Childhood obesity: What’s really triggering this epidemic?
"In the United States, 25 percent of all children are obese," reports Dr. Robert H. Lustig, pediatric endocrinologist and director of the Weight Assessment for Teen and Child Health (WATCH) Clinic at UCSF Children's Hospital.
He says childhood obesity is now the biggest public health concern in the world – not just in the United States, but also in every country that adopts a Western diet, including Japan, France and many developing countries.
But what's really triggering this epidemic? And what can be done to solve this problem?
Many people, including the U.S. surgeon general, believe obesity is a matter of personal responsibility – that individuals should take it upon themselves to eat less and exercise more.
But Lustig disagrees. He says, "Obesity is a biochemical abnormality that's been set up by our current food environment."
Children cannot be held accountable
To prove his argument, Lustig explains that in the United States childhood obesity is increasing fastest in the 2- to 5-year-old age group. "When you say obesity is a matter of personal responsibility, you're saying 2- to 5-year-old children are responsible for their diet and exercise regime. But little children can't be personally responsible for this," he says.
Lustig began looking for underlying causes of obesity while a researcher at St. Jude Children's Research Hospital in Memphis, Tennessee.
"I noticed children with brain tumors tended to develop obesity," he explains. Further research led him to discover that brain tumors sometimes damage the hypothalamus, an area of the brain that controls involuntary functions such as the release of hormones, energy balance and weight gain.
"When the hypothalamus is damaged, it triggers hypothalamic obesity," Lustig says. "People with hypothalamic obesity eat like there's no tomorrow and refuse to move, because their brains think they're starving. This kind of obesity is very difficult to beat."
In continuing his research, Lustig determined that the Western diet can have the same effect on the hypothalamus. While he agrees many factors are at play in today's obesity epidemic, he believes the main culprit is a fairly recent change in the American diet.
The biochemical disorders of obesity
"In the late 1960s, food processors discovered a technique for converting corn – which is grown abundantly and cheaply – into a processed sugar. That new product, high-fructose corn syrup, is a sweetener that affects metabolism in a very negative way," says Lustig.
Fructose is prevalent in countless beverages and processed foods, including juices and fruit drinks, barbecue sauce and ketchup, hamburger buns and pretzels. "While fructose tastes like sugar and is used as a sugar, its biochemical structure is different from sugar, which prevents it from being metabolized or broken down as a sugar," he explains. "It's more like alcohol without the buzz."
As a result, fructose negatively impacts several hormones that are intricately linked to the behaviors – and diseases – associated with obesity. Here are some examples:
Insulin is a hormone secreted by the pancreas to help the body's cells convert glucose to energy. Extra glucose and complex carbohydrates can be converted into a storage compound called glycogen, which is not toxic. On the other hand, fructose is preferentially metabolized into fat. This extra fat goes out into the bloodstream and promotes heart disease. It is also stored in a child's liver and can cause liver disease, much like the cirrhosis of the liver suffered by adults. The damage to the liver causes insulin to skyrocket.
Excess insulin negatively influences leptin, which is a hormone produced by adipose (fat) tissue. Adequate leptin levels inform the brain that it has enough energy to eat and exercise normally. However, when insulin levels are elevated from being overweight or consuming too many refined carbohydrates and sugars, the brain does not recognize leptin's message, inferring a starvation state. This drives the signal to eat more.
In addition, "Excess insulin acts on the brain's reward system, which leads to overeating and makes it hard to stop," explains Lustig. Ultimately, consuming too many refined foods and sugars makes it difficult for the pancreas to produce enough insulin to meet the demand of the body. This causes glucose levels to build up in the bloodstream, which is how diabetes develops.
Lustig summarizes how these biochemical disorders are the root causes of obesity: "The higher your insulin, the more your brain thinks you're starving. The more your brain thinks you're starving, the less you want to exercise and the more you want to eat. This only drives more food intake, which drives your insulin even higher, which interferes with your leptin even more, which makes you think you're starving even more. It's a vicious cycle."
"This is a very different way of looking at obesity," Lustig emphasizes. "While most people blame obesity on a lack of self-discipline, research shows today's foods and drinks actually trigger the behaviors that promote gluttony. Obesity is biochemical, not behavioral."
Lustig's research also explains why young children cannot be held personally responsible for their weight problems and why most obese people have such a difficult time losing weight or keeping it off.
In the article, How to fight – and beat – childhood obesity, Lustig explains why eliminating the biochemical disorders of obesity must be addressed before any weight-loss program can achieve long-term success.
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