Chapter 3

Metabolism and Body Composition:

Muscle Against Fat

By Elena Voropay

You Basal Metabolic Rate largely depends on the body composition, or how much fat and lean tissue you carry around. For starters, Body Composition is the technical term used to describe what the body is made of referring to the relative percentages of fat and nonfat tissues (or lean body mass). When all tissues are taken together they make up your body weight. The so-called 'lean' tissues, such as muscle, bone, and organs are metabolically active, while adipose, or fat tissue, is not. You want your metabolism to be as efficient as it can be, so sizzling fat is advised.

Muscle Tissue:

Hard-To-Find. Hard-To-Get. Easy to Use. Easy to Waste.

You probably have heard that muscle is the secret weapon in the war against fat. It’s natural, it grows without drugs or expensive supplements, it improves the look of your body, it gives you strength and more energy to do anything you want. The amount of muscle you have is one of the prime biomarkers of aging, so you may want to keep the lean tissues on - it literally makes you younger. And what's the one thing almost guaranteed to get attention and makes others green with envy? Toned, lean, shapely arms, legs, chest, back, shoulders and a washboard-looking stomach.

As if you ever needed an excuse or another reason to build muscles, this sounds like a great motivator to get you and the rest of the world to work out. That is all good, but there are many other things about muscles that scientists like to hide from the public. Being a champion in the muscle world, I believe you should know the truly fascinating facts of the fruits of iron-busting hours.

You have probably heard that muscles are your reliable security guards which protect your vulnerable body from the invasions of fat. Many people may tell you that muscles burn thousands of calories every day - the more muscle mass you have, the more calories you burn, even when you’re just sitting around. However, contrary to popular belief, your muscles are not the greatest calorie burners. Indeed, muscle is the largest tissue in the entire body composing up to 50-75% of all proteins in the human body, but muscle's estimated metabolic rate is much less than metabolic rate of your brain. In fact, your muscles burn only 20% of all energy, which is not that much at all.

Scientific estimation of the metabolic rate of muscle is only about 10 to 15 kcal/kg per day, which is approximately 4.5 to 7.0 kcal/lb per day.

So, if you add five kilograms of lean mass, not an easy job to do as you may already know, you will burn only 75 more calories in 24 hours. Bummer! And you thought that you can eat all you want after an hour of working out.

I don't know how you will react to what I just told you, but when I first found out about the miserable amount of calories each kilo of my light flesh nukes each day I was ravenous, to say the least. I have spent an entire year in the weight room area drowning in an ocean of sweat building my so-hard-to-keep 5 kilograms of muscles in order to burn the miserable 75 calories between tonight's dinner and tomorrow night's caloric galore! What a waste! If increasing your metabolic rate is the only reason for your gym routine, you could just pass a cookie to your girlfriend instead of eating it yourself and remain in energy balance. This way, you won't have to worry about having to burn the sweet calories. Should you skip the workout and a cookie or go for both? I hope the decision is an easy one to make. Admit it – building muscles is hard, but it is a worthwhile experience.

Adding lean mass has long term benefits that other aerobic training or best supplements in the world can’t match. Muscle is considered “active tissue” because it requires energy to sustain itself by means other than caloric energy. First, even though 75 calories may not seem like a lot, these will add up to roughly 27,000 additional calories in a year! Considering that a kilogram of fat has 7,000 calories (9 calories per gram of fat), you can really nuke quite a bit of hideous lazy adipose.

For example, by gaining 5 kg of muscle, without any additional dieting or excessive training, you will naturally melt away around 4 kilograms of fat in a year. If you manage to keep just these kilos of lean mass, a mere 5000 grams for another ten years, you may be able to lose 40 kilograms of fat, at least theoretically. With passionate persistence necessary to achieve the muscle-building goals, you will secure yourself from many age-related and obesity-related jiggers.

Another reason for muscle's high-octane power is their effect on various metabolic hormones, such as Testosterone, Growth Hormone, Insulin-like Growth Factor-1, Insulin, Leptin, Thyroxin, Cortisol and other metabolic boosters to name a few. The more muscle tissue you have, the higher the levels of your energy-burning hormones will be. So, it is not just the lean tissue itself that consumes energy, but its effect on other systems in the body which can shift your metabolic engine into a high gear. Building new muscle is actually nature’s way of keeping you healthy.

As you would expect, there is a lot more stuff hiding in the muscles and the way they work is something you can't miss. You will have an opportunity to discover the miracle of motion in the chapters “Flexing Muscles”, “Muscle Fiber: From Chicken Run to Porky Bum”, “How Muscles Grow”, “Pain In The Bum: The Mystery of Muscle Soreness Uncovered”, and many others.

Get Fat and Burn Calories!

While lean tissues are the logs that keep the caloric fire raging, your fat is like a piece of paper and a match. It doesn't add much at all to your BMR. For fat being such a dormant mattress, there is almost no metabolic cost for keeping it on the body. Almost, but not entirely. Fat, or adipose tissue, burns 5% of all calories. It's not huge, but it adds up. Someone carrying 50-100 lbs of fat is burning 150-300 calories per day to sustain that fat. So, don't disregard your fat and think that there there is no good reason to have it.

How can fat burn calories and be so important in your overall metabolic rate, you say? Well, not all fat is fat. In other words, if you look at your fat cell under the microscope, only 60% to 85% of the weight of white adipose tissue is fat or lipid, with 90-99% being triglycerides.

And guess what – your fat cells can have anywhere from 5% to 30 % water and 3 % protein! The rest is made up of small amounts of free fatty acids, triglycerides, cholesterol, phospho-lipid and minute quantities of cholesterol ester and mono glyceride. In this lipid mixture, 6 Fatty Acids make up approximately 90% of the total, and these are Myristic, Plamitic, Palmitoleic, Stearic, Oleic, and Linoleic. Each of these acids may be used for either hormone production, energy supply and/or have an effect on how and when you use the calories supplied and stored in your body. They all are important, but some of these may be better for your efficient metabolism.

It is this much for fat burn.

What about energy-giving effect of fat?

Typically, a human body carries about 50,000 to 60,000 calories of energy worth of fat cells throughout the body. Obese adults typically have a lot more – because their fat cells are bigger and there are more adipose cells in their systems as well – around 60 to 100 billion fat cells, compared with 30 to 50 billion for non-obese adults.

A mere pound of fat stores an astounding 3,500 calories, and a kilo of white stagnant tissue is 7,000 calories which you carry around with you as an energy reserve in case, forbid heavens, there is no food to eat. Assuming you could burn 100 % fat as fuel, which in reality is impossible, this is enough energy for a 150 pound/75 kg person to walk roughly 35 miles or so before using it all up. That's ONE pound or 454 grams of fat only.

Now there is a little discrepancy in how much energy is stored in a kilo or pound of body fat.

It is commonly said that a gram of fat contains 9 calories. But there are 1,000 grams in a kilo and 454 grams in a pound. So, theoretically 1,000 grams of fat should contain 9,000 calories (1,000 x 9), not the proclaimed 7,000 and a pound of body fat must have 4,086 calories (9 x 454), not 3,500. The reason for the is that body fat, or adipose tissue, contains not only fat, but also other substances including protein, connective tissue, and water. The dietary fat referred to in the nutritional analysis of food is pure, which is where the 9 calories come from. Looking at it another way, a gram of body fat contains only 7.7 calories versus the 9 calories found in pure fat. Because of the differences in the two types of fat, it is appropriate to use the 7,000 per kilo and 3,500 calories per pound figure when discussing fat "burned" by activity, and the 9 calories per gram figure when discussing the nutritional content of food. So, if you want to melt the 50 grams of consumed fat from the last weekend all-you-can-eat-pizza binge you will need to run, walk, cycle more than if your goal is to shed the 50 grams worth of cellulite.

As a stored source of energy, dietary fat has an advantage over carbohydrate - the energy density is higher while the relative weight is lower. Fats are a rich source of potential energy ATP generation and can fuel your system for days of famine. Dietary fat provides the highest concentration of energy of all the nutrients, twice the calorie density of proteins or carbohydrates – 9 calories vs. 4 and 4 respectively. Plus, fatty acids provide more adenosine triphosphate (ATP) per molecule than glucose.

Color Up Your Cover Up:

Brown Fat – Metabolic Furnace

Now you are about to be revealed something truly astonishing – your body captures healthy fat as well. Just like not all dietary fats are bad, not all body fats are bad either. It is known as brown adipose tissue. Brown fat is a poorly understood tissue that seems to act the opposite of white fat, the ordinary stuff of bulging waistlines. This type of tissue is actually very healthy and you want to carry as much of it as possible. Even though brown fat is still fat, it has the unique ability to generate heat and burn energy rather than conserving it.

The reason these fat cells are brown is because they are supplied with lots of blood and contain small lipid droplets tucked between tiny energy factories called mitochondria, the chemical structure which makes energy. Most of mitochondria in your body is found in muscle fibers involved in aerobic activities. Mitochondria is the silver bullet of all your caloric burn needs, and brown fat has plenty of it.

Instead of serving as a storage bank of energy, the lipid in brown adipose tissue releases energy directly as heat. It is used in heat production when your body gets cold. When you step into an overly ventilated gym, you naturally activate your brown fat to keep your system nice and warm. And there is another great time when the brown fat knows it's alive – when you eat too much! The excess caloric intake elevates your body temperature bringing up the diet-induced-thermogenesis.

Brown fat cells get the signal and start pumping their engines helping you burn all the excess calories faster. The mechanism of heat generation is related to the metabolism of the mitochondria. Mitochondria from brown adipose tissue have a specific carrier called uncoupling protein that transfers protons from outside to inside without subsequent production of ATP. In other words, your metabolism goes up without any physical activity. The pathway, according to the new report, is controlled by a gene and protein known as PRDM16 that is found in brown but not in white fat - the type that stores excess calories and causes waistlines to bulge.

You can find this type of brown adipose body tissue mainly around the neck and large blood vessels of the throat. In mice, brown fat cells are found throughout the body and are present during the entire life cycle. In humans, they are principally found in new-borns, helping their tiny bodies generate heat. Brown fat cells largely disappear by adulthood, but their precursors still remain in the body, lodged in white-fat depots. Don't you wish it was the white fat that disappeared with aging?

The more brown fat you have, the more heat you generate, and the more calories you burn. This tissue makes you feel warm and is important in controlling body temperature. If you have little brown fat, you've got a “freezer” type metabolism, are cold even in warm conditions, have lower thyroid gland production and your metabolism is quite slow. You also don’t burn foods well, and a lot of what you eat turns to ordinary white fat.

On the other hand, if you are blessed with a lot of brown fat, you have a “furnace” type metabolism. You burn body fuels so fast, that it seems like everything you eat just evaporates – no fat deposits! All the calories explode just like coals on a fire. The more you consume, the more you burn. How much brown fat do you have? This is a difficult question to answer because it is difficult to measure. When the fat is measured, you get the total number of all fat cells, but there is no way to separate the colors or the functions of each fat, brown and white. What is known is that white fat can mostly be found underneath your skin, but it also surrounds internal organs.

Genetics seems to play a role in how the body handles brown fat. Brown fat is activated by Thyroid hormone and appears to respond to vitamin C, Zinc, and Copper supplementation. While you can't change your genetics yet, there is hope to find a way to alter human adult white fat cells into brown fat cells as a cure for obesity. Early researchers believe that the PRDM16 gene from which protein is manufactured at higher levels may be the key into unlocking the metabolic mystery. Experiments using mice fat cells are being conducted now.

You will find a great deal of information about fat, where and how it is stored, what exactly is cellulite and why do women are fatter than men, how and why we become fat and how to lose dangerous ugly layer of blubber forever in the chapters “Where Is The Fat Hiding?” and “Turning Fat Into Muscle” and many others.

Body Size:

Get Big To Get Small

There was a theory that fat people have a slower metabolism and burn less food. I am sure you may know a fat person, or have heard of one who says that no matter how little he or she eats, the calories just don't get used. Fat people usually blame genetics and say that no diet has ever helped them – metabolism works against their best intentions. The theory originated from some early studies when overweight individuals recorded their own food intake over a period of time and showed that they eat the same amount of calories as thin people and couldn't explain why these calories were not burned. The greatest revelation arrived when the undercover behavior was brought to light – the victims of so-thought slow metabolism consistently under-reported their entire supply, according to more recent investigations.

What happened to metabolism of those on plumpy side? Aside from various abnormal conditions, increased appetite, lack of physical activity, high stress levels and hormonal imbalances, most fat cells were created from simple caloric surplus. Slow metabolic rate may sound like a good excuse some fat food-lovers and exercise-haters use. Conversely, thin people pride their discipline, extremes of dieting and physical activity for having a trim body shape, but this is not always the case. In fact, it is just the opposite – big people have a much higher metabolism than small people.

Big bodies of constant dieters are actually more efficient and waste less energy, therefore storing more for emergencies of starvation. This metabolic effect is inherited from our ancestors where shortage of food was very common. Our hunter-gatherers didn't have a clue whether their hunt for meat would be successful and if there would be enough nourishment to feed a group. Thankfully, today you don't have to hunt for your prime-rib all-you-can-eat dinner. At least in the civilized world, most of us are lucky enough to go to bed and wake up in the morning without fear of not having anything to eat. If your fridge becomes half empty, you get paranoid and go shopping, even though you have enough food in your kitchen to feed a family of 10 for at least a few months. But the body doesn't know this and it kind of likes to do its own thing. If you over-feed yourself at any one time, the reserves will find their storage places – in the liver, muscles and in fat. Then, if you cut your calories dramatically, the metabolic rate drops by up to 20% in fear of famine.

Does this mean that the metabolism became less efficient when the overflow of cookies and cheesecakes had no limits? Absolutely not. Fat people have certainly changed their metabolic rate – they increased it and in fact burn more calories at rest than slim people. Recent discoveries in measurement of metabolic rate have clearly demonstrated that fat people use more energy and burn more food calories than average people do. This is because they not only have to carry a lot more weight when they move, but they also have a lot more muscle tissue and larger internal organs, the utmost metabolic burners. At complete rest, larger people need more energy to pump the blood around the body and to keep moving.

Plus, fat people must eat more food just to sustain their body size. Eating itself is a catabolic activity and demands a lot of energy for digestion and complete breakdown of nutrients. What is even more interesting is that fat folks would actually gain less weight or lose weight faster than thin people on the same diet. Bigger people also lose more calories simply from having a larger surface area. More energy is needed to maintain their body temperature because heat loss occurs through skin. The more skin you have – the more heat is lost. So, keeping the body temperature and constantly adjusting it to the environmental changes requires some extra give pushing resting metabolism way up.

What is truly remarkable about body size is that the loss of body heat through larger skin surface area can be so tremendous, that the Resting Metabolic Rate is often reported in kilocalories or kilocalories per square meter of body surface area per hour. Tall people are an excellent example of expedited energy burn from their skin. Then there are some extremely active people who are healthy and fat, and feel a lot less energetic if they start losing weight. I have to mention that there is no set weight which is optimal for everyone. However, there are recommended limits to how much fat is essential, and the rest of the weight is totally an individual issue. The bottom line - the larger or taller you are, even regardless of your body composition - the higher your metabolic rate. Just as a big car uses more fuel, so a bigger person uses more energy.

Inside Addition

So, if muscles burn only 20% of all calories at rest, fat adds up another 5%, where do the 75% of energy are blasted? In the rest of the body. Most people don't know that the heart, lungs, kidneys, brain and liver burn around 75% - 80% of all calories, even though together these represent less than 6% of body mass. Now we are talking energy burn - these tissues have a metabolic rate that is 15 - 40 times greater than their equivalent weight of muscle and 50 - 100 times greater than fat tissue.

There are thousands of cellular reactions are proceeding within your body. Your brain is using glucose for fuel, your lungs ensure you get enough oxygen, your kidneys are filtering the fluids, your liver eye muscles are using energy as you read, your heart is beating, your digestive organs are metabolizing the foods you've eaten before, protein in your muscles is being broken down and re-synthesized, as are fatty acids in your fat cells. Your cells are constantly cycling Sodium into the cell and Potassium out (called the Na/K+ pump) using up energy in the process. All these reactions go on and on without taking a break.

Relative Contribution of Organs and Tissues To Body Weight and BMR:

Adapted from M.Elia, 1992. Organ and tissue contribution to metabolic rate. In Energy metabolism – Tissue determinants and cellular corollaries, edited by J.M.Kinney and H.N.Tucker (New York, NY: Raven Press), 61 – 77.

How Lean (or Fat) Are You, Really?

Have you been working out and dieting religiously during the cold winter months? Or were you a loyal member of “all-you-can-eat-pizza and drink-beer-while-watching TV” club? Well, your body will show the results of your leisure time spending by either added fat or added muscle. If you skipped the 'pizza and beer' part, but still preferred to stay in front of the tube instead of hitting the weights or the elliptical, you may have ignored some potential damage in the form of beer belly, and maybe even lost weight.

It's great, right? Not really - there is a great chance you have lost a lot of lean mass through detraining. The calories were burned, but if most of them came from muscle breakdown, then dieting was a completely worthless torture. Frustrated? Don't worry.

Body fat is something that most people cringe at. The truth is, body fat is essential for many reasons, however, carrying too much fat tissue is not all so good. For one, it doesn't look as appealing as rock-hard muscles, nor does cellulite and love handles overhanging your belt project a healthy state. So what is healthy? In order to figure out healthy body fat measurements, we have to understand the basics of our anatomy.

We carry two kinds of fat in our bodies. The first one is called essential fat which is stored in small amounts in bone marrow, organs, the Central Nervous System and muscles. You need it for the normal, healthy functioning of all these body systems. Essential fat should be around 3% - 5% for men and 8% -12% for women. The reason for such big difference is because women carry fat in the breasts, pelvis, hips and thighs believed necessary for normal female reproductive function. The rest of the percentage is storage fat which is stocked for energy.

If you have pumped your fair deal of iron for a while, chances are you are overweight. I don't say you are fat, just overweight. And that's great because I assume that most of that weight comes from metabolically active muscles, strong thick bones, and a big heart full of love for gym sweat. An average bodybuilder, for example, may be 8% body fat, yet at a 150kg is "over-weight" by a typical height-weight chart. Therefore, these charts are a worthless creation of doctors and dietitians paranoid of degenerative diseases of a food-driven nation. Each individual has his or her own ideal body weight for optimal health and athletic performance and some people are just naturally leaner than others. Then you can differentiate into body types, add all sorts of requirements for specific sporting obsessions, throw in the competition season cycling, and you have an encyclopedia of weight requirements. As you get older, your healthy body fat percentage increases.

So, to stay focused, all you need to know at any one time is if you are getting closer to your ideal body composition. When looking at healthy body fat percentages, age, along with gender, you may get a rough estimate of where you want to be. The key to maintaining a healthy body fat percentage is not having too much storage fat, but enough essential fat. Methods for figuring this out have been known and used for decades.

I remember when I first computed my body fat and my lean mass. Then I started putting on kilos of mass. Of course, I was training really hard and eating extra-large food portions, so my initial thought was that the weight I was gaining had to be mostly muscle mass. But my gains in strength were not proportional – the poundage was increasing on the scale only, not on the weight stacks I was lifting at the gym. I was frustrated, and like many people at this point, made up the excuse, "My genetics must be keeping me from it". The reality was that my initial body fat measurement was off by a long shot, as were the subsequent calculations.

Sure, body composition is a valid measure to use because you do want your body fat to go down and the lean mass to go up. Being able to state that you lost exactly 5.5 kilos of fat and gained 4.5 kilos of lean mass in a given time frame might be great for supplement ads or to promote the latest weight loss fad, but numbers that precise aren't realistic without expensive, laboratory-grade equipment, or at least the hands-on testing of a very skilled professional. It is hard to predict how much lean mass you will gain or lose. I have seen so many people, who do not even realise what lean mass is (such as muscle vs. stored body water) and get frustrated by loss of lean mass due to poor body fat calculations. Lean mass is not only muscle -- it includes most of the non-fat substances in your body. Bones, blood, lymph, tendons, ligaments, even fat itself contains water (around 25%), so when you lose a significant amount of fat, you also lose a significant amount of water. This will register as a loss of lean mass, but that does not mean you lost muscle!

The reality is that there are too many things which are involved in your current body composition – how well hydrated you are, whether you've eaten or not in the past few hours, your diet composition and what types of supplements you use, how long it's been since you trained; for women, the issue is even more complex due to their hormonal fluctuations throughout the day and the monthly period. Luckily for us, there are many ways to check your body fat and lean mass. If you are curious and want to track your progress, use a combination of measurements.

But before you proceed, I advise to use body fat, along with the tape measure and your scale weight, to track trends. Don't worry about trying to figure out what you will weigh at a particular level of body fat, because every person is different. Really, who cares except you? If you are healthy, feel great and comfortable in your own skin, does that exact number really matter? Unless you are aiming to participate in a bodybuilding competition, there really is no reason to get yourself to shreds if you feel worse than a dried prune. And please, don't use your reflection in the mirror or how well your pants fit as a way to check your progress. Your pants may shrink in the washing/drying cycle, and you may never see your abs defined because the genetics simply don't allow for this to happen – no matter how little body fat you pack. It is amusing sometimes to see people who are far from seeing their six-pack claim they are 8% body fat while some who are ripped to shreds swear they are 15% body fat or more. This is an example where the number becomes too much of the focus.