Body Fat: Hard Facts About Soft Tissue

[getraw]

BODY FAT: HARD FACTS ABOUT SOFT TISSUE

by M. Doug McGuff, MD


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Fat is an amazing tissue. It has ensured survival of our species through two ice ages and never ending drought and famine. A mere pound of fat stores an astounding 3,500 Calories for delayed use at any time in the future. As dormant tissue, there is almost no metabolic cost for keeping it on the body. As a member of the human species we all owe our existence to fat. Even more amazing than fat's capabilities are the number of misconceptions surrounding this specialized body tissue.

Probably the biggest misconception regarding fat is the idea that it is unhealthy. Actually, fat is probably the main reason we are even here in the first place. Throughout human history, the ready availability of food was the exception rather than the rule. Our ability to eat when food was available and to store excess caloric energy for future use allowed us to survive when food was not available. Fat storage is the sign of good health, it signals that metabolic resources are abundant and the organism is healthy. An extreme overabundance of bodyfat places stresses on the body and can be unhealthy. However, the degree of leanness (or lack of bodyfat) that is currently in vogue is probably just as unhealthy for up to 80% of the population. Unhealthy levels of bodyfat have been increasing every decade. It seems that an adaptation that has allowed us to survive through history is now killing us in modern times.

Ask almost anyone why modern man is becoming more obese and you will get a similar answer from just about everyone. Most people believe that the labor-saving technologies of modern life have made us more sedentary, and we are much less physically active than our predecessors. Since physical activity burns calories, and we are less physically active than we once were, we are unable to burn off the calories like we used to. This argument seems logical, but the argument is incorrect for 2 basic reasons. First, physical activity burns much less calories than we have been lead to believe (we will discuss this in detail later in this chapter). Suffice to say that to survive we must be able to use our energy efficiently lest we starve to death in the process of hunting and gathering food. Secondly, our ancestors were not as physically active as we think they were. The work of anthropologists who observe primitive peoples in various regions of the globe show that a primitive hunter/gatherer lifestyle is much less physically active than that of modern man. In Australia, aborigines alternate between the modern world and traditional aboriginal life. While in their more primitive mode, these aborigines are noted to be much less active. So, despite popular opinions to the contrary, it does not appear that increased activity is the solution to modern obesity.

The real problem with modern obesity is food abundance. If I were to give you a jumbo industrial role of toilet paper and allowed you to hold it while I unraveled it, we wound end up with a very long strand of toilet paper. If I tore of the last square of toilet paper and gave you the entire rest of the strand, we could use your long strand of toilet paper to represent the length of human history where starvation was a real day to day threat. The single square in my hand would represent the length of human history where starvation was not much of a threat. Not since the end of the Great Depression and World War II has starvation not been a real possibility. We have about 150,000 generations where efficient fat storage was essential for survival, and 3-4 generations where efficient fat storage can lead to obesity. The problem is not that we are inactive, the problem is that calories are so readily available to be consumed. An hour of jogging will burn only about 150 calories above your basal metabolic rate, but it only takes about 30 seconds to eat 150 calories of cookies. We judge the value of our meals on the size of the portions we are given. When we go out to eat, we want to leave full. Studies show that there are about 1,000 Calories between being satisfied and feeling full. Even more frightening is that there are between 2,000 and 3,000 calories between feeling full and feeling stuffed. If you go out to an all-you-can-eat food bar and leave feeling stuffed, you may have consumed as many as 4,000 unneeded calories. When this happens we typically go out for a jog the next day to "burn off those calories". But to burn off that many calories would require you to jog continously for 27 hours. The problem is not that we don't burn enough calories, it's that we put too many calories down our neck.


Leptin: the genetics of fat storage
As anyone with a bodyfat problem knows, there seems to be a strong setpoint for how much body fat a particular individual has. This setpoint is controlled by a gene called the ob gene that produces a protein called Leptin. Leptin is a strong suppressor of appetitie and food intake. As your bodyfat rises, more leptin is produced and your appetite declines so that your bodyfat stabilizes. If your body fat falls, your leptin production declines and your appetite is disinhibited. It seems that we inherit a bodyfat setpoint that is most effecient for our environment and the environment of our ancestors.

Why exercise doesn't burn many calories
Go to the health club and climb on a stair stepper or treadmill. Program the machine by plugging in your weight, select your speed or program and begin your workout. As you plod along on the apparatus you are driven along by the ever-increasing number on the screen that indicates the number of calories that you have burned. Eventually you go long enough to burn 300 calories and you are left with a feeling of accomplishment. Now, as you wipe the sweat from your brow and catch your breath, let me ask you a question. Why did the machine ask you to program in your weight? If you answered to calculate how many calories you burn you are right. What you most likely failed to consider is the main reason it needs your weight is to calculate your basal metabolic rate. The average male will maintain his weight on about 3200 calories a day. That is about 140 calories an hour at rest. So the 300 calories burned are not calories burned above your basal metabolic rate, they are calories burned including your basal metabolic rate. So for your time on the treadmill, you burned about 160 calories above your baseline. If you eat just 3 cookies, you have completely undone about an hour's worth of work. Think about it...if we were so metabolically inefficient as to burn 300 calories at the rate the exercise equipment says you do, would we ever have survived as a species. The calories burned hunting and gathering would have caused us to die of starvation before we could ever have found anything to eat. At that rate of calorie burn, we would barely have enough metabolic economy to survive a trip to the grocery store. Most people have accepted blindly the information displayed on exercise equipment and as such have turned exercise into a form of guilt absolution. Have dessert (600 calories of pie) and feel guilty? Just go to the health club and work on the stepper until 600 calories tick by on the screen. Other than the fact that this simply seems pathetic, it also just doesn't work.


Let us assume that you have the determination and time to do such a workout 7 days a week. If we take the 300 calories burned and subtract out your basal metabolic rate of 140 calories, we are left with 160 calories burned. There are 3,500 calories in a pound of fat. If your appetite is not spurned by the exercise (as it commonly is) and you keep a stable calorie intake, it would take you 21.875 days to burn off a pound of fat with the extra activity. This is assuming that no other variables are present. Unfortunately there is a big variable that almost no-one accounts for...muscle loss. In order to exercise long enough to reach the 300 calorie mark on the stepper or treadmill, you have to perform low intensity steady state activity. Steady state activity does not place much demand on the muscles, that is why it can be carried out for so long. Rather than demanding use of a large percentage of your muscle fibers, you are actually using a small percentage of your weakest, slow-twitch fibers over and over. When you perform this type of exercise your body can adapt by actually losing muscle. Since you use such a small percentage of your muscle mass to do the work, additional muscle is perceived as dead weight, useless and burdensome. If a person persisted in 7 day a week steady state training they could easily lose about 5 pounds of muscle tissue. Muscle tissue is the most metabolically expensive tissue we have; it takes between 50 and 100 calories a day just to keep a pound of muscle alive.

[tatman3177]

very good info to have.. thanks

[FreeBirdbulker]

I remember you burn something like 125-140 calories for each mile, doesnt matter if you walk it, jog it, run it, or sprint it. 1 mile=that many calories burned. for cycling, i cant remember i wanna say its 5-7 miles= same amount burned