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Why the Body May Waste the Calories From Alcohol - New York Times
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THE so-called Drinking Man's Diet, a treacherous scheme popular in the 1960's that suggested substituting alcohol for sugars and starches to shed unwanted pounds, was based on the puzzling observation that heavy drinkers and alcoholics often lose weight despite intakes of a thousand or more extra alcohol calories each day.
This observation baffled nutritionists, who long believed that every calorie that entered the stomach could eventually turn itself into fat. Alcohol researchers, too, wondered how so many alcohol calories could be wasted by the metabolic system, which millions of Americans knew to be highly efficient at storing extra calories as fat.
Now Dr. Charles S. Lieber, a New York physician who has been plumbing the depths of alcohol's many mysteries since 1957, has come up with a biochemical mechanism that he says largely accounts for the remarkable wastage of alcohol calories in heavy drinkers. Dr. Lieber published his findings in the current issue of The Journal of the American Society for Clinical Nutrition under the title, "Perspectives: Do Alcohol Calories Count?"
The answer, he said, is yes and no: yes, for a moderate social drinker who has a cocktail before dinner or an occasional glass of wine or a beer. For these people, alcohol calories can indeed add up. Body Learns to Waste Calories
But chronic heavy drinking can prime certain metabolic processes and, in effect, train the body to waste the seven calories a gram that alcohol ordinarily provides.
For example, weight gain was negligible in alcoholics who were given 2,000 calories of alcohol daily on top of the 2,500 calories from foods they consumed to maintain their weight. But when the same number of additional calories were fed as chocolate, a steady weight gain resulted.
Thus, the energy waste associated with a heavy intake of alcohol cannot be attributed to a reduction in the intake of other foods. More likely, it results from interference with the body's ability to derive energy from other foods.
According to Dr. Lieber's report, experiments in laboratory animals and in heavy drinkers found that alcohol calories did indeed count for animals and people who consumed a very low-fat diet.
Dr. Lieber, who directs the alcohol research and treatment center at the Bronx Veterans Affairs Medical Center, quickly cautioned that heavy drinkers pay a stiff price for their metabolic inefficiency. The very process that enables their bodies to dissipate alcohol's calories as useless heat also converts a host of environmental and food-borne substances into chemicals that can seriously injure vital organs. Damaging Chemical Byproducts
Some of these chemicals are outright cell poisons; others can initiate cancers, and still others can damage genetic material. Together these effects largely explain why heavy drinking is associated with a number of life-threatening diseases, including cirrhosis of the liver and cancer of the esophagus, said Dr. Lieber, a professor of medicine and pathology at Mount Sinai School of Medicine.
He explained that the body has no way to store alcohol and that very little of it can pass through and be excreted. Thus, nearly all the alcohol a person consumes must be metabolized, a job relegated to the liver. This organ has two main ways to process alcohol, one that generates chemical energy and one that does not.
In moderate drinkers (up to one drink a day for women, two for men), the primary route results in the synthesis of an energy-conserving compound known as ATP, adenosine triphosphate. ATP can then generate useful energy to fuel any number of cellular processes.
But in heavy drinkers, Dr. Lieber and his colleagues showed, the liver disposes of alcohol in a second, energy-wasting way. This mechanism, called the microsomal ethanol oxidizing system, in effect converts alcohol into heat. If the heat is not needed to maintain the person's body temperature, it is wasted.
Hence, few if any of the alcohol calories count when alcohol is processed by the microsomal system.
The hitch is that the microsomes that do the work in this system can do more than process alcohol. These subcellular particles normally convert toxic compounds like drugs and insecticides into less harmful substances that the body can excrete. "But," Dr. Lieber said, "the mechanism can backfire and the microsomes can also oxidize substances into toxic compounds that can cause liver damage." Creating Chemical Havoc
Once the microsomal system is operating full tilt, it can create chemical havoc, generating a host of "active metabolites" that react readily with other chemical compounds or with normal constituents of cells. For example, the microsomal system breaks down alcohol to form a toxic metabolite called acetaldehyde, which binds to proteins like enzymes and to the mitochondria in cells and impairs their ability to function. Mitochondria are organelles within cells that function like powerhouses, generating energy for cellular functions. When they are damaged, liver cells are unable to burn fuel effectively.
The microsomal system can also form liver-damaging substances from various environmental compounds, including industrial solvents, medications (including the over-the-counter pain-killer acetaminophen), anesthetic agents and even some vitamins, like vitamin A, Dr. Lieber said. In addition to acetaldehyde, active metabolites created by the microsomal system include free radicals. These highly reactive substances can activate carcinogens, accelerate cellular aging and directly damage the liver.
"The result is a greater vulnerability to environmental toxins, including alcohol itself," he explained.
The liver normally serves as a sophisticated garbage disposal system, clearing the body of toxic wastes so that they cannot harm healthy tissues. But when the liver is damaged by a chronic assault of large amounts of alcohol, it becomes ineffective as a protective cleanser.
Dr. Lieber said a further problem arises when alcohol is on board because the liver preferentially uses it as fuel in lieu of its usual fuel source, fat. When fat is not burned for fuel, it accumulates in the liver, causing a condition known as fatty liver, the first stage of cirrhosis, a potentially fatal scarring of the liver.
Cirrhosis is a leading cause of death among regular heavy drinkers. In New York City, Dr. Lieber said, cirrhosis is the fourth leading cause of death among people between the ages of 25 and 65. The French, many of whom drink considerable amounts of alcohol daily, have one of the highest rates of liver cirrhosis, even among those who rarely drink enough at any one time to get drunk.
"People who are accustomed to drinking regularly develop both a central nervous system and a metabolic tolerance to alcohol," Dr. Lieber said. "The brain is less affected and the microsomal system gets rid of alcohol more rapidly. But they are not spared alcohol's damaging effects." In other words, those who rely on alcohol for weight control could end up thin but dead.
Why the Body May Waste the Calories From Alcohol - New York Times
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THE so-called Drinking Man's Diet, a treacherous scheme popular in the 1960's that suggested substituting alcohol for sugars and starches to shed unwanted pounds, was based on the puzzling observation that heavy drinkers and alcoholics often lose weight despite intakes of a thousand or more extra alcohol calories each day.
This observation baffled nutritionists, who long believed that every calorie that entered the stomach could eventually turn itself into fat. Alcohol researchers, too, wondered how so many alcohol calories could be wasted by the metabolic system, which millions of Americans knew to be highly efficient at storing extra calories as fat.
Now Dr. Charles S. Lieber, a New York physician who has been plumbing the depths of alcohol's many mysteries since 1957, has come up with a biochemical mechanism that he says largely accounts for the remarkable wastage of alcohol calories in heavy drinkers. Dr. Lieber published his findings in the current issue of The Journal of the American Society for Clinical Nutrition under the title, "Perspectives: Do Alcohol Calories Count?"
The answer, he said, is yes and no: yes, for a moderate social drinker who has a cocktail before dinner or an occasional glass of wine or a beer. For these people, alcohol calories can indeed add up. Body Learns to Waste Calories
But chronic heavy drinking can prime certain metabolic processes and, in effect, train the body to waste the seven calories a gram that alcohol ordinarily provides.
For example, weight gain was negligible in alcoholics who were given 2,000 calories of alcohol daily on top of the 2,500 calories from foods they consumed to maintain their weight. But when the same number of additional calories were fed as chocolate, a steady weight gain resulted.
Thus, the energy waste associated with a heavy intake of alcohol cannot be attributed to a reduction in the intake of other foods. More likely, it results from interference with the body's ability to derive energy from other foods.
According to Dr. Lieber's report, experiments in laboratory animals and in heavy drinkers found that alcohol calories did indeed count for animals and people who consumed a very low-fat diet.
Dr. Lieber, who directs the alcohol research and treatment center at the Bronx Veterans Affairs Medical Center, quickly cautioned that heavy drinkers pay a stiff price for their metabolic inefficiency. The very process that enables their bodies to dissipate alcohol's calories as useless heat also converts a host of environmental and food-borne substances into chemicals that can seriously injure vital organs. Damaging Chemical Byproducts
Some of these chemicals are outright cell poisons; others can initiate cancers, and still others can damage genetic material. Together these effects largely explain why heavy drinking is associated with a number of life-threatening diseases, including cirrhosis of the liver and cancer of the esophagus, said Dr. Lieber, a professor of medicine and pathology at Mount Sinai School of Medicine.
He explained that the body has no way to store alcohol and that very little of it can pass through and be excreted. Thus, nearly all the alcohol a person consumes must be metabolized, a job relegated to the liver. This organ has two main ways to process alcohol, one that generates chemical energy and one that does not.
In moderate drinkers (up to one drink a day for women, two for men), the primary route results in the synthesis of an energy-conserving compound known as ATP, adenosine triphosphate. ATP can then generate useful energy to fuel any number of cellular processes.
But in heavy drinkers, Dr. Lieber and his colleagues showed, the liver disposes of alcohol in a second, energy-wasting way. This mechanism, called the microsomal ethanol oxidizing system, in effect converts alcohol into heat. If the heat is not needed to maintain the person's body temperature, it is wasted.
Hence, few if any of the alcohol calories count when alcohol is processed by the microsomal system.
The hitch is that the microsomes that do the work in this system can do more than process alcohol. These subcellular particles normally convert toxic compounds like drugs and insecticides into less harmful substances that the body can excrete. "But," Dr. Lieber said, "the mechanism can backfire and the microsomes can also oxidize substances into toxic compounds that can cause liver damage." Creating Chemical Havoc
Once the microsomal system is operating full tilt, it can create chemical havoc, generating a host of "active metabolites" that react readily with other chemical compounds or with normal constituents of cells. For example, the microsomal system breaks down alcohol to form a toxic metabolite called acetaldehyde, which binds to proteins like enzymes and to the mitochondria in cells and impairs their ability to function. Mitochondria are organelles within cells that function like powerhouses, generating energy for cellular functions. When they are damaged, liver cells are unable to burn fuel effectively.
The microsomal system can also form liver-damaging substances from various environmental compounds, including industrial solvents, medications (including the over-the-counter pain-killer acetaminophen), anesthetic agents and even some vitamins, like vitamin A, Dr. Lieber said. In addition to acetaldehyde, active metabolites created by the microsomal system include free radicals. These highly reactive substances can activate carcinogens, accelerate cellular aging and directly damage the liver.
"The result is a greater vulnerability to environmental toxins, including alcohol itself," he explained.
The liver normally serves as a sophisticated garbage disposal system, clearing the body of toxic wastes so that they cannot harm healthy tissues. But when the liver is damaged by a chronic assault of large amounts of alcohol, it becomes ineffective as a protective cleanser.
Dr. Lieber said a further problem arises when alcohol is on board because the liver preferentially uses it as fuel in lieu of its usual fuel source, fat. When fat is not burned for fuel, it accumulates in the liver, causing a condition known as fatty liver, the first stage of cirrhosis, a potentially fatal scarring of the liver.
Cirrhosis is a leading cause of death among regular heavy drinkers. In New York City, Dr. Lieber said, cirrhosis is the fourth leading cause of death among people between the ages of 25 and 65. The French, many of whom drink considerable amounts of alcohol daily, have one of the highest rates of liver cirrhosis, even among those who rarely drink enough at any one time to get drunk.
"People who are accustomed to drinking regularly develop both a central nervous system and a metabolic tolerance to alcohol," Dr. Lieber said. "The brain is less affected and the microsomal system gets rid of alcohol more rapidly. But they are not spared alcohol's damaging effects." In other words, those who rely on alcohol for weight control could end up thin but dead.