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Once I was thinking about intensity, I found evidence all around that supported the idea that intensity was the true cause of obesity.

By now I owned a tortoise and two terrapins as well as the original fish, but I fancied something warm blooded. My work schedule ruled out a dog, so I opted for a pair of budgerigars, whom I named Bonnie and Clyde. I now shared a front office with an easygoing guy called Mark, who seemed to be rarely present, and he saw no objection to me keeping caged birds in the corner of our office during the week. I’d never kept budgies before, so I was reading a book called Beginner’s Guide to Budgerigars. I read how to persuade a reluctant budgie to eat up its food:

Soak ordinary seed mix in water for 24 hours. The water triggers off the seeds’ germination and starches are converted to easily digested sugars. Soaked seeds will cause birds to become overweight if fed too often.

This process is eerily similar to the potato processing carried out by McDonald’s—you convert the starches to sugars to enhance the eating experience. 

Obesity is a common problem for caged budgies. In fact, most pet books give advice about not feeding your pet inappropriate food, as most pets can get fat. Cats get fat and so do rats. Scientists like to do obesity experiments on rats, so they need a humane (or perhaps just cheap) method to make rats overeat. They have discovered just the trick—an over-rich diet that, in a laboratory setting, is guaranteed to make rats fat. They call this technique the ‘supermarket diet’.  Feed your experimental rat salami, cheese, chocolate—the contents of a typical lunch box—and she or he will systematically put on weight.

Now that I am lucky enough to work from home, I do have a dog. She is sitting beside me as I type. I am going to do some research on this dog. I have experience doing market research with subjects who can’t speak as I used to work for Fisher Price toys. I just watch their behaviour.

OK, I feel a bit guilty about the animal research I’ve just done, but I don’t think it was bad enough to get my house burned down. I hid a Winalot dog treat in one fist and a similar-sized piece of Mars Delight in the other. By swapping my fists around and allowing the dog to lick through my fingers, I obtained enough data to prove that the Mars product beat the Winalot product hands down. In fact, the dog is giving clear indications that Mars Delight is the best thing she has ever tasted in her life. That is not surprising because that is what we humans said as well.  

Now Masterfoods, the company that makes Mars Delight, are also big in pet food, so should I reveal to them that they have a product that would be a huge motivator in dog training? Or that can give EXTREME pleasure to pet dogs (the experimental dog is now HOWLING for more).

Well, obviously not. The veterinary technologists at Masterfoods animal division do not research food purely for palatability. They want to Prolong Active Life. They care about the well-being of our dogs and cats. If they did try to advertise Mars Delight for dogs, it would be slated by the RSPCA and vets everywhere. (By the way, at 49p, the price would not be a problem—under their Whiskas brand they sell cat milk at 59p for a 200 ml bottle.)  

Yet here is the bizarre thing: when we give chocolate to a child that is normal and kind. We do, literally, feed our children food we do not consider fit for animal consumption.  

When my kids were small, I wheeled them around the supermarket and let them order more or less what they wanted. But I’m not totally irresponsible—I never took my Labrador to the supermarket and let him bark out his choice. What is more, I was careful to explain to my two boys that they should not share their treats with the dog. I explained that his body had not been designed to cope with the high levels of sugar and salt that you find in things like biscuits or crisps. It would be cruel to give him things that his body was not equipped for. I said that, and at the same time I let my children habituate to the unnatural taste of sweets and crisps. Am I so stupid? So inconsistent? Did I think that human babies had evolved to suck on lollipops and munch Hula Hoops? 

No, I’m not stupid. It is just further evidence of my moral cowardice. I was afraid my kids would hate me. I was already the strictest mother on earth for not letting them watch TV before they went to school in the morning. Did I want their school friends to hear that I gave them dog treats rather than sweets when they were good? How can you explain to a five-year-old that Mummy doesn’t believe in Chocolate?

The example of animals fed supermarket diets is a strong argument that Intensity is at the root of obesity. Perhaps even more powerful is the fact that Intensity fits with the spread of obesity, both in terms of time and geography.

Obesity is not a new phenomenon—King Henry VIII had a waist of fifty-four inches in 1545—so there must have been reasons why people got fat in the past. For example, certain medical conditions, such as thyroid gland deficiency or being a eunuch, are known to cause weight gain. Some people are probably ‘designed by their genes’ to be fatter and some skinnier, as with, say, height. Perhaps a psychological trauma can cause an individual to eat in a compulsive or psychotic way. Even centuries ago, there were rich people who had unlimited access to tempting food; some of them were probably greedy slobs and over-indulged in the pleasures of their good fortune.

These are reasons why some individuals got fat in the past. Intensification is an explanation for the fattening of a whole society (a shift of the whole distribution, a mathematician would say).  

Any one individual might be genetically predisposed to being plump. But the genetic makeup of the whole population does not change in fifty years. An individual might be unhappy and eat for comfort. That sort of explanation doesn’t hold for a whole population—unless you believe that unhappiness and comfort eating has systematically increased over time and in all countries that now have an obesity problem. One particular person might be a greedy slob, but the challenge is to explain why half of the nation, in one generation, seemingly became greedy slobs.

Look at the geography and timing: America got fat first. Baskin Robbins started there in 1945; McDonald’s in 1950. America was already rich in the 1960s. As the intense food spread and we got richer in Europe, in Japan, and (more recently) in China and South Africa, obesity became a problem in one region after another. India declared obesity a national emergency in 2006; Mexico is now vying with the US for first place in the obesity stakes.  

Might there be some special ingredient—say those hydrogenated vegetable oils I mentioned before—that causes weight gain? Doctors have looked for such links without finding anything systematic. Artificial fats have been scrutinised, and the trans fats were implicated in heart disease, but doctors can’t seem to find any particular food that causes obesity. The doctors confirm that vegetable fats are extremely fattening, but they are no more fattening than butter and cream. From a medical point of view, pure dairy ice cream is just as fattening as non-dairy ice cream made with hydrogenated vegetable oils.

But doctors are not trained as economists, and it is only from an economist’s perspective that the problem is visible. Non-dairy ice cream is a good deal cheaper. If it tastes so good that ‘you can’t believe it is not butter’ and it costs a quarter of the price, you can afford to eat four times as much.

Many of the foods we eat now were available before: chocolate, butter, fudge. What has changed is the intensity. Food has become so tasty, so cheap, and so available. And the sheer choice—from corn chips to Halva—so titillating, so tempting. There are never enough eating opportunities to savour all the delights on offer.

Some diseases follow genetic routes, some follow infectious vectors (mosquitoes). This one follows technology and wealth. Once people are offered highly intense food and they can afford it, they go for it. How complicated is that?

These patterns in time and geography are probably the strongest evidence that Intensification is the root cause of obesity. We think humans can exercise day-to-day restraint where a Labrador, a budgie, or a rat can’t. Well, most of us simply cannot.

But even so, shouldn’t you stabilise at some level as long as you don’t make the mistake of dieting? However finger-licking tasty the food, homeostasis should reassert itself with your weight stabilising at a higher level. It does in the laboratory rats with the good fortune to be allocated to the ‘supermarket’ test group.

When Faith had explained the diet ratchet to me, I’d seen how it created a perfectly vicious circle that could push your weight up and up. As I thought about intensification, a dreadful new thought crept up on me. I identified another vicious circle, as bitterly ironic as the first. Take a deep breath before you read the next paragraph.

We initially overeat because our diet has become too intense. We are then told that we are getting plump because we eat too much. This is unwelcome news, but we concede that we should cut down the amount we eat. I’m not talking about fasting. We want to stop eating too much so that we don’t keep on getting fatter. So this is what we do: we give up plain, boring food, so that we can keep eating the intense foods that we really would miss. Do you remember the rows I told you about with my mother? We rowed because I rejected her boring dinners, and then I raided the larder. Well, this solved that mystery: my fear of eating too much made me reject her meals, but then I would crack for intense food—for example that twelve-bar mint Aero—simply because I was so hungry.

You sometimes hear people say ‘It’s not worth the calories.’ A food-resisting person will skip food when it is plain (bread, potatoes, vegetables) and save their calories for something ‘Well worth the calories’ or, as often, when they are hungry (having resisted) and they give in to something intense—chocolate, curry, thickly buttered toast. 

I mentioned earlier that two of the girls in my class at junior school were overweight. Diana was one of those two girls. We became friends when we joined the same Girl Guide pack. Sharing a tent at camp, Di told me her horror stories about being overweight. She had been sent to a hospital during the holidays so that doctors could enforce a rigid diet (in other words, hitch Di to the diet ratchet). In hospital she’d been lonely and homesick as well as starved. I shivered in my sleeping bag—is that what they do to people who get fat? I was a talkative and absentminded child and thus no stranger to punishment, but at least I was innocent of that felony and had escaped that degree of torture.

Diana’s mother had briefed Guide Captain about Diana’s condition. Di was to be given smaller portions of everything but the boiled cabbage and was forbidden bacon. In fact, Diana, model slimmer, often ate only half of what she was allowed—at meals. We made up for her sacrifice back in our tent. 

I would buy treats for her at the camp tuck shop. Diana’s family was wealthy and I enjoyed the luxury of buying whatever I (and my new friend) wanted. In this way, Di’s worried mother had achieved a disastrous outcome: she had pushed her daughter’s diet towards the intense foods that Di could buy with her own (lavish) pocket money. Di ate little of the plain food that made up the basic diet of her fellow Girl Guides that week. Her mother was not (on this occasion) doing the ratchet thing, but she was making Diana’s diet more intense. Looking back now, it seems so tragic. Di never stood a chance against the twin forces of starvation and intensification.

It is a massive irony that when people become weight-conscious they make their food environment more intense. Firstly, they move their diet from plain to more intense food as a way of ‘maximising the pleasure per calorie.’ Secondly, they start fooling around with hunger. They resist hunger, often eating little at mealtimes. This will mean that they hit many eating occasions with greater hunger. Hunger is the greatest taste enhancer of all. Food gives you more intense pleasure when you are hungry. The third intensifier is psychological. Psychologically, if you know something is not allowed it becomes more desirable—the forbidden fruit effect.

We use psychological intensification in advertising and selling. Let the consumer know that everyone else is enjoying the product, it is selling out fast, and there won’t be any left for them unless they buy right now. Tell them everyone else is going to enjoy it but not them. Slap on a sticker: ‘90% already sold’ or ‘Offer ends Saturday.’ The idea of deprivation is bizarrely effective—one advertising study demonstrated that showing people diet TV commercials during a film increased their rate of snacking5.

Many dieters say that from the moment they start a diet they think more about fattening food than on a normal day; I’ve heard it called ‘diet brain.’ Some dieters even claim to binge before they start a diet, as they know rich food will soon be banned. The fear of deprivation is itself a powerful intensifier.

Psychological intensification is probably unique to humans. An experimental rat will not fear deprivation or think about calories and greed, so a rat will more quickly recover its natural equilibrium (homeostasis) after starvation. Humans cry because they are fat and because it is so unfair that, because of this, they know they must be deprived. Experimental rats do not cry. Being overweight, ugly, de-sexed, and friendless is probably no big deal for a rodent. Psychologically, we are in a league of our own. (This is similar to Faith’s point about over-intellectualising sex—rats are probably all happy playboys and playgirls too).

These three forces create a new vicious circle—turbo-intensification. It begins with trying to hold yourself back from food, and you start to feel hungry much of the time. When you do finally feel that you deserve some food, you do not want to squander the eating opportunity on boring plain food, you want create a rewarding pleasure occasion by satisfying your intense hunger with intense food—food that has been engineered to precisely hit that appetite spot in your brain6. As you eat (like some famished wolf) you fear you are eating too much, you feel guilty about the foods you most crave, and they seem more attractive than ever. 

Zoologists sometimes amuse themselves by watching animals respond to artificially exaggerated stimuli that they have fixed to the opposite sex—extra long tail feathers or brightly painted spots. Resisting hunger, intense food, and the psychology of deprivation creates a food super-stimulus for humans. Intensity on its own would only make us overweight; it is turbo-charged intensity that drives us to the higher levels of obesity.

Through this process of turbo-intensification, the importance of food can become hugely magnified. It is normal for the mind of a starving person to become totally obsessed with food7; this is an evolutionary survival mechanism, just as much as the slowing metabolic rate. A dieter can arrive at this mental state at the same time as his or her body responds physically to starvation. Through the diet-ratchet and turbo-intensification, food comes to dominate all other pleasures and even all other thoughts.

I had identified a second runaway process (turbo-intensification) that didn’t need calorie-controlled dieting to kick it off. It affects people who are put on diets against their will; they shift to a more intense diet as they make up the missing calories with snacks. It will affect blokes who have put on weight without brutalising their bodies by dieting. They might be clueless about calories but they realise they should resist a bit: ‘Go easy on the ’tats, darlin’, wife’s on at me again about the gut! Oh, no, it’s OK, I’ll still have some of your loverly treacle pudding!‘   

The food industry is sucked into this runaway process. Since they ask us how sweet we like our food, if our taste for sweetness goes up, they will adjust products to our tastes. This is measurable. In 1978 Kellogg’s Special K contained 9.6 g of sugar per 100 g, but this has risen to 17 g today; the amount of sugar in wholemeal bread has gone up by about the same proportion8. This sort of runaway process fits much better with the runaway obesity phenomenon than the idea that we are all getting greedier, more stressed, or more abused each year.

From a start of enjoying intense foods, through a phase of intensifying that pleasure through resisting and guilt, the desire for intense food gets to a level of hankering that, I believe, can fairly be described as addiction. Once the body is habituated to satisfying real hunger with highly intense food—food engineered by the food industry to hit that spot—this puts irresistible pressure on the body’s ability to manage its calorie intake.  


Faith sighed. ‘It seems such a remarkable set of unlucky coincidences…technology improving the taste and availability of food; us resisting and dieting until we become obsessed and addicted, and at the same time our lifestyles become unnaturally sedentary.’  

True. We have a real problem on our hands.

But at last I had the complete new theory in my hands—my replacement for Bath Tub: The Theory of Xtensity. My new theory explained the failure of Bath Tub and explained why I kept putting on weight. All I needed to do now was derive a set of practical, easy-to-follow instructions that would render me permanently slim.


The Theory of