Experts say fructose, low fibre to blame Sharon Kirkey, CanWest News Service
* * Trans fats may be the health scare du jour but the far bigger twin evils of our food supply are fructose and a lack of fibre, a U.S. child health expert says.
The addition of sugar to foods that once contained none and the removal of fibre have created highly addictive foods that are driving people to overeat, says Dr. Robert Lustig, a professor of pediatrics at the University of California, San Francisco.
He posits fast food, through its effect on insulin, is playing a "key causal role" in why people are getting fatter.
"Itís an insulin nightmare engineered by the food companies."
Insulin suppresses leptin, a hormone produced by fat cells that signals to the brain there is enough energy on board. The more energy, or fat stores, the more leptin. The more leptin, the less likely a person is to reach for a second helping.
The problem with fructose is that it increases the production of insulin, so that people keep eating. Fructose is also bad for what it doesnít do ó suppress ghrelin, the powerful "hunger" hormone.
It explains why, if you order a Pepsi with your burger and fries you would still eat as much as you would without the soft drink because your body doesnít take those extra calories into account.

Fibre controls appetite by keeping insulin down. It also makes food move through the intestine faster, and helps break down fat. Medical anthropologists who dissected stool specimens from people who died in caves 1.5 million years ago estimate early humans once consumed between 100 and 300 grams of fibre a day.
Today, we eat less than 10 grams.
Taken together, the abundance of high-fructose and low-fibre fast foods is leading to central nervous system insulin resistance and obesity, Lustig argues.
"Our pancreases are making double the insulin they did 30 years ago. What about our food has changed our insulin secretion? In 10 words or less? Too much fructose, not enough fibre."
His theory is the latest to try to explain rapid increases in obesity that are spawning everything from airline seatbelt extenders to super-size folding beach chairs, swimwear in size 70 and "telescoping" scrubbers for people who can no longer bend over to clean the bathtub.
For the first time in human history, there are more over-nourished people than there are undernourished.
In Canada, obesity among adults has nearly doubled since 1978, to 23 per cent in 2004, according to Statistic Canada.
Obesity rates among children are rising even faster: 28 per cent of children are now overweight or obese.
Doctors at Torontoís Hospital for Sick Children are treating four- and six-year year olds with high cholesterol because of their weight. Montrealís Royal Victoria Hospital is performing bariatric bypass surgery ó or "stomach stapling" ó on adults so massive, it takes three nurses and an orderly to move them from the operating table onto a gurney.
Some argue obesity boils down to unhealthy or "pathological" behaviour on the part of the fat person. "People go to a doctor and say, why am I fat? And the doctor says youíre a glutton and a sloth. You eat too much and you exercise too little."
Lustig says. But he argues few people, if any, choose to be obese ó and certainly not children ó and that there is a physiological underpinning to "gluttony and sloth."
Humans evolved to survive starvation, not to resist extra-cheesy deep-dish pizzas and bacon double cheeseburgers. Our hunter-gatherer ancestors sought out energy-dense foods high in fat, starch and sugar.
Those who survived the seven-year famine "were the greedy ones who got a little bit fat beforehand", says Dr. Steve Bloom, head of the division of investigative science at Imperial College London.
"The ones who werenít greedy and didnít grab the last crust of bread were the ones who died, and therefore their genes are no longer in our gene pool," Bloom said in an interview.
The problem today, Bloom wrote in an article in New Scientist, is food "is freely available and the good times just keep on rolling."
"The odd thing is that we are not fatter," Bloom says. "Most people only maintain their weight by conscious and continuous restraint."
So is there any alternative to a life of frugal eating? After eating a meal, the gut produces hormones that tell the brain "weíve got enough food in the machinery, donít eat anymore," Bloom explained. In small experiments, he has shown that overweight human volunteers who injected themselves three times a day for four weeks with one of these hormones ó oxyntomodulin ó lost 2.3 kg compared to 0.5 kg in the "control" group that was unknowingly injecting saline.
"Thatís about half a kilogram a week, and thatís a very high rate of weight loss, much higher than any other medication available on the market or being market," says Bloom.
But Lustig argues the answer to the obesity crisis isnít hoping science will one day find a way to tinker with neurons and hormones that control hunger and appetite.
Just this month, Merck announced itís experimental anti-obesity drug known as MK-0557 failed to produce clinically meaningful weight loss in obese people.
Patients taking the drug for a year lost only a little more than one kilogram more than those on a placebo. One Merck researcher acknowledged it will likely take not a single drug, but a cocktail of drugs, to unwire the human food intake system, and that the struggle isnít unlike "sending the space shuttle into orbit."
Nor are behaviour and/or lifestyle modifications successful in the majority of obese children, and long-term success rates are even worse in adults
"Why do you think there are so many programs? Because none of them work consistently," Lustig says. "The only thing that works is vigorous exercise of 60 to 90 minutes every day. Those people lose, and keep it off. Everyone else gains it back."
Which brings us back to what Lustig calls the "smoking gun" in the obesity wars: Insulin.
Normally, when sugar is turned into fat, the fat cells make leptin, the "Iím full hormone" that tells the brain to reduce food intake, and reduce insulin.
But insulin antagonizes, or interferes with, leptin. If the brain canít see leptin it thinks the body is starving. The body is catapulted into starvation mode as it tries to conserve energy, leaving people feeling hungry and lethargic.
Leptin and insulin also appear to regulate our "hedonic" responses to food by acting on the brainís reward centre, the same part of the brain that responds to drugs of abuse such as nicotine and morphine.
Insulin blunts the "reward" of food in rats, but too much insulin appears to increase the pleasure we get from eating.
Rats with high insulin experience "unchecked caloric intake": Even if they were just fed, they would eat again if given something palatable.
Sweet and affordable high-fructose corn syrup has become the most common sweetener used in commercially prepared foods. Itís found in items ranging from soft drinks and chocolate bars to crackers, ketchup, sauces and buns. Average daily fructose consumption has increased by more than 25 per cent over the past 30 years.
A recent study found rats fed fructose gained weight and developed insulin resistance without eating more calories.
Lustigís theory ó based on a review of nearly 100 studies ó is controversial, but his work was published in August in the journal, Nature Clinical Practice Endocrinology and Metabolism, and his reasoning fits with trends in fructose consumption.
Canadians each consume 95.2 litres of soft drinks per year, or nearly 270 cans of pop.
Today, one-quarter of Canadians will eat something in a fast-food outlet. Among teens aged 14 to 18, a third will eat fast food.
Lustig admits that common wisdom says obesity is a combination of genetics and environment. But our gene pool has not changed in the last 30 years.
Meanwhile, 10 to 15 per cent of the adult population in Canada is now morbidly obese. Even people at the lower end of the BMI curve are gaining weight.
Says Lustig, "Whatever is happening, is happening to everyone."

© CanWest News Service 2006