Energy is probably something, but physicists have never been able to figure out exactly what that is. What are we paying them for? They can describe the various forms of energy - heat, light, mechanical power etc. They can measure it different ways. For example the energy in food or gasoline is in chemical bonds and can be measured in calories. Some physicists define energy, lamely, as the ability to do work. Work is force acting through a distance. Energy could be potential or stored work, or it could be kinetic and getting done. So energy sounds like work and should be avoided. Energy comes in indivisible packets called quanta. You can never have half of a quantum. This little known fact is why I don't even start many jobs around the house. The study of energy is called thermodynamics. Scientists have found that God made two laws of thermodynamics that have never been broken. The first law of thermodynamics is the law of conservation of energy. This law states that energy cannot be created or destroyed, only changed around. God made all the energy in the universe in the beginning and it will all be there in the end. Einstein figured out that matter and energy are equivalent in some sense, but even he didn't know what energy was. God's second law of thermodynamics is more complicated. It says that entropy always increases. Entropy is wasted energy and it always has to happen. Entropy is the energy you lose to heat when you burn gasoline and make you car go. This inevitable cost of entropy is like paying taxes. It makes perpetual motion machines impossible. Entropy happens in our bodies too. Lots of energy must be wasted whenever we do anything useful. When we think or move around, we also make heat, which is definitely a hassle in the summer. Another name of entropy is disorder. The universe is constantly and rapidly getting more and more disordered. Whenever you straighten out the top of your desk, you make the rest of the universe more messed up and the desk strives mightily to get messed up again. In the end, the universe will be maximally disorganized and cold and useless.
The first law of thermodynamics says that energy can neither be created nor destroyed. That means that the energy you take in as food must always be exactly equal to the energy you burn or store. This is why smug doctors and so-called friends say that you wouldn't be fat if you didn't eat so much and exercise so little. These worse-than-enemies often quote the rule that one pound equals 3500 Calories. But fat people say that they don't eat any more than you do, or they always eat less. They also claim that they get plenty of exercise. Are they lying? Are they claiming to be in violation of the first law of thermodynamics? Let's look at rats. They can't lie. There are several species of mouse and rat that are genetically fat. These species have names like Zucker and ob/ob and Fatty. These critters get fat and stay fat on Purina rat chow rations that would starve regular rats. These rats teach obesity researchers two important things - 1. Within a range of Calorie intakes, rat weight and fat storage does not depend on how much they eat. And 2. Obesity runs in rat families. But rats aren't people Studies in humans show the same thing. Obese persons gain or maintain excess weight on the same Calories that maintain people of normal weight. Also when anyone loses weight, he must eat fewer Calories to maintain the reduction. This is true whether he started out fat or skinny. Another way to state this is that one pound may equal about 3500 Calories when you weigh about what you usually weigh; if you lose weight then it takes fewer Calories to gain back the weight. This phenomenon is progressive until your weight becomes stable again no matter how little you eat. There is a limit to how little a person can eat and not progress to starve to death. But it is very little.
As hard as it may be to lose weight, it turns out to be even harder to gain it. This is what I kept telling my grandmother. She used to make me eat lots of linguine #19 and drink eggnog because she thought I was too thin. A famous study was done in the early 1970's on worthy volunteers in the Vermont State Prison. These prisoners were asked by Sims and coworkers to get fat. These researchers wanted to study experimental obesity. They asked the state prisoners, men who had a lot of time on their hands, to eat supplemented Swanson TV dinners to the tune of up to 9000 Calories a day. All the prisoners gained some, but not much. In frustration Sims asked them to stop all strenuous activities and watch TV, together with the big eating job. That didn't work either. It turned out to be quite an onerous task for them to eat so much. The Sims study was designed to examine the metabolic effects of experimental obesity. But he failed in the first step. He could not really create "experimental obesity." Instead, these reports are quoted as demonstrating how hard it is to increase weight. A more recent study examining this phenomenon was reported from the Rockefeller University where a lot of research on obesity goes on. Leibel, Rosenbaum and Hirsch took eighteen obese subjects and 23 subjects who had never been obese and increased and decreased their weight by about 10%. This degree of weight change seems to be reasonably do-able. They found that maintenance of a reduced or elevated body weight is associated with compensatory changes in energy expenditure. They commented that the metabolic compensation for weight change helps to explain the poor long-term effectiveness of treatments for obesity. This is not really new information. When the subjects of these studies who had to increase their weights were allowed to stop the forced eating, their excess weight just fell off in a matter of days to weeks. This is just the kind of fantasy weight loss that is sold on supermarket checkout counters and bought by somebody - not me or you.
Most adults stay about the same weight for long periods of time. The body seems to be programmed to protect a set weight and shape. Since we can't violate the first law of thermodynamics, we must conclude that we eat exactly the same amount that we burn up, all the time. Or if we eat more one day, then we eat less another, such that in the long run, energy intake and output are exactly equal. A third possibility is that the body can vary the efficiency with which it burns or stores Calories as demonstrated in the studies mentioned above. This third option is a much simpler way to explain the facts even before we spend lots of time and money on studies. Somehow we compensate metabolically for the variability of our behavior. Also our appetite is controlled by mechanisms beyond our awareness.
Before the turn of the century, German investigators did careful measurements on themselves and dogs. They noted that when they ate more than usual, the increased Calories could be accounted for in the weight they gained, but only for a few pounds. Then their weight stabilized even though they kept eating more. They couldn't find where the extra Calories were going. They weren't in the stools, they weren't in the urine, and they stopped gaining weight, so it wasn?t in their fat stores. They figured that the body must turn on a metabolism that ran only when it ate too much. They called this metabolism Luxuskonsumption. Luxuskonsumption gives it a German name but doesn't explain anything. Scientists divide energy expenditure in the body into several compartments. First is the cost of assimilating the food you eat, called diet induced thermogenesis (DIT) or specific dynamic action (SDA) or the thermic effect of feeding. This depends on how much you eat and exactly what you eat. It is the cost of absorbing and handling the food. It usually represents about 10% of the Calories you ingest. Next there's basal metabolism.
Basal metabolic rate (BMR) is the energy requirement of doing nothing. It is the metabolism that must be maintained at all times to stay alive. It is the rate at which Calories are burned when you are at complete rest in a comfortable environment several hours after any food intake; something like what you're usually doing at 3 a.m. in the morning if you are not having a nightmare about obesity. Basal metabolism is necessary to maintain the integrity and readiness of all your body processes and to keep your brain doing whatever it does. For most people who don't run marathons or race in the Tour de France, this is where most of your food goes. Basal metabolism is increased by wounds, burns, surgery, pregnancy, fever and other stress. It is decreased by dieting, starvation, malnutrition, and increased age. Ounce for ounce, the kidneys are the hungriest organs. The brain and the liver in an adult each use one fifth of the BMR. The kidneys, heart, brain and liver together account for two-thirds of basal metabolism and these organs don't change their appetites much under normal conditions. In an infant the brain is the biggest eater. Relative metabolic shares in newborns and in adults. With permission from Vaclav Smil, Energies 1999 by MIT Press Basal metabolism correlates with your size, or more exactly, with the size of your lean body mass. Lean body mass is the fat free part. Age and sex and surface area also factor into determining your basal metabolism. There is also some familial tendency. Your basal metabolism is like your parents' or brother's. After all these things and others are considered there is still some individual variation. For reference we can use the example of an average 150 lb, 40 year old husband. His basal metabolism plus the little energy he needs to eat and process food plus a minimum amount of physical activity for a desk job, equals about 2000 Calories per day. Most of these husbands always eat more than 2000 Calories per day. Obese people as a group have the same average basal metabolism as thin people. Actually obese people have an increased basal metabolism because they have more lean body mass together with the extra fat and they have more surface area. When we correct for the extra lean body mass and surface area, then obese people fall back into the middle of the bell shaped curve of basal metabolism, at least as near as the most sensitive instruments can detect. The final two places that the energy you eat can go are exercise or "nonresting energy expenditure" and stored fat. Those are two chapters of their own. So let?s go back to those Vermont State prisoners and the Rockefeller University subjects and the Germans and their dogs. In which metabolic compartments can we put this Luxuscontraption? A further question that comes to mind is - Do we waste Calories when we eat too much and hunker down when we're starved with the same metabolic machinery? The answer is, "yes." All the compartments - thermic effects of eating, basal metabolism, and nonresting energy expenditure, contribute and they all work together in each direction. All of these conspire against us when we presume to change God's will. We can further complicate the picture if we're masochistic. Lots of complicated things happen when we eat. Sugars, proteins and fats are metabolized differently. If we infuse glucose, or simple sugar, directly into the blood stream and then watch what happens, we find that after storage, transformation and immediate energy needs are accounted for, there is still a percentage of this glucose that is disposed of, or wasted, and this wasting increases as we increase the rate of glucose infusion. Furthermore it is noted that noradrenaline levels increase in the blood as the glucose infusion increases. This would indicate that the nervous system is somehow sensing and reacting to the glucose. This extra-consumption can be blocked by drugs that block noradrenaline action, evidence that the sites of Luxuskonsumption are directly or indirectly under nervous control. Some surmise that brown fat is the site of some of the Luxuskonsumption. It is present in humans; it has lots of nerves connected to it, and at least in animals that hibernate, it is used for heat production when the animal is otherwise doing nothing - hibernating. The medical term for heat production is thermogenesis. There is evidence that curvaceous people and rats have impaired thermogenesis when they eat or when it's cold or when we give them doses of norepinephrine or just anytime. Lean people turn on the extra thermogenesis or Luxuskonsumption, when they eat well. Another term for Luxuskonsumtion is adaptive thermogenesis. Trying to prove that this Luxukonsumption is related to thermogenesis, is harder than you might think. We are talking about tiny amounts of energy. Besides thermogenesis, there are lots of other energy-expensive things that the body does all the time. It would not be hard to waste a little extra here or there and it would be next to impossible to detect it.
A little imbalance - big problems
We've been trying to understand the difference between people of different sizes and there really is no detectable difference if they haven?t been eating too much or dieting to lose weight. But maybe that's the wrong question. The question is, how did they get to be different? But that involves even tinier perturbations. For example, one cracker, say 10 Calories, a day, would be 3650 Calories or more than a pound a year. Leibel, an important obesity researcher, does some arithmetic like this in a recent review (1995). The difference between getting fat or staying thin is teensy-weensy. These differences will be beyond our most sensitive testing even in the laboratory, even on small children, even in rats. Presuming that they are ever so slightly different in the way they dispose of calories, we're still stuck with the question, "Why don't obese people just eat less than everybody else if their bodies are smarter and more efficient or colder?" That is unanswerable so far. The other side of the coin poses the question, why would God make Luxuskonsumption? Does He condone gluttony? Stock and Rothwell have proposed that animals that have special vitamin or mineral requirements need to eat lots of "junk" Calories in order to assure that enough of a scarce nutrient is acquired. Such a situation would require that the animal be able to dispose of the extra Calories in order not to get too fat.
Insulin and Sugar
Insulin is the "fed hormone." It is in charge of getting sugar into all of the cells of the body except the brain cells, which take care of themselves. Fat cells depend on insulin to store glucose that is turned into stored fat but as they become enlarged they get resistant to insulin. When fat cells become resistant, more insulin is necessary and then the fat cells get bigger still and more resistant in a vicious cycle. As this process becomes excessive, the sugar in the blood starts to increase until it spills into the urine. This is diabetes mellitus, (Greek for sweet urine). This is a tremendous waste of Calories. However this should be thought of as a defense against further weight and fat gain when other systems have failed. In other words it is an effect rather than a cause of obesity. It can't explain how obese individuals got that way. A frustration of treating diabetics is that the treatment makes them fatter. For example 33.1% if intensively treated insulin dependant diabetics are obese compared to 19.1% of less intensively treated ones. Also other risk factors, like blood fat and cholesterol levels and blood pressure and coronary artery disease, may be increased by insulin treatment. Insulin stimulates fat cells to take up of free fatty acids from the blood too, not just sugar. Obese persons often have high cholesterol and fat in their blood. It's as if their fat cells are fed up and are trying to dump fat. No real answers to our metaphysical questions here.
I hold patent number 4,822,336 - a blood glucose level sensor. This device is based on the idea that a small bit of yeast implanted where it could be exposed to the glucose in a person's blood would eat some glucose and produce carbon dioxide that in turn could be detected by pressure or pH change or other means. The carbon dioxide level would be a reflection of the glucose level and provide a signal to an insulin pump to guide the administration of insulin to diabetics. Such a device would close the loop and improve treatment for diabetes. A very smart microbiologist, Tim Cassidy, and I tried to develop a practical device based on this principal for over 4 years. We never managed. You see those damned yeasts could make CO2 from the glucose in their environment, sure. But they could also make more yeast cells or store it. Or if they chose, they could make CO2 from glucose they had already stored or eat each other or God knows what. If we couldn't keep tract of the energy in these little buggers how much harder is it going to be to find it in a big creature like you.
Usual energy expenditure = thermogenic effect of food ~ 10% + resting or basal metabolic rate ~ 60% + physical activity ~ 30% ~ total ~ 100% ("~" means almost equal to) If you eat too much or starve yourself all parts of your metabolism adjust to thwart your hubris against God's will. We've found that plump people and trim people are alike in the following ways: -They eat the same -Their basal metabolism is the same -They react the same to weight loss and weight gain. We've found that obese people are different from non-obese people in the following ways: - They are fatter..
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