Why you really can't resist that piece of cake. . .
US food and drug supremo David Kessler claims that today's fast food is as addictive as cocaine. By Neil Tweedie
Spare a thought for Jamie Oliver. There he is, standing at the foot of the Everest that is American obesity, trying to persuade a nation reared on deep-fried instant gratification to start eating its greens, and all he gets for his trouble is grief.
Our hero is currently to be seen on US network television urging the schoolchildren in Huntingdon, West Virginia, to adopt a healthier diet, in a reprise of Jamie's School Dinners (which was so successful over in Britain that, according to a recent study, the campaign improved SAT results by 4.5pc in the schools where the scheme was first tried).
The result State-side is a mickey-take from David Letterman and a rebuke from a DJ in the rust belt town who has told the meddling Brit to stop infringing the right of freedom-loving Americans to eat themselves to death.
Listen to David Kessler and you will learn that Oliver is up against much more than cultural resistance. The former head of the United States Food and Drug Administration is promoting his new book, in which he describes how our exploding waistlines are due to something much more sinister than greed. The food we eat, or rather the processed, ready-made, fast food we eat, is not really food at all, he says. It's a drug, in its own way as addictive as cocaine.
The three bogeymen Kessler identifies are sugar, fat and salt. Pump the right combination of those ingredients into a dish and you have a winner. The result is something called hyperpalatable food, like a Burger King bacon double-cheese burger or a McDonald's flavoured milkshake. These foods produce increased levels of the neurotransmitter dopamine, which, among other functions, produces in us a sense of reward.
When eating your favourite naughty food you reach what Kessler terms the Bliss Point, that moment during which the cares of the world are banished and replaced by the pure, focused experience of eating. Such foods slip down easily, being "pre-masticated". The roast we used to have to chew 25 times per mouthful has been replaced by processed meat that goes down in 10 chews. It is, in effect, adult baby food.
The brain clocks the pleasure created by the burger and proceeds to build around it a memory, which in turn creates a powerful sense of anticipation, leading to repeat behaviour.
The stimulus drives us to eat long after our calorific and nutritional needs have been satisfied. Old-fashioned hunger simply doesn't come into it. And neither does greed, in the traditional sense of the word.
"We are all wired to be focused on the most salient stimuli around us -- like alcohol, tobacco, sex, gambling," says Kessler. "And what is the most socially acceptable stimulus? Food.
"The basis of the modern food industry is to take fat, sugar and salt and put it on every corner of every street and make it into entertainment. It captures the neural circuits and hijacks the brain. We develop habits around our favourite foods and become aroused when we anticipate them. A pattern develops: cue-activation-arousal-reward. The circuits involved -- memory, learning, motivation, habit -- are those affected by addictive substances or activities.
"I was talking to a guy in publishing who told me how the hardest thing he had to do each day as he travelled to and from work was to get past the news-stand selling KitKats. It wasn't any other kind of candy, it was just KitKats. The news-stand acted a cue; and that red wrapper acted as another cue. He hasn't even eaten the KitKat and he's already stimulated."
Kessler cites the work of Adam Drewnowski, of the University of Washington, who has studied taste and dietary choices for 30 years.
Drewnowski first focused on sugar but soon realised that it alone was not the reason why humans are partial to sweetness -- if it was, we would simply open a packet of sugar and eat it.
The crucial factor was the combination of sugar and fat. In an experiment he added various amounts of sugar to five different dairy products. Asked to choose which foods they liked best, the subjects awarded low marks to products containing sweetened skimmed milk (lots of sugar, little fat) and to unsweetened cream (lots of fat, little sugar). When the same amount of sugar was mixed into low-fat and high-fat products, however, people invariably preferred higher-fat combinations.
Kessler, a paediatrician and former dean of the medical school at Yale University, says the food industry has optimised its products in recent decades.
"They learned to do it by trial and error. They understood that fat, sugar and salt stimulated. They looked at where the long queues were. They designed bliss into the food. You know, that moment at night when you are eating to calm down. You enter a trance-like state in which the stresses of the world disappear. That's because the stimulus is blocking out other traffic."
The more complex the stimulus, the greater the reward. So layering is important, as are packaging and image, adding to the experience, just like with cigarettes. Then there is ubiquity.
"Thirty years ago we ate in meals. There was a structure, as there still is in France. In the United States we have taken down all barriers to eating. You can eat at any time: on the way home from work or school, in your car or at home in the early hours.
"Not only has our diet become dominated by fat, sugar and salt but the hours during which we consume food have expanded. We eat much more chaotically."
Some are more vulnerable than others. A lucky 15pc of us are, for reasons yet to be understood, not interested in food, regarding it more as a necessity than one of life's pleasures.
Others display a common set of characteristics: loss of control in the presence of highly palatable food, an inability to feel full, and a preoccupation with food. This produces "hyper-eating", in which reward centres remain activated until all food on offer has been eaten.
"We are eating not because we are hungry but because we are being stimulated," says Kessler. So what is to be done? What about a drug that switches off our desire for food?
'The trouble is the areas of the brain involved govern lots of other things. You would probably have to lose a couple of IQ points in the process."
"You have to change the way we look at food in the same way that we successfully changed the way we look at tobacco."
Eating, he says, needs to return to structured habits, with set meals and smaller portions. We have to do something, or else face the prospect of millions more children suffering from Type 2 diabetes.
"You know that image of the kid saying 'mommy, daddy, please don't smoke'? We have to get to the point where the kid says 'mommy, daddy, please don't take me to that fast-food restaurant'."
It will be a long journey, admits Kessler.
"Food and sex were the first addictions. It goes very deep."
'The End of Overeating: Taking Control of Our Insatiable Appetite' by David Kessler (Penguin Books)