MIDDLE-AGED janitors rarely make their mark on science. But Caesar Barber
looks like breaking the mould. Last July, Barber, a 56-year-old diabetic and
double heart-attack victim from Brooklyn, sued McDonald's, Burger King, KFC
and Wendy's, claiming that his illnesses were partly their fault. He had
eaten in their restaurants for years, he said, without ever being told that
the food was damaging his health.
Barber's class-action lawsuit was the first volley in a long-awaited legal
assault against the fast-food industry and its role in the obesity epidemic
that is swamping the US health-care system (see "Fat facts"). Inspired by
the success of Big Tobacco, the lawyers behind it believe they can force
fast-food chains to meet their fair share of the enormous cost of caring for
obesity. Pulling the strings is John Banzhaf, of George Washington
University Law School in Washington DC, who masterminded the Big Tobacco
crusade.
That campaign won him plaudits all over the world. But "Big Fat" is a
different matter. To many - including a federal judge who last month
dismissed a similar lawsuit against McDonald's - it seems blatantly absurd.
Surely people who become fat and ill because they have eaten too much fast
food only have themselves to blame?
Perhaps not. New and potentially explosive findings on the biological
effects of fast food suggest that eating yourself into obesity isn't simply
down to a lack of self-control. Some scientists are starting to believe that
bingeing on foods that are excessively high in fat and sugar can cause
changes to your brain and body that make it hard to say no. A few even
believe that the foods can trigger changes that are similar to full-blown
addiction. The research is still at a very early stage, but thanks to Caesar
Barber it is about to be thrust firmly into the limelight.
Taking on the fast-food industry was always going to be a much tougher
assignment than beating the cigarette barons. Tobacco is obviously
addictive. Nobody needs to smoke. And the tobacco companies knew their
products were addictive yet covered it up. None of these accusations can be
levelled at food.
Banzhaf maintains that he can win regardless. He points out that he doesn't
have to prove that the fast-food chains are entirely responsible for
obesity. All he has to do is convince a jury that his clients' health
problems were not entirely their own fault - that the fast-food companies
share the blame. Perhaps, for example, they should have labelled the food to
inform customers of its high calorific value.
Any hint that the food is addictive, though, would make Banzhaf's job a
great deal easier. And he knows it. Banzhaf already says he believes that
fast food has "addictive-like" properties. "We might even discover that it's
possible to become addicted to the all-American meal of burgers and fries,"
he says.
But how can something you need for survival be addictive? The answer could
be in the food itself. The difference between a fast-food meal and a
home-cooked one is the sheer quantity of calories and fat it delivers in one
go. The US Department of Agriculture's recommended daily intake for a normal
adult male is 2800 kilocalories (11,723 kilojoules) and a maximum of 93
grams of fat. A meal at a fast-food outlet - burger, fries, drink and
dessert - can deliver almost all of that in a single sitting (see Diagram).
Biologists are now starting to realise that a binge of these proportions can
trigger physiological changes which mute the hormonal signals that normally
tell you to put down the fork.
In the past decade, researchers have discovered myriad hormones that play a
role in regulating appetite. Under normal conditions these hormones control
eating and help maintain a stable body weight. Leptin, for example, is
continuously secreted by fat cells and its level in the bloodstream
indicates the status of the body's fat reserves. This signal is read by the
hypothalamus, the brain region that coordinates eating behaviour, and taken
as a guideline for keeping reserves stable.
The problem is, people who gain weight develop resistance to leptin's power,
explains Michael Schwartz, an endocrinologist at the University of
Washington in Seattle. "Their brain loses its ability to respond to these
hormones as body fat increases," he says. The fatter they get, and the more
leptin they make, the more insensitive the hypothalamus becomes. Eventually
the hypothalamus interprets the elevated level as normal - and forever after
misreads the drops in leptin caused by weight loss as a starvation warning.
But you don't need to become overweight to perturb your leptin system. The
latest research suggests that it only takes a few fatty meals. In a study
published in December, physiologist Luciano Rossetti of the Albert Einstein
College of Medicine in New York City fed rats a high-fat diet and found that
after just 72 hours the animals had already lost almost all of their ability
to respond to leptin (Diabetes, vol 50, p 2786). The good news, says
Rossetti, is that these changes are reversible. "But the fatter a person
becomes the more resistant they will be to the effects of leptin and the
harder it is to reverse those effects."
Sarah Leibowitz, a neurobiologist at Rockefeller University in New York
City, has more evidence that eating fast food is self-reinforcing. Her
experiments show that exposure to fatty foods may quickly reconfigure the
body's hormonal system to want yet more fat. She has shown that levels of
galanin, a brain peptide that stimulates eating and slows down energy
expenditure, increase in rats when they eat a high-fat diet.
In fact, Leibowitz has found that it only takes one high-fat meal to
stimulate galanin expression in the hypothalamus. When the effects of
galanin are blocked, the animals eat much less fat. "The peptide is itself
responsive to the consumption of fat, which then creates the basis for a
vicious cycle," she says.
What's more, early exposure to fatty food could reconfigure children's
bodies so that they always choose fatty foods. Leibowitz found that when she
fed young rats a high-fat diet, they invariably became obese later in life.
She is still investigating what's going on, but her theory is that an
elevated level of fats called triglycerides in the bloodstream turns on
genes for neuropeptides such as galanin that promote overeating. This
suggests that children fed kids' meals at fast-food restaurants are more
likely to grow up to be burger-scoffing adults.
Rossetti's most recent studies have also found a connection between
triglycerides and food intake. Using a catheter implanted in the brain,
Rossetti delivered lipids directly into the arcuate nucleus - a region of
the hypothalamus - to either normally fed rats or overfed rats, and then
measured their food intake for three days. In the normally fed group the
excess fats curbed food intake by up to 60 per cent. But the overfed rats
just carried on scoffing. What's more, Rossetti discovered that this effect
is not dependent on the composition of the diet, whether high-fat or
high-sugar, but instead depends on the total amount of calories.
Hormonal changes may remove some element of free will, but on its own that
hardly means that fast food is addictive. However, there is another strand
of research that suggests gorging on fat and sugar causes brain changes
normally associated with addictive drugs such as heroin.
It is already well established that food and addiction are closely linked.
Many addiction researchers believe that addictive drugs such as cocaine and
nicotine exert their irresistible pull by hijacking "reward" circuits in the
brain. These circuits evolved to motivate humans to seek healthy rewards
such as food and sex. Eating energy-dense food, for example, triggers the
release of endorphins and enkephalins, the brain's natural opioids, which
stimulate a squirt of dopamine into a structure called the nucleus
accumbens, a tiny cluster of cells in the midbrain. Exactly how this
generates a feeling of reward isn't understood, but it is clear that
addictive substances provide a short cut to it - they all seem to increase
levels of dopamine in the nucleus accumbens. Repeated use of addictive
substances is thought to alter the circuitry in as yet unknown ways.
looks like breaking the mould. Last July, Barber, a 56-year-old diabetic and
double heart-attack victim from Brooklyn, sued McDonald's, Burger King, KFC
and Wendy's, claiming that his illnesses were partly their fault. He had
eaten in their restaurants for years, he said, without ever being told that
the food was damaging his health.
Barber's class-action lawsuit was the first volley in a long-awaited legal
assault against the fast-food industry and its role in the obesity epidemic
that is swamping the US health-care system (see "Fat facts"). Inspired by
the success of Big Tobacco, the lawyers behind it believe they can force
fast-food chains to meet their fair share of the enormous cost of caring for
obesity. Pulling the strings is John Banzhaf, of George Washington
University Law School in Washington DC, who masterminded the Big Tobacco
crusade.
That campaign won him plaudits all over the world. But "Big Fat" is a
different matter. To many - including a federal judge who last month
dismissed a similar lawsuit against McDonald's - it seems blatantly absurd.
Surely people who become fat and ill because they have eaten too much fast
food only have themselves to blame?
Perhaps not. New and potentially explosive findings on the biological
effects of fast food suggest that eating yourself into obesity isn't simply
down to a lack of self-control. Some scientists are starting to believe that
bingeing on foods that are excessively high in fat and sugar can cause
changes to your brain and body that make it hard to say no. A few even
believe that the foods can trigger changes that are similar to full-blown
addiction. The research is still at a very early stage, but thanks to Caesar
Barber it is about to be thrust firmly into the limelight.
Taking on the fast-food industry was always going to be a much tougher
assignment than beating the cigarette barons. Tobacco is obviously
addictive. Nobody needs to smoke. And the tobacco companies knew their
products were addictive yet covered it up. None of these accusations can be
levelled at food.
Banzhaf maintains that he can win regardless. He points out that he doesn't
have to prove that the fast-food chains are entirely responsible for
obesity. All he has to do is convince a jury that his clients' health
problems were not entirely their own fault - that the fast-food companies
share the blame. Perhaps, for example, they should have labelled the food to
inform customers of its high calorific value.
Any hint that the food is addictive, though, would make Banzhaf's job a
great deal easier. And he knows it. Banzhaf already says he believes that
fast food has "addictive-like" properties. "We might even discover that it's
possible to become addicted to the all-American meal of burgers and fries,"
he says.
But how can something you need for survival be addictive? The answer could
be in the food itself. The difference between a fast-food meal and a
home-cooked one is the sheer quantity of calories and fat it delivers in one
go. The US Department of Agriculture's recommended daily intake for a normal
adult male is 2800 kilocalories (11,723 kilojoules) and a maximum of 93
grams of fat. A meal at a fast-food outlet - burger, fries, drink and
dessert - can deliver almost all of that in a single sitting (see Diagram).
Biologists are now starting to realise that a binge of these proportions can
trigger physiological changes which mute the hormonal signals that normally
tell you to put down the fork.
In the past decade, researchers have discovered myriad hormones that play a
role in regulating appetite. Under normal conditions these hormones control
eating and help maintain a stable body weight. Leptin, for example, is
continuously secreted by fat cells and its level in the bloodstream
indicates the status of the body's fat reserves. This signal is read by the
hypothalamus, the brain region that coordinates eating behaviour, and taken
as a guideline for keeping reserves stable.
The problem is, people who gain weight develop resistance to leptin's power,
explains Michael Schwartz, an endocrinologist at the University of
Washington in Seattle. "Their brain loses its ability to respond to these
hormones as body fat increases," he says. The fatter they get, and the more
leptin they make, the more insensitive the hypothalamus becomes. Eventually
the hypothalamus interprets the elevated level as normal - and forever after
misreads the drops in leptin caused by weight loss as a starvation warning.
But you don't need to become overweight to perturb your leptin system. The
latest research suggests that it only takes a few fatty meals. In a study
published in December, physiologist Luciano Rossetti of the Albert Einstein
College of Medicine in New York City fed rats a high-fat diet and found that
after just 72 hours the animals had already lost almost all of their ability
to respond to leptin (Diabetes, vol 50, p 2786). The good news, says
Rossetti, is that these changes are reversible. "But the fatter a person
becomes the more resistant they will be to the effects of leptin and the
harder it is to reverse those effects."
Sarah Leibowitz, a neurobiologist at Rockefeller University in New York
City, has more evidence that eating fast food is self-reinforcing. Her
experiments show that exposure to fatty foods may quickly reconfigure the
body's hormonal system to want yet more fat. She has shown that levels of
galanin, a brain peptide that stimulates eating and slows down energy
expenditure, increase in rats when they eat a high-fat diet.
In fact, Leibowitz has found that it only takes one high-fat meal to
stimulate galanin expression in the hypothalamus. When the effects of
galanin are blocked, the animals eat much less fat. "The peptide is itself
responsive to the consumption of fat, which then creates the basis for a
vicious cycle," she says.
What's more, early exposure to fatty food could reconfigure children's
bodies so that they always choose fatty foods. Leibowitz found that when she
fed young rats a high-fat diet, they invariably became obese later in life.
She is still investigating what's going on, but her theory is that an
elevated level of fats called triglycerides in the bloodstream turns on
genes for neuropeptides such as galanin that promote overeating. This
suggests that children fed kids' meals at fast-food restaurants are more
likely to grow up to be burger-scoffing adults.
Rossetti's most recent studies have also found a connection between
triglycerides and food intake. Using a catheter implanted in the brain,
Rossetti delivered lipids directly into the arcuate nucleus - a region of
the hypothalamus - to either normally fed rats or overfed rats, and then
measured their food intake for three days. In the normally fed group the
excess fats curbed food intake by up to 60 per cent. But the overfed rats
just carried on scoffing. What's more, Rossetti discovered that this effect
is not dependent on the composition of the diet, whether high-fat or
high-sugar, but instead depends on the total amount of calories.
Hormonal changes may remove some element of free will, but on its own that
hardly means that fast food is addictive. However, there is another strand
of research that suggests gorging on fat and sugar causes brain changes
normally associated with addictive drugs such as heroin.
It is already well established that food and addiction are closely linked.
Many addiction researchers believe that addictive drugs such as cocaine and
nicotine exert their irresistible pull by hijacking "reward" circuits in the
brain. These circuits evolved to motivate humans to seek healthy rewards
such as food and sex. Eating energy-dense food, for example, triggers the
release of endorphins and enkephalins, the brain's natural opioids, which
stimulate a squirt of dopamine into a structure called the nucleus
accumbens, a tiny cluster of cells in the midbrain. Exactly how this
generates a feeling of reward isn't understood, but it is clear that
addictive substances provide a short cut to it - they all seem to increase
levels of dopamine in the nucleus accumbens. Repeated use of addictive
substances is thought to alter the circuitry in as yet unknown ways.
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