A Fat Regulator In The Body
By Beatrice Trum Hunter
Consumers' Research Magazine 7/99
Leptin, a hormone made by the body's fat cells, is thought to play a role in regulating body fat by acting as an appetite suppressor. Leptin was discovered only as recently as 1994. Researchers are trying to understand its underlying mechanisms. Apparently, leptin not only regulates fat, but seems to have additional roles as well.
When leptin functions properly, it signals the body to stop eating by producing a feeling of fullness. High leptin levels in obese individuals may reflect malfunctioning of leptin.
People with high leptin levels in the blood are more likely to have insulin resistance than those with lower levels.. Insulin resistance is a condition in which cells do not respond effectively to insulin's message to take up sugar from the bloodstream. People with insulin resistance are at greater risk of developing diabetes, high blood pressure, and low levels of beneficial high-density lipoprotein (HDL) cholesterol. These conditions can contribute to heart disease development.
Cholesterol is a poor predictor of heart disease. Some people with normal - range blood cholesterol nevertheless have heart attacks. Measuring blood leptin levels might be a better marker for the potential risk of heart disease in people who show none of the traditional signs associated with this condition, including high blood cholesterol.
Leptin may play a role in diseases associated with a fat abdomen, a feature common in aging. A person with an "apple" shaped body, with fat deposited mainly around the waist rather than on the thighs or hips, is at greater risk of insulin resistance and heart disease.
In rat studies, leptin enhanced insulin's effects significantly. Moderately obese animals, given an infusion of leptin for eight days, ate less and lost weight. The fat loss from their abdomens was greater than from other body parts.
Leptin may regulate weight in young children. Lactating women have lower concentrations of leptin in their milk than in their blood. The breast may not make or concentrate leptin, but passes leptin to the nursing infant from the mother's blood, indirectly through the milk. This finding suggests that the leptin delivered in breast milk may lead to some mechanism that regulates the child's weight later in life. If this is confirmed, it adds yet another benefit, among many, offered by breast milk but not available from feeding formulas.
In experiments with mice, injected leptin helped obese animals lose weight. Could this have similar effects in overweight humans? Leptin passes safety tests, and was injected into 70 obese adult volunteers in the Program of Obesity and Metabolism at Tufts University. All participants were on individually tailored weight- reduction diets that provided 500 kilocalories less than each person's basic daily energy needs. By the end of the first month, all participants lost weight. The amounts lost were proportionate to their leptin intake levels. Those injected with the highest leptin amounts lost an average of nearly 16 pounds each over 6 months. Some participants lost weight at all dose levels, but the amount lost was highly variable.
Leptin may play a role in adult onset type diabetes and in heart disease. A study of 74 healthy men showed that those with the highest leptin concentration in blood were at high risk of suffering from insulin resistance.
Leptin may play an immunologic role. A group of immune cells, known as helper T cells, have leptin receptors (surface proteins that allow a cell to respond to leptin). Leptin encourages helper T cells to secrete certain chemicals that guide the actions of the immune system. For example, they help ward off viruses, bacteria, and fungi. This finding may explain why malnourished people are so vulnerable to many infectious diseases. Malnourishment leads to extensive metabolic and hormonal changes in the body.
Currently, researchers are investigating leptin to learn whether it can prevent malnourished mice from suffering increased rates of infection. If results are positive, leptin could serve as an immune system booster for low birth weight babies who often experience a wasting syndrome.
By leptin's signaling malnutrition or starvation, the body knows when to shut down energy-expensive functions. For example, women with little body fat, such as marathon runners or ballet dancers, often stop menstruating. The body may have interpreted a leptin lack as a signal to avoid reproduction. Falling leptin concentrations in the blood may instruct the body to suspend temporarily the actions of the immune system.
Leptin has been found to play another role, in helping to maintain a balance between the blood supply and the fat tissue mass. Leptin may stimulate the growth of new blood vessels needed when fat increases in volume. Also leptin may spur the growth of endothelial cells that form blood vessels in the maturing egg and early embryo. Also it may spur wound healing. Leptin may be deployed by some cancer cells to recruit blood vessels. If any tumors are found to make leptin, this finding might serve as a useful tool to control tumor growth.
Commonly used weight-control measures such as diet and exercise, as well as drugs, may produce short-term success but not sustained weight loss. For most people, according to Gerald Bernstein, M.D., president of the American Diabetes Association, "weight loss is an ordeal that requires a truly punitive lifestyle that includes a remarkable reduction in calories." The discovery of leptin as fat regulator, as well as its other roles in the body, contributes fresh insights for long recognized problems.
The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244
By Beatrice Trum Hunter
Consumers' Research Magazine 7/99
Leptin, a hormone made by the body's fat cells, is thought to play a role in regulating body fat by acting as an appetite suppressor. Leptin was discovered only as recently as 1994. Researchers are trying to understand its underlying mechanisms. Apparently, leptin not only regulates fat, but seems to have additional roles as well.
When leptin functions properly, it signals the body to stop eating by producing a feeling of fullness. High leptin levels in obese individuals may reflect malfunctioning of leptin.
People with high leptin levels in the blood are more likely to have insulin resistance than those with lower levels.. Insulin resistance is a condition in which cells do not respond effectively to insulin's message to take up sugar from the bloodstream. People with insulin resistance are at greater risk of developing diabetes, high blood pressure, and low levels of beneficial high-density lipoprotein (HDL) cholesterol. These conditions can contribute to heart disease development.
Cholesterol is a poor predictor of heart disease. Some people with normal - range blood cholesterol nevertheless have heart attacks. Measuring blood leptin levels might be a better marker for the potential risk of heart disease in people who show none of the traditional signs associated with this condition, including high blood cholesterol.
Leptin may play a role in diseases associated with a fat abdomen, a feature common in aging. A person with an "apple" shaped body, with fat deposited mainly around the waist rather than on the thighs or hips, is at greater risk of insulin resistance and heart disease.
In rat studies, leptin enhanced insulin's effects significantly. Moderately obese animals, given an infusion of leptin for eight days, ate less and lost weight. The fat loss from their abdomens was greater than from other body parts.
Leptin may regulate weight in young children. Lactating women have lower concentrations of leptin in their milk than in their blood. The breast may not make or concentrate leptin, but passes leptin to the nursing infant from the mother's blood, indirectly through the milk. This finding suggests that the leptin delivered in breast milk may lead to some mechanism that regulates the child's weight later in life. If this is confirmed, it adds yet another benefit, among many, offered by breast milk but not available from feeding formulas.
In experiments with mice, injected leptin helped obese animals lose weight. Could this have similar effects in overweight humans? Leptin passes safety tests, and was injected into 70 obese adult volunteers in the Program of Obesity and Metabolism at Tufts University. All participants were on individually tailored weight- reduction diets that provided 500 kilocalories less than each person's basic daily energy needs. By the end of the first month, all participants lost weight. The amounts lost were proportionate to their leptin intake levels. Those injected with the highest leptin amounts lost an average of nearly 16 pounds each over 6 months. Some participants lost weight at all dose levels, but the amount lost was highly variable.
Leptin may play a role in adult onset type diabetes and in heart disease. A study of 74 healthy men showed that those with the highest leptin concentration in blood were at high risk of suffering from insulin resistance.
Leptin may play an immunologic role. A group of immune cells, known as helper T cells, have leptin receptors (surface proteins that allow a cell to respond to leptin). Leptin encourages helper T cells to secrete certain chemicals that guide the actions of the immune system. For example, they help ward off viruses, bacteria, and fungi. This finding may explain why malnourished people are so vulnerable to many infectious diseases. Malnourishment leads to extensive metabolic and hormonal changes in the body.
Currently, researchers are investigating leptin to learn whether it can prevent malnourished mice from suffering increased rates of infection. If results are positive, leptin could serve as an immune system booster for low birth weight babies who often experience a wasting syndrome.
By leptin's signaling malnutrition or starvation, the body knows when to shut down energy-expensive functions. For example, women with little body fat, such as marathon runners or ballet dancers, often stop menstruating. The body may have interpreted a leptin lack as a signal to avoid reproduction. Falling leptin concentrations in the blood may instruct the body to suspend temporarily the actions of the immune system.
Leptin has been found to play another role, in helping to maintain a balance between the blood supply and the fat tissue mass. Leptin may stimulate the growth of new blood vessels needed when fat increases in volume. Also leptin may spur the growth of endothelial cells that form blood vessels in the maturing egg and early embryo. Also it may spur wound healing. Leptin may be deployed by some cancer cells to recruit blood vessels. If any tumors are found to make leptin, this finding might serve as a useful tool to control tumor growth.
Commonly used weight-control measures such as diet and exercise, as well as drugs, may produce short-term success but not sustained weight loss. For most people, according to Gerald Bernstein, M.D., president of the American Diabetes Association, "weight loss is an ordeal that requires a truly punitive lifestyle that includes a remarkable reduction in calories." The discovery of leptin as fat regulator, as well as its other roles in the body, contributes fresh insights for long recognized problems.
The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244
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