times REE to maintain his or her weight at that sedentary lifestyle. This is important so let me highlight it.


Weight maitenance = REE x 1.3


This includes the calories burned with the usual 8 to 5 desk job and all the morning preparation of getting ready for work, getting to work and back, and spending most of the evening on the couch prior to bedtime.

So in summary, we have TEE = REE + TEF + Activity.

In the sedentary adult, the REE is the major contributor, and predictor, of how many calories you need to maintain your weight. When measured, it sums the energy expenditure from the entire body. Thinking in broad terms, we are a combination fat mass and fat-free mass making up the two major “compartments” in our body. The fat mass is what we would like to keep under control. Some of us are 15-20% fat. Others, with weight problems, can be 40-50% fat. Fat tissue is not as metabolically active as fat-free tissue, such as muscle and your organs. In fact, organs are many times more metabolically active than muscle when you are at rest. It makes sense, therefore, that, as you become proportionally fatter as a percent of body weight that your metabolic rate will be lower per a representative pound of you than someone who is leaner. In other words, your REE may be lower per pound than a leaner fit individual.

Can you measure energy expenditure? Of course, we can, but until recently it was not practical because the methods to do so were quite expensive and the devices limited to major medical centers or universities.

The methods used to measure energy expenditure are called direct or indirect calorimetry.
The direct method involves measuring the heat released from the body. Indirect calorimetry refers to methods that measure energy expenditure by measuring ventilation and the exchange of oxygen and carbon dioxide by the body. For a variety of technical reasons, the method of indirect calorimetry is the most widely employed.
The most accurate way of assessing REE by indirect calorimetry is the whole room calorimeter. This technique places a person in a closed room that allows energy expenditure to be calculated based on measurements of air samples (indirect calorimetry) obtained from the room. Gas analyzers attached to the unit measure oxygen consumed and carbon dioxide produced. The balance of oxygen consumed and carbon dioxide produced varies according to activity and the utilization of different fuels by the body (carbohydrate, protein and fat). If an individual is moving about the room, and eating, the TEE is measured. If the person is resting, the REE can be measured. By altering the food provided and ingested, this technique can also be used to evaluate the ability of that individual to burn different fuels and measure the differences in the TEF.

Other methods that are quite accurate use a ventilated canopy hood and a so-called metabolic cart. This method also measures a subject’s oxygen consumption and carbon dioxide production to arrive at the resting energy requirement. Although a less complex system than a whole room calorimeter, the equipment is costly and the technique quite labor intensive.

There are now portable devices available that can measure resting metabolic rate fairly accurately. These handheld indirect calorimeters measure oxygen consumption and determine RMR and are being used in many weight management clinics and other health and fitness facilities. Devices include the MedGem made by HealtheTech and ReeVue made by Korr.

An alternative to direct measurement is the use of a predictive equation to determine RMR. Several have been developed with the Harris and Benedict equation one of the most popular. This equation derives from work done in 1919 and many experts in the field have suggested use of the equation should be abandoned in favor of others that have been developed using more modern techniques and subjects more representative of today’s overweight population.

My preference is the Mifflin-St Jeor Equation developed from a study of participants in the RENO Diet-Heart Study done in the early 1990s. As you can tell, it takes into account differences in sex, weight, height, and age to derive the estimate of RMR.
The equation was developed using weight in kilograms (kg), height in centimeters (cm) and age in years (y).

REE (males) = 10 x weight (kg) + 6.25 x height (cm) – 5 x age(y) + 5
REE (females) = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) –161

The kilogram (kg) and centimeter (cm) measurement requirements make the formula somewhat difficult for us metric-challenged Americans so tables have been developed to make it easier for readers to find their RMR. (search on Mifflin-St Jeor Equation and you’ll find some calculators)

For those who prefer to do their own calculation, the following equation can be used:

REE (males) = 4.5 x weight (pounds) + 16 x height (inches) – 5 x age(y) + 5
REE (females) = 4.5 x weight (pounds) + 16 x height (inches) – 5 x age (y) –161
So, for example, if you are a 50 year old woman, 5’6” in height or 66 inches and 300 pounds, your estimated REE is:

REE = 4.5 times 300 pounds + 16 times 66 inches – 161
REE = 1350 +1056 - 161
REE = 2245
Now correct for age
REE = 2245 – 5 times age in years
REE = 2245 – 5 times 50 or 250
REE = 1995

REMEMBER:

Weight maitenance = REE x 1.3


Therefore, this 50 year old woman, living an average sedentary lifestyle, would need:

Calories to maintain her 300 pounds = REE x 1.3
= 1995 x 1.3 or 2594 calories

It should be obvious to you from looking at the equation and that chart that REE is closely linked to your weight. It increases with weight gain and decreases with weight loss. There is nobody who weighs 250 pounds who can’t lose weight on less than 1000 calories although I have had patients tell me this is their experience.

Another alternative to direct measurement and predictive equations is a very simple tool we will call “your factor”. The factor is the number that when multiplied by your weight equals the number of calories needed to maintain your weight.

Current weight x (the factor) = number of calories needed to maintain your weight

This equation assumes a sedentary lifestyle as well. You will notice that it does not correct for height or age and, therefore, is not going to be as accurate. In general, a man will require 10-12 times his weight to maintain his weight while living sedentary lifestyle. A woman will require about 9-11 times her weight to maintain her weight. More obese and older individuals have a factor in the lower end of the range. The number will tend to go up a little as you lose weight and do down if you gain weight.

In other words, a 125 pound woman will need about 125 x 11 or 1375 calories a day to maintain her weight. A 300-pound woman will need 9 times her weight 2700 calories a day to maintain her weight. This does not mean the 300-pound woman has a slower metabolism and that is what contributed to the obesity in the first place. Rather, the 300-pound woman has a higher proportion of body fat than the 125-pound woman does. Fat is essentially storage tissue and not very active tissue (doesn’t burn a lot of calories). Lean tissue like muscle is active and burns a lot a calories. The more obese person needs fewer calories per pound because more of the “pounds” are fat.

You will notice that the factor method is a good approximation of the TEE. For example, our 5’6” 300 pound 50 year old female had an estimated TEE using the REE equation of 2594 caloires. Using the factor method and a factor of 9, we arrived at 2700 calories.

In the absence of direct measurements, these calculations are good enough and can get you started on your weight loss program. You can fine tone your Calorie Equation as you monitior you weight loss at a particular calorie intake. If you have doubts, underestimate your estimated TEE by the REE equation or factor method by 10 percent.
For example, rather than “believing” your TEE is 2600 calories each day, recalculate it at 2600 – 10% or 2340 and work with that number. Don’t, however, believe, you TEE is 1200 calories when the calculations tell you it is 2600. It just isn’t so. That kind of “belief” is wrong and will simply perpetuate you weight problem. You have to understand the facts about your metabolism and be realistic. Stop fooling yourself!!

Now we are ready to construct your Calorie Equation. This will become the foundation for you weight management program.

To lose a pound of fat, we have to create a calorie deficit of 3,500 calories since a pound of fat contains 3,500 calories. Now someone reading the posting – that physics buff again - is going to say that isn’t true since a pound is 454 grams and there are 9 calories/gram of fat. Therefore, a pound of fat should contain 4086 calories. Well, that is true. However, fat is 10% water and water has no calories so subtract about 10% from 4086. Also, there is the issue of the TEF or cost of metabolizing fat. A few calories are burning in the process of absorption and digestion within the body. So the 3500 calories per pound of fat is very close.

We will call this the 3500 calories = 1 pound rule. Now let’s use the rule to make a few simple calculations.

How to calculate your weight loss on a particular calorie intake:
If you are a 40 year old woman, 5’6” in height and weigh 200 pounds, you are consuming about 200 x 10 or 2000 calories a day by the factor method or 2074 calories by the REE equation method. Let’s use the 2000 calorie estimate to keep it simple.

There are 3,500 calories in a pound of fat as we just learned. If you want to lose a pound, you need to eat 3,500 calories less than you need. For this woman, eating 1500 calories a day is 500 calories less than she needs to maintain her 200 pounds. If she does this for 7 days (500 calories x 7 = 3500 calories), she would lose a pound.

What if you eat 100 calories more a day for a year? 100 calories x 365 days in a year = 36,500 calories. 36,500 calories divided by 3,500 calories in a pound = about 10 and ½ pounds. In other words, just eating an extra 100 calories a day can cause you to gain 10-11 pounds over a year. On a more positive note, cutting back just 100 calories a day can help you lose 10-11 pounds in a year.

We will call this the 100 calories = 10 to a 11 pounds in a year rule. Think how this rule can help you map out a long-term goal. Say you want to be 30 pounds lighter in a year. You would need to knock off about 300 calories from current lifestyle. You could do this with 200 calories less food and 100 calories more exercise or some other combination of your choosing.

Now you can construct your Calorie Equation. Again, using the example of the 200 pound woman with an estimated current TEE of 2000 calories and assuming no extra activity:


Estimated current TEE 2000 calories
Weight loss goal 1 lb per week
Calorie deficit required 3500 calories (since 1 lb = 3500 calories)
Calorie deficit per day -500
Calorie Equation 2000 – 500 or 1500 caloires/day to realize
Desired weight loss goal


The simple truth is that only calories count. In order to be successful with your weight, you now realize you must have a fundamental understanding about how your metabolism works and how may calories you need to maintain your weight. As I mentioned previously, I often tell patients with weight problems that the requirements for self-management are similar, in principle, to the requirements of for self-management that patients who have with diabetes must learn.

Well, people with weight problems need to understand how their metabolism works and address the calorie requirements of their bodies. The Calorie Equation is the start of the process. Now, you will need to learn calorie values of foods so that you know how many calories you are consuming. As other postings will emphasize, this is not an easy task. It requires some study as you as learn calorie values and practice as you implement that new knowledge on a daily basis. For patients with diabetes, it requires many hours of initial instruction and a lifetime of ongoing monitoring and study to be competent self-managers. I’m not sure I can put a number on the hours you might need to become a competent “weight manager” but I am sure that you can do it if you avoid the hype and concentrate on the facts and practical suggestions contained in these postings.

Earlier in this posting, I alluded to a few things that can speed up your metabolism. There is a lot of hype surrounding some of these products. Don’t buy it.

We have hormones in our systems called catecholamines – epinephrine and norepinephrine. Lay people often refer to these hormones as “ adrenalin”. They are also called our “fight-fright” hormones since increased amounts of them caused the increased heart rate, sweating and that “prepared” feeling that occurs should when we get ready to fight or run from a scary situation. Naturally, such hormones effect metabolism and are associated with the need to divert calories to heat or energy production, a process often referred to as thermogenesis. Many of the products that as associated with claims that they speed up the metabolism are linked to the catecholamine system in our bodies.

Caffeine, contained in our beloved coffee, is a substance that is associated with an increase in the metabolic rate or enhanced thermogenesis. It is also found in tea, colas and chocolate. Caffeine belongs to a group of chemicals called xanthines that include theophylline, a drug some of you may be familiar with since it is used in the treatment of lung diseases like emphysema and asthma. In fact, its official chemical name is trimethylxanthine. Caffeine inhibits different enzymes that are capable of effecting how long the catecholamines are active in your system. In so doing, xanthines like caffeine, stimulate the nervous system and can cause people to feel more alert, less drowsy which is, of course, why we use coffee as our morning “wake-me-up”. However, too much caffeine can be bad for you resulting in restlessness, nervousness, agitation, inability to fall asleep, elevated blood pressure and a rapid heart rate. The effect of caffeine in usual doses on the metabolic rate is quite modest.

Ma Huang, also called ephedra, is a Chinese herb that has been used medicinally in China for more than four millenniums. In 1887, ephedrine was isolated from it, and it was nearly a half-century later before the full medicinal value of ephedrine was realized in the treatment of asthma and other allergic conditions. There is an American species of this herb, but it contains only trace amounts of ephedrine. It nevertheless played a part in folk medicine and was popular among Indians and early settlers who both attested to its health-giving properties. The most common use of the American species was to make a tea given various names including Mormon tea, squaw tea, and cowboy tea. These teas were considered good decongestants, tonics, diuretics, and fever and cold remedies.

Ephedrine is a stimulant and closely related to the naturally occurring catecholamines in our bodies. For that reason, it is associated with a higher rate of metabolism. It has been widely promoted as a substance that can aid weight loss, enhance sports performance, and increase energy. Many products actually promote a combination of ephedra and caffeine.

Unfortunately, ephedra can also be dangerous and could kill you if used inappropriately. Numerous injuries and deaths associated with ephedra have been reported to the Food and Drug Administration (FDA). The FDA has been issuing warning related to ephedra for years. Because ephedra is a central nervous system stimulant, it can cause symptoms of sleeplessness, anxiety, and nervousness if taken in too large quantities. It can act as a heart or cardiac stimulant and be associated with elevations in blood pressure and cardiac arrhythmias (irregular heartbeats). People with heart conditions, high blood pressure, thyroid disease, and diabetes should definitely avoid Ma Huang or ephedra.

In February 2003, the FDA sent more than two dozen warning letters to firms marketing dietary supplements that contain ephedrine alkaloids. They warned them not to make misleading or false claims and proposed a warning label for all ephedra-containing products to highlight the potential for serious and even life-threatening side effects. Despite the FDA’s interest, the market for ephedra remained huge.

All that ended in 2004. On December 30, 2003, Health and Human Services Secretary Tommy Thompson announced a ban on the sale of ephedra. The FDA published a final rule on April 12, 2004, that bans the sale of dietary supplements containing ephedrine alkaloids

Naturally, a legal fight ensued. Some companies stood to lose millions in sales. The legal battle went all the way to the Supreme Court. Recently, the U.S Supreme Court ruled it would not consider an appeal brought by one of the distributor for ephedra-containing products to try an overturn the FDA ruling. Has this stopped the sale of ephedra-containing products? Of course not! Do a simple search on ephedra on the Internet and you will still find plenty of sites promoting and willing to sell you the stuff.

Bitter orange is another substances advertised as a “thermogenic”agent and “metabolic enhancer”. The FDA is taking a close look because it contains synephrine, a stimulant chemically related to ephedra. It is also called citrus aurantium and is found in foods such as orange marmalade. Synephrine is not as potent as ephedra but some extracts are sold that contain fairly high doses and could be harmful. Naturally, the hucksters try to get an edge on one another by combining bitter synephrine with caffeine or green tea extracts that can potentiate the risk.

Green tea and green tea extracts are also taunted as stimulants of the metabolic rate. Green tea contains caffeine but also contains ingredients called catechin polyphenols. These catechins block one of the enzymes (catechol O-methyltransferase) that break down norepinephrine. It sticks around longer, therefore, increasing the amount of calories burned by the body. Naturally, there are people out there who are promoting bottled green tea extract as they the “only clinically proven, ephedra-free diet product that can increase thermogenesis and shift the body's substrate utilization in favor of fat oxidation”.
For $40 dollars a month or more, you can pop these capsules and watch the fat just burn away. Do you really think that will work?

Everyone has heard of CortiSlim, advertised way too much on the radio. The simplistic message is “Stress makes us fat. Stress makes you release cortisol and cortisol stimulates your hunger and makes you fat”. Really?! Look carefully at the label and you will notice CortiSlim contains green tea extract and bitter orange peel extract. Taking these stimulants should relax you and reduce cortisol levels? Again, there are some half-truths in the advertising. Cortisol levels are normal in the blood and urine in people who are obese. However, people who are obese have higher production rates of this hormone. Because they metabolize the extra cortisol that is made at a slightly higher rate as well, the blood levels stay normal. Weight loss lowers these production rates. You don’t need CortiSlim. Prices vary but I noticed one promoter for CortiSlim selling it on the Internet for $50 per bottle containing 60 tablets. The “advanced dose” is 6 tablets per day. Let’s see - $50 every 10 days or over $1800 a year. You probably do need $1800 to use for something worthwhile. And you might be able to get some of the money back now that the Federal Trade Commission has alleged that CortiSlim was advertised with false and unsubstantiated weight loss claims. They also suggested that CortiStress was advertised with false and unsubstantiated disease prevention claims.

Nicotine also has a thermogenic effect. In fact, a pack-a-day habit of cigarettes can enhance thermogenesis to the tune of 4-5%. In other works, 100-200 calories per day depending on the dose of nicotine derived from the chosen brand. No one should pursue nicotine-containing products as a means of weight loss but it does help explain why many smokers are thinner and some of the weight gain that occurs after someone quits smoking.

Although the effects of fidgeting might belong, more appropriately, in the exercise posting, we don’t often think of fidgeting as exercise or activity. It is perceived more as a habit or characteristic of a particular individual. Nevertheless, it can have a significant effect on the number of calories required to maintain your weight each day. In fact, a study in the American Journal of Clinical Nutrition in December 2000 demonstrated that some individuals could fidget away up to 800 calories a day! There are, of course, people who can’t seem to sit still. Hands and feet are tapping or swinging even when sitting in a quiet room with no one around. Some people can’t stand still – like to pace, shifting their weight constantly foot-to-foot. Those are all calorie-burning activities and, if done over and over again, do add up. Great, now we will have the new breakthrough Fidgeting Diet, with detailed instructions on how to fidget for greatest impact. That book will probably sell well!

Or how about the chewing gum diet? Have you ever noticed how much effort a cow puts into chewing? It has been estimated that a cow chewing away as they do can increase their calorie expenditure by about 20%. What happens when a human being does a little extra chewing? Somebody searching for something to do investigated this issue by carefully measuring the calorie expenditure associated with chewing calorie-free gum at a controlled frequency in a metabolic laboratory in Minnesota. The frequency of chewing was selected after observation of several random gum-chewers walking around the institution. It was found that chewing gum can increase the energy expenditure by about 7-17 calories per hour. Now, let’s see – 10 calories an hour, 10 hours of gum chewing per day (sugar-free, of course) - that would translate into a 10 to 11 pound weight loss over 1 year and some very sore jaw muscles. Maybe this is the secret to how people in Minnesota stay warm in the winter – pop some gum every time you go out side and chew fast.

So by now you should be getting the idea about all the things that can influence your metabolism. We haven’t mentioned the effects of acute illness and injury on your metabolism. Losing weight under such circumstances is usually not your primary concern.



Influences on your metabolism

Age
Weight
Sex
Body composition
Distribution of body fat
Hormones
Illness
Weight gain and loss
Injury
Use of various stimulants i.e. caffeine
Fidgeting
Physical activity

It is probably important for me to mention how various hormones influence your metabolism. As an Endocrinologist, I have been referred hundreds of obese patients over the years that are asking me to examine the possibility of a hormonal abnormality as the primary reason for their obesity. Often, the specific concern has been “It has got to be my thyroid!”

Actually, hormonal causes of obesity are quite rare and generally easy to screen for with a physical examination and a few laboratory tests. Some of the more common hormonal causes of obesity are noted in the Table.

Hormonal causes of obesity

Hypothyroidism
Hypercortisolism
Cushing syndrome
Growth hormone deficiency


It gets more complicated when you start discussing some of the hormonal conditions associated with obesity. In other words, these are conditions where the patient is often obese. There is a measurable different in hormone levels but we are not certain whether the hormone alterations are due to the obesity and underlying condition or whether the hormone alterations may have contributed to the expression of the obesity or underlying condition.

Conditions where hormone alterations and obesity are commonly associated

Type 2 Diabetes Mellitus
Metabolic Syndrome
Polycystic Ovarian Syndrome


The metabolic syndrome is a relatively new term to describe a condition that has become extremely common in America as we have grown fatter. The identification of this syndrome is important since it is linked to a significant increased risk of heart disease – up to 30%. There are various organizations that have slightly different criteria for diagnosing the condition. The most commonly used criteria was developed by the National Cholesterol Education Program (NCEP) Expert Panel and is shown in the table below.



The Metabolic Syndrome
Defined by the presence of three or more of these components:

Central obesity as measured by waist circumference: Men - Greater than 40 inches Women - Greater than 35 inches
Fasting blood triglycerides greater than or equal to 150 mg/dl
Blood HDL cholesterol: Men - Less than 40 mg/dl Women - Less than 50 mg/dl
Blood pressure greater than or equal to 130/85 mmHg
Fasting glucose greater than or equal to 110 mg/dl

As you think about this definition, remember you only have to have three criteria. So if you have slightly elevated blood pressure, a slightly elevated triglycerides, and your waist circumference is a little bit larger than it ought to be, you have the metabolic syndrome. You also have an increased risk of developing and dying from heart disease.

The central obesity, the size of your waist, is though to be the main issue with the metabolic syndrome. Fat or adipose tissue in the abdomen (also called visceral fat) is a different kind of fat tissue than that found stored outside the abdomen or in the legs. Visceral fat is not just a passive storage depot where we put fat to use for energy at a latter date. Visceral fat is active tissue that secretes hormones and inflammatory substances called cytokines or adipokines that can lead to a damage of blood vessels, to high blood pressure, to hardening of the arteries and heart attacks. The amount of visceral fat is also closely linked to resistance to the hormone insulin.

I really should restate what I just wrote. It is, in fact, a revolutionary concept that adipose tissue is not only a reservoir for energy storage but an active secretory organ. The substances released in the bloodstream by fat tissue are surprising numerous. Almost all of them are bad for you in some manner or another. As mentioned, the amount of these substances secreted into the bloodstream is influenced by the amount of fat tissue you have and where you store it.

This has given rise to the concept of “lipotoxicity”. The idea that excess amount of fat tissue can be toxic to you. This is akin to the concept of glucotoxicity that we often talk about in diabetes. High sugars or glucose in the bloodstream are toxic to the eyes, kidney, and nerve tissue and can lead to retinal disease, blindness, kidney failure, and nerve damage with numbness in the feet. Likewise, excess fat stored within the abdomen and within the organs can be toxic to the body, contributing to insulin resistance and the development of blood vessel disease leading to heart attacks and strokes. In fact, many obese individuals have excess fat stored in the liver and that excess fat can be toxic to the liver leading to inflammation and even cirrhosis. Yet another example of the toxic effects of excess fat.

Insulin is, of course, the hormone that helps regulate blood sugar levels. Patients with Type 2 diabetes have a genetic disorder that makes them insulin resistance. They require more insulin to do the same work done in a non-diabetic individual. Obesity is closely linked with the development of Type 2 diabetes and that obesity is usually “trunkal” – obvious in the belly, in men, often called the “beer gut”. If examined, much of this extra belly weight is visceral fat, inside the abdomen, around the organs, and within the organs.
Type 2 diabetes is also associated with high blood pressure, abnormal triglycerides and HDL-cholesterol, and much increased risk for heart disease.

The amount of visceral fat and the extent of the insulin resistance caused by that excess visceral fat are features Type 2 diabetes and the metabolic syndrome have in common.
The safest, most effective and preferred way to reduce insulin resistance in patients with the metabolic syndrome and Type 2 diabetes is weight loss. The visceral fat is mobilized and lost with weight loss to a greater extent than fat in other areas. A 10% weight loss can have a tremendous effect on the amount of insulin resistance, reducing the blood pressure and improving the blood lipids.

There are also hosts of other hormones understudy that may play a role in obesity. A major focus of this new research is on the role of a variety of gut hormones play in regulating metabolism and appetite. The list is quite long but includes gherlin, CCK, GLP-1, GIP and PYY.

Gherlin appears to be an appetite-stimulating hormone and is produced by the stomach. The secretion of the hormone peaks before a meal and falls after it. In humans, average ghrelin levels correlate with body weight: They are highest in skinny people and lowest in fat ones. If you diet, the amount of the gherlin increases. It appears to work by sending its signal to the feeding center in the brain, within the hypothalamus. Interestingly, the levels of gherlin drop dramatically in obese people who have undergone a stomach-reducing procedure known as gastric-bypass surgery. Maybe this is why such individuals don’t seem to have as much hunger or interest in food after the procedure. Some day, we might be able to control gherlin levels with medication, a new drug, something far less dramatic than gastric surgery.

Glucagon- like peptide 1 (GLP-1) is also under active study. A naturally occuring compound called exenatide that is found in the saliva of the Gila Monster (marketed as Byetta), and has the same properties as naturally occuring GLP-1, is used for the treatment of Type 2 diabetes. GLP-1 is made by intestinal cells and released with food intake. It stimulates insulin release but also acts to reduce the appetite. It sends a signal to the feeding center in the brain and helps produce a sense of fullness or satiety. This gut-brain talk makes some sense. We eat and hormones signal the brain to tell us we are full and should stop eating. It is interesting to note that about 80% of patients with diabetes that are treated with exenatide (Byetta) lose some weight. This drug has been very helpful to many of my obese Type 2 patients, improving their diabetes control but also helping them drop some pounds. Hopefully, studies will be done in the future to test the usefulness of exenatide in obese individuals without diabetes.

As mentioned, there are a variety of peptides produced by fat tissue that are under study including leptin and adiponectin. Leptin deficient animals are obese and it was hoped that leptin deficiency and its correction would be part of the obesity story in humans. In fact, leptin levels are high in obese individuals and leptin administration to obese subjects has been fairly disappointing as weight loss treatment. Adiponectin is one of the few good hormones to be produced by fat cells. Unfortunately, the level of adiponectin good down as one gains weight. Adiponectin helps to reduce insulin resistance and inflammation in the blood vessels. Further understanding as to the role of these hormones or mediators may open up new treatment opportunities in the future.

Having told you about these hormones, it is still calorie balance and the calorie equation that determines your weight. Yes, hypothyroidism, if untreated, may slow your metabolism and make you gain weight if you continue to consume the same number of calories as when you were well. If you ate less, matching the new requirement of a slower metabolism, you would not gain weight despite the untreated hypothyroid condition. I have seen many patients over the years that have been diagnosed with significant hypothyroidism and had not experienced major weight gain. Some, no weight gain at all.
I have seen far more people who insisted that their thyroid function must be way off and the reason for their obesity when, in fact, their thyroid status was perfectly normal.

Metabolism

Tip and Tools

1. TEE = REE + TEF + Activity
2. REE x 1.3 = total daily energy expenditure for the average sedentary individual
3. Use the Mifflin-St.Jeor equation to calculate your total daily energy expenditure.
4. REE can be directly measured as well but takes special equipment
5. Another way of estimating daily energy requirements is the “factor” method. Use your weight times a factor of 9-11 if you are female and 10-12 if you are male. Use the lower factor if you are over 300 pounds or over 50 years of age.
6. 3500 calories = 1 pound of fat (the 3500 calorie rule)
7. Plus or minus 100 calories a day is plus or minus 11 pounds in a year (the 100 calorie rule)
8. Only calories count.
9. The hormonal causes of altered metabolism are uncommon and easily screened for with simple laboratory tests
10. There are various stimulants available to increase the metabolic rate. They are not recommended and in the case of ephedra, dangerous.
11. The Metabolic Syndrome is quite common and imparts a 30% increased risk for heart disease. See if you are susceptible by measuring your waist size.
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