Sherrie
30-06-2006, 07:55 AM
I thought this was a really interesting article, it is writtem by Barry Groves in response to another article last December:
Why a calorie isn't necessarily a calorie
I liked the story, but it is fatally flawed as it is based on a totally wrong premise: That the cause of obesity is eating too many calories and ont exercising enough.
There have been many studies dating from over 70 years ago to the present day which have demonstrated consistently that the best way to lose weight -- and significantly, to keep it off -- is to eat more fat and cut down on the carbs. I'll leave the reader to look these up -- it will be a useful exercise over the holiday period.
So what went wrong?
Around the end of the nineteenth century, doctors devised a simple concept, based on the First Law of Thermodynamics. They likened the body to a tank, into one end of which energy is poured in the form of food. This, they said, was then either used up or stored. If you used up more than you poured in, you got thinner and if you poured in more than you used, you got fatter. The theory was easy to understand, made sense, obeyed the laws of physics, and for a while it seemed satisfactory. Dieticians could now say, apparently with scientific backing, that fat people must either be eating too much or working too little.
By the start of the 1914‑18 war, however, doubts were creeping in. For instance, diabetes is a defect of carbohydrate metabolism and the treatment for diabetics at that time involved completely depriving them of carbohydrate. In this case, scientists found that the energy input/energy output sums simply did not add up.
By the early 1920s, interest in the theory was renewed. It was found to be impossible to measure the total amount of water in a person at any one time. Therefore, water retention or loss was said to account for any discrepancy in the balance between energy input/output and excess weight. It was decades before this convenient theory was disproved.
In the 1950s, isotope techniques were developed which allowed more accurate measurement of body fat turnover. In addition, it was demonstrated that different foods could alter the amounts of body fat; and that body fat could also be affected by certain responsive glands – the adrenal, thyroid and pituitary glands – even when energy intake was constant.
The flaws exposed
The fact that high‑energy diets are more effective for reducing weight has proved very difficult for dieticians and doctors to accept, because of what looks like a challenge to the laws of thermodynamics. But there are flaws in this theory. To grasp them, we need to go over some basic facts.
The calorie is a unit of heat. The way the energy content of a food is determined is by burning it in a device called a ‘bomb calorimeter’ and measuring the amount of heat it gives off.
One gram of carbohydrate, burnt in this way gives an energy value of 4.2 calories, or more correctly kilocalories (kcals). A gram of protein gives 5.25 kcals. This time, however, one calorie is deducted because a gram of protein does not oxidise readily, it gives rise to urea and other products which must be subtracted. That gives a final figure for protein of 4.25 kcals. Burning a gram of fat in the bomb calorimeter gives 9.2 kcals.
These figures are then rounded to the nearest whole number – 4, 4 and 9 respectively – and are used in calorie charts to indicate the energy values of foodstuffs and, thus, to allow dieters to measure their food intake.
But there are two basic flaws in using these figures to determine the amounts of food we should eat:
1. The more obvious flaw in the argument is that our bodies do not burn foods in the same way that they are burned in a bomb calorimeter. If they did, we would glow in the dark. Our digestive process is quite inefficient. The chemical process whereby blood sugar is oxidised to provide energy produces carbon dioxide. About half is exhaled as carbon dioxide, the other half is excreted in sweat, urine and faeces as energy- containing molecules, the energy values of which must be deducted from the original food intake. All of these vary. For example, eating a lot of fat forms ketones, which can be found in urine. The value of a gram of ketones derived from fat is roughly four calories. So, in this case, nearly half the energy from the fat is lost.
2. The second and more important flaw in the argument is that the body does not use all its food to provide energy. The primary function of dietary proteins, for example, is body cell manufacture and repair: making skin, blood, hair and finger‑ and toe‑nails, etc. The amount of protein needed for this purpose is generally accepted to be about one gram per kilogram of lean body weight. As meats contain approximately 23 grams of protein per 100 grams, a person weighing, say, 70 kg (11 stone) needs to eat about 300 g (11 oz) of meat, or its equivalent, every day just to supply his basic protein needs. Even eating this volume of lean chicken would provide some 465 calories. These calories are not used to supply energy, they contribute nothing to the body’s calorie needs and so must be deducted if you are counting calories.
Much of the fat we eat is also used to provide materials used by the body in processes other than the production of energy: the manufacture of bile acids and hormones, the essential fatty acids for the brain and nervous system, and so on. All these must be deducted as well. Thus trying to determine, from food intake and energy expenditure alone, how much excess energy your body will store as fat will give a completely wrong answer. However, these other factors cannot be measured. Therefore, calorie‑counting, which is the foundation of practically every modern slimming diet, is a complete waste of time.
And there is one more flaw: We are told by the ‘experts’ that ‘a calorie is a calorie’. What they mean is that it is impossible for two diets containing exactly the same number of calories to lead to different weight losses. Yet, over the last century a spate of dietary studies has shown that, calorie for calorie, low-carbohydrate diets are much better at reducing weight than the traditional low-fat diets. ‘Experts’ have heavily criticised these studies saying that the data could not be right because that would violate the laws of thermodynamics. But they don’t. It is important to realise that there is more than one law of thermodynamics. The narrow view that ‘a calorie is a calorie’ might comply with the First Law, but it violates the Second Law of Thermodynamics.
The point is that there is no doubt that low-carb, high-fat diets do have a metabolic advantage when it comes to weight loss, whatever the ‘experts’ say.1 And this metabolic advantage complies fully with the second Law of Thermodynamics – and, incidentally, the First Law as well.
The First Law, as mentioned above, is a conservation law. The Second Law is a dissipation law; it is this Second Law which governs the chemical reactions in our bodies.
Let me use an analogy. The energy in the petrol that fuels your car makes the car go along, but it also produces heat through friction and noise, which we really don’t need. The Second Law is all about efficiency – how much of the energy we put in does useful work and how much is wasted. Thus, although all of the energy in the petrol is accounted for and complies with the First Law, the actual moving of the car, if the waste products (heat and noise) are removed from the equation, does not. The Second Law was developed in this context. And it applies equally when we look at the efficiency of our bodies and how different foods affect our bodies. The Second Law says that no machine is completely efficient: Some of the available energy is lost as heat or in the internal rearrangement of chemical compounds and other changes. And as different foods use different metabolic pathways, with different levels of efficiency, variations in efficiency must be expected. For this reason, the dogma that a ‘calorie is a calorie’ violates the second law of thermodynamics as a matter of principle.
It is the differences in chemical changes within our bodies that make low-carb diets better than low-fat, calorie-controlled ones easier to lose weight on. What the diet dictocrats fail to take into consideration when considering the laws of thermodynamics are the energy losses incurred in the different chemical changes within our bodies. When these are taken into consideration, neither law of thermodynamics is violated.
The correct way to lose weight
So, getting back to the best way to lose weight, the truth is that it’s well nigh impossible to lose weight permanently simply by restricting calories. Eating less and losing excess body fat do not automatically go hand in hand. Certainly enforced starving will make you lose weight – World War II concentration camps proved that. But low-fat, low-calorie, diets (which are essentially the same thing as starving) generate a series of biochemical signals in your body that will take you out of balance, making it more difficult to access stored body fat for energy. In a similar way, diets based on calorie limits invariably fail in the long term – you simply cannot stay on them. People on restrictive diets get tired of feeling hungry and deprived. They go off their diets, put the weight back on – primarily as increased body fat – and then feel bad about themselves for not having enough will power, discipline, or motivation. And feeling bad about things tends to make you want to comfort yourself with yet more carbohydrates in the form of sweets or chocolate, thus adding to the problem.
But you shouldn’t need willpower – no other animal does; all you really need is the right information.
If you change what you eat to a more natural way of eating – a way of eating more like our pre-agricultural ancestors – you won’t have to be overly concerned about how much you eat at all and be continually counting calories. Your body will do that for you, the way it is genetically programmed to do.
The reason so many people are getting fatter now is beacuse they are told to eat the very foods that are the most fattening. Until that is understood and acknowledged, things will continue to get worse.
1. Feinman RD, Fine EJ. Thermodynamics and Metabolic Advantage of Weight Loss Diets. Metabolic Syndrome and Related Disorders 2003; 1: 209- 219.
Competing interests: Author of: Eat, Fat, Get Thin!
http://bmj.bmjjournals.com/cgi/eletters/331/7531/1545#top
Why a calorie isn't necessarily a calorie
I liked the story, but it is fatally flawed as it is based on a totally wrong premise: That the cause of obesity is eating too many calories and ont exercising enough.
There have been many studies dating from over 70 years ago to the present day which have demonstrated consistently that the best way to lose weight -- and significantly, to keep it off -- is to eat more fat and cut down on the carbs. I'll leave the reader to look these up -- it will be a useful exercise over the holiday period.
So what went wrong?
Around the end of the nineteenth century, doctors devised a simple concept, based on the First Law of Thermodynamics. They likened the body to a tank, into one end of which energy is poured in the form of food. This, they said, was then either used up or stored. If you used up more than you poured in, you got thinner and if you poured in more than you used, you got fatter. The theory was easy to understand, made sense, obeyed the laws of physics, and for a while it seemed satisfactory. Dieticians could now say, apparently with scientific backing, that fat people must either be eating too much or working too little.
By the start of the 1914‑18 war, however, doubts were creeping in. For instance, diabetes is a defect of carbohydrate metabolism and the treatment for diabetics at that time involved completely depriving them of carbohydrate. In this case, scientists found that the energy input/energy output sums simply did not add up.
By the early 1920s, interest in the theory was renewed. It was found to be impossible to measure the total amount of water in a person at any one time. Therefore, water retention or loss was said to account for any discrepancy in the balance between energy input/output and excess weight. It was decades before this convenient theory was disproved.
In the 1950s, isotope techniques were developed which allowed more accurate measurement of body fat turnover. In addition, it was demonstrated that different foods could alter the amounts of body fat; and that body fat could also be affected by certain responsive glands – the adrenal, thyroid and pituitary glands – even when energy intake was constant.
The flaws exposed
The fact that high‑energy diets are more effective for reducing weight has proved very difficult for dieticians and doctors to accept, because of what looks like a challenge to the laws of thermodynamics. But there are flaws in this theory. To grasp them, we need to go over some basic facts.
The calorie is a unit of heat. The way the energy content of a food is determined is by burning it in a device called a ‘bomb calorimeter’ and measuring the amount of heat it gives off.
One gram of carbohydrate, burnt in this way gives an energy value of 4.2 calories, or more correctly kilocalories (kcals). A gram of protein gives 5.25 kcals. This time, however, one calorie is deducted because a gram of protein does not oxidise readily, it gives rise to urea and other products which must be subtracted. That gives a final figure for protein of 4.25 kcals. Burning a gram of fat in the bomb calorimeter gives 9.2 kcals.
These figures are then rounded to the nearest whole number – 4, 4 and 9 respectively – and are used in calorie charts to indicate the energy values of foodstuffs and, thus, to allow dieters to measure their food intake.
But there are two basic flaws in using these figures to determine the amounts of food we should eat:
1. The more obvious flaw in the argument is that our bodies do not burn foods in the same way that they are burned in a bomb calorimeter. If they did, we would glow in the dark. Our digestive process is quite inefficient. The chemical process whereby blood sugar is oxidised to provide energy produces carbon dioxide. About half is exhaled as carbon dioxide, the other half is excreted in sweat, urine and faeces as energy- containing molecules, the energy values of which must be deducted from the original food intake. All of these vary. For example, eating a lot of fat forms ketones, which can be found in urine. The value of a gram of ketones derived from fat is roughly four calories. So, in this case, nearly half the energy from the fat is lost.
2. The second and more important flaw in the argument is that the body does not use all its food to provide energy. The primary function of dietary proteins, for example, is body cell manufacture and repair: making skin, blood, hair and finger‑ and toe‑nails, etc. The amount of protein needed for this purpose is generally accepted to be about one gram per kilogram of lean body weight. As meats contain approximately 23 grams of protein per 100 grams, a person weighing, say, 70 kg (11 stone) needs to eat about 300 g (11 oz) of meat, or its equivalent, every day just to supply his basic protein needs. Even eating this volume of lean chicken would provide some 465 calories. These calories are not used to supply energy, they contribute nothing to the body’s calorie needs and so must be deducted if you are counting calories.
Much of the fat we eat is also used to provide materials used by the body in processes other than the production of energy: the manufacture of bile acids and hormones, the essential fatty acids for the brain and nervous system, and so on. All these must be deducted as well. Thus trying to determine, from food intake and energy expenditure alone, how much excess energy your body will store as fat will give a completely wrong answer. However, these other factors cannot be measured. Therefore, calorie‑counting, which is the foundation of practically every modern slimming diet, is a complete waste of time.
And there is one more flaw: We are told by the ‘experts’ that ‘a calorie is a calorie’. What they mean is that it is impossible for two diets containing exactly the same number of calories to lead to different weight losses. Yet, over the last century a spate of dietary studies has shown that, calorie for calorie, low-carbohydrate diets are much better at reducing weight than the traditional low-fat diets. ‘Experts’ have heavily criticised these studies saying that the data could not be right because that would violate the laws of thermodynamics. But they don’t. It is important to realise that there is more than one law of thermodynamics. The narrow view that ‘a calorie is a calorie’ might comply with the First Law, but it violates the Second Law of Thermodynamics.
The point is that there is no doubt that low-carb, high-fat diets do have a metabolic advantage when it comes to weight loss, whatever the ‘experts’ say.1 And this metabolic advantage complies fully with the second Law of Thermodynamics – and, incidentally, the First Law as well.
The First Law, as mentioned above, is a conservation law. The Second Law is a dissipation law; it is this Second Law which governs the chemical reactions in our bodies.
Let me use an analogy. The energy in the petrol that fuels your car makes the car go along, but it also produces heat through friction and noise, which we really don’t need. The Second Law is all about efficiency – how much of the energy we put in does useful work and how much is wasted. Thus, although all of the energy in the petrol is accounted for and complies with the First Law, the actual moving of the car, if the waste products (heat and noise) are removed from the equation, does not. The Second Law was developed in this context. And it applies equally when we look at the efficiency of our bodies and how different foods affect our bodies. The Second Law says that no machine is completely efficient: Some of the available energy is lost as heat or in the internal rearrangement of chemical compounds and other changes. And as different foods use different metabolic pathways, with different levels of efficiency, variations in efficiency must be expected. For this reason, the dogma that a ‘calorie is a calorie’ violates the second law of thermodynamics as a matter of principle.
It is the differences in chemical changes within our bodies that make low-carb diets better than low-fat, calorie-controlled ones easier to lose weight on. What the diet dictocrats fail to take into consideration when considering the laws of thermodynamics are the energy losses incurred in the different chemical changes within our bodies. When these are taken into consideration, neither law of thermodynamics is violated.
The correct way to lose weight
So, getting back to the best way to lose weight, the truth is that it’s well nigh impossible to lose weight permanently simply by restricting calories. Eating less and losing excess body fat do not automatically go hand in hand. Certainly enforced starving will make you lose weight – World War II concentration camps proved that. But low-fat, low-calorie, diets (which are essentially the same thing as starving) generate a series of biochemical signals in your body that will take you out of balance, making it more difficult to access stored body fat for energy. In a similar way, diets based on calorie limits invariably fail in the long term – you simply cannot stay on them. People on restrictive diets get tired of feeling hungry and deprived. They go off their diets, put the weight back on – primarily as increased body fat – and then feel bad about themselves for not having enough will power, discipline, or motivation. And feeling bad about things tends to make you want to comfort yourself with yet more carbohydrates in the form of sweets or chocolate, thus adding to the problem.
But you shouldn’t need willpower – no other animal does; all you really need is the right information.
If you change what you eat to a more natural way of eating – a way of eating more like our pre-agricultural ancestors – you won’t have to be overly concerned about how much you eat at all and be continually counting calories. Your body will do that for you, the way it is genetically programmed to do.
The reason so many people are getting fatter now is beacuse they are told to eat the very foods that are the most fattening. Until that is understood and acknowledged, things will continue to get worse.
1. Feinman RD, Fine EJ. Thermodynamics and Metabolic Advantage of Weight Loss Diets. Metabolic Syndrome and Related Disorders 2003; 1: 209- 219.
Competing interests: Author of: Eat, Fat, Get Thin!
http://bmj.bmjjournals.com/cgi/eletters/331/7531/1545#top