Kitabı oku: «First Bite: How We Learn to Eat», sayfa 2

So we cannot assume that everyone who is ‘normal weight’ has a healthy relationship with food. (Incidentally, given that these people are in a minority, isn’t it time we stopped calling them ‘normal’? How about ‘exceptional’ instead?) The situation is more complicated than the numbers suggest. But I’d still hazard that this exceptional third of the population has something important to tell us. There are hundreds of millions of individuals who somehow swim against the tide of the dysfunctional modern food supply and feed themselves pretty well. There are those who can eat an ice-cream cone on a hot day without needing to punish themselves for being ‘naughty’; who automatically refuse a sandwich because it isn’t lunchtime yet; who usually eat when they are hungry and stop when they are full; who feel that an evening meal without vegetables isn’t really a meal. These individuals have learned the eating skills that can protect them in this environment of plenty.

Viewed through the lens of behavioural psychology, eating is a classic form of learned behaviour. There is a stimulus – an apple tart, let’s say, glazed with apricot jam. And there is a response – your appetite for it. Finally, there is reinforcement – the sensory pleasure and feeling of fullness that eating the tart gives you. This reinforcement encourages you to seek out more apple tarts whenever you have the chance and – depending on just how great you feel after eating them – to choose them over other foods in the future. In lab conditions, rats can be trained to prefer a less sweet diet over a sweeter one when it is packed with more energy and therefore leaves them more satisfied: this is called post-ingestive conditioning.²²

We know that a lot of this food-seeking learning is driven by dopamine, a neurotransmitter connected in the brain with motivation.²³ This is a hormone that is stimulated in the brain when your body does something rewarding, such as eating, kissing or sipping brandy. Dopamine is one of the chemical signals that passes information between neurons to tell your brain that you are having fun. Dopamine release is one of the mechanisms that ‘stamps in’ our flavour preferences and turns them into habits. Once animals have been trained to love certain foods, the dopamine response can be fired up in the brain just by the sight of them: monkeys have a dopamine response when they see the yellow skin of bananas as they anticipate the reward.²⁴ Anticipating dopamine release is the incentive that makes lab rats work hard for another treat by pressing a lever.

Humans, needless to say, are not lab rats.^fn2 In our lives, the stimulus–response behaviour around food is as infinitely complex as the social world in which we learn to eat. It’s been calculated that by the time we reach our eighteenth birthday, we will have had 33,000 learning experiences with food (based on five meals or snacks a day).²⁵ Human behaviour is not just a clear-cut matter of cue and consequence, because human beings are not passive objects, but deeply social beings. Our conditioning is often indirect or vicarious. We do not just learn from the foods we put in our own mouths, but from what we see others eat, whether in our own families, at school or on TV.

As children watch and learn, they pick up many things about food besides how it will taste. A rodent can press a lever to get a sweet reward, but it takes an animal as strange and twisted as a human being to inject such emotions as guilt and shame into the business of eating. Before we take our first bite of a certain food, we may have rehearsed eating it in our minds many times. Our cues about when to eat and what to eat and how much extend beyond such drives as hunger and hormones into the territory of ritual (eggs for breakfast), culture (hotdogs at a baseball match) and religion (turkey at Christmas, lamb at Eid).

It soon became clear to me that I could not get the answers I sought about how we learn to eat without exploring our wider food environment, which is a matter of mealtimes and cuisine, parenting and gender as well as neuroscience.

Our modern food environment is fraught with contradictions. The burden of religious guilt that has been progressively lifted from our private lives has become ever more intense in the realm of eating. Like hypocritical temperance preachers, we demonize many of the things we consume most avidly, leaving us at odds with our own appetites. Numerous foods that were once reserved for celebrations – from meat to sweets – have become everyday commodities, meaning not only that we over-consume them but that they have lost much of their former sense of festal joy.²⁶ The idea that you don’t eat between meals now seems as outdated as thinking you must wear a hat when you step out of the house.

Yet while the nutritional content of our food supply has changed hugely over the past fifty or so years, other aspects of eating have not changed fast enough to keep pace with modern life. Parents are still using a range of traditional feeding methods – such as urging children to finish what’s on their plate – that were devised for a situation where famine was always round the corner. As we’ll see, such feeding techniques are directly contributing to child obesity, in cultures as diverse as China and Kuwait.

The theme I returned to more than any other was families. Most of what we learn about food happens as children, sitting at the kitchen table (if your family is lucky enough to have one), being fed. Every bite is a memory and the most powerful memories are the first ones. At this table, we are given both food and love, and we could be forgiven if, later in life, we have trouble distinguishing the two. It is here that we develop our passions and our disgusts and get a sense of whether it is more of a waste to leave something on the side of the plate or to eat it up when we are not hungry.

Our parents – like governments – hope we will learn about food from the things they tell us, but what we see and taste matters more than what we hear. In many ways, children are powerless at the table. They cannot control what is put in front of them, or where they sit, or whether they are spoken to kindly or harshly as they eat. Their one great power is the ability to reject or accept. One of the biggest things many children learn at that table is that our choice to eat or not eat unleashes deep emotions in the grown-ups close to us. We find that we can please our parents or drive them to rage, just by refusing dessert. And then the adults complain that we are difficult at mealtimes!

After a certain point in our lives, it is us and not our parents spooning food into our mouths. We discover the glorious liberation of being able to choose whatever we want to eat – budget permitting. But our tastes and our food choices are still formed by those early childhood experiences. Rather alarmingly, it seems that our food habits when we were two – whether we played with our food, how picky we were, the amount of fruit we ate – are a pretty accurate gauge of how we will eat when we are twenty.²⁷

The acquisition of eating habits is a far more mysterious skill than other things we learn in childhood, such as tying our shoelaces, counting or riding a bike. We learn how to eat largely without noticing that this is what we are doing. Equally, we don’t always notice when we have learned ways of eating that are dysfunctional, because they become such a familiar part of ourselves. Having particular tastes is one of the ways that we signal to other people that we are unusual and special. We become known as the person in the family who adores munching on bitter lemon rind or the one who eats apples right down to the pips.

You might say that food dislikes do not matter much: each to their own. I won’t give you a hard time for hating the fuzzy skin of peaches if you will excuse my squeamishness about the gooey whites of soft-boiled eggs. The danger is when you grow up disliking entire food groups, leaving you unable to get the nutrition you need from your diet. Doctors working at the front line of child obesity say it has become common in the past couple of decades for many toddlers to eat no fruit and vegetables at all. This is one of the reasons constipation is now such a huge – though little mentioned – problem in Western countries, giving rise to 2.5 million doctor visits a year in the US.²⁸

Some hold the view that it doesn’t really matter if children have unhealthy tastes, because once they grow up they will effortlessly acquire a penchant for salad, along with a deeper voice and mature political opinions. Sometimes it does work out this way. Love and travel are both powerful spurs to change. In the 1970s it was a common rite of passage to reject the conventional bland watery foods of a 1950s childhood and embrace mung beans and spice. Many tastes – for green tea, say, or vodka – are acquired, if at all, in adulthood. When we learn to love these bitter but lovely substances, we undergo what psychologists call a ‘hedonic shift’ from pain to pleasure.²⁹ You may overcome your childish revulsion at the bitterness of espresso when you discover the wonderful after-effects, how it wakes up your whole body and infuses you with a desire for work. The great question is what it takes for us to undergo a similar ‘hedonic shift’ to enjoying a moderate diet of healthy food.

The process will be different for each of us, because all of us have learned our own particular way of eating. But wherever you start, the first step to eating better is to recognize that our tastes and habits are not fixed but changeable.

There’s a danger here that I’m making the process of changing how you eat for the better sound easy. It isn’t. In particular, it isn’t easy for those who feed themselves on a tight budget. Many have observed that – in developed countries – obesity disproportionately affects those on low incomes. Poverty makes eating a healthy diet harder in numerous ways. It’s not just because it is far more expensive, gram for gram, to buy fresh vegetables than it is to buy heavily processed carbohydrates. Maybe you live in a ‘food desert’ where nutritious ingredients are hard to come by; or in housing without an adequate kitchen. Growing up poor can engender a lifetime of unhealthy food habits, because a narrow diet in childhood is likely to narrow your food choices as an adult, even if your income later rises. When the flavour of white bread and processed meat are linked in your memory with the warmth and authority of a parent and the camaraderie of siblings, it can feel like a betrayal to stop eating them.

Yet it’s striking that some children from low-income households eat much better than others, and sometimes better than children from more affluent families. The problems with how we eat now cut across boundaries of class and income. It is feasible to create decent, wholesome meals – bean goulash, spaghetti puttanesca – on a shoestring budget. Equally, one can have the funds to buy chanterelle mushrooms and turbot but no inclination to do so. According to feeding therapists with whom I have spoken, there are successful business people who will – literally – pass out from hunger at their desks rather than allow an unfamiliar meal to pass their lips when their preferred junk food is not available. Assuming you are not living in a state of famine, the greatest determinant of how well you eat is the way you have learned to behave around food.

This behaviour is often immensely complex. As we grow up, we become capable of second order preferences as well as first order preferences. A first order preference is basic: you love crispy roast potatoes, smothered in butter and salt. A second order preference is more convoluted: you want to like eating carrots instead of the potatoes because you think they would be less fattening and healthier. Indeed, you probably can, at least sometimes, limit yourself to eating raw vegetables instead of the carb-laden potatoes. But the real question is what happens next. In 1998 the social psychologist Roy Baumeister did a famous experiment. Baumeister, who is known for his work on self-defeating behaviours, found that the struggle of will required when a group of people were asked to eat ‘virtuous’ foods such as radishes instead of the foods that they really wanted, such as chocolate and cookies, led to diminishing returns.³⁰ They were so depleted by the effort of the task that when faced with another difficult task – solving a tricky puzzle – they would give up more quickly. The emotional effort of not eating the cookies had a ‘psychic cost’.

Changing our food habits is one of the hardest things anyone can do, because the impulses governing our preferences are often hidden, even from ourselves. And yet adjusting what you eat is entirely possible. We do it all the time. Were this not the case, the food companies who launch new products each year would be wasting their money. After the fall of the Berlin Wall, housewives from East and West Germany tried each other’s food products for the first time in decades. It didn’t take long for those from the East to realize that they preferred Western yoghurt to their own.³¹ Equally, those from the West discovered a liking for the honey and vanilla wafer biscuits of the East. From both sides of the wall, these German housewives showed a remarkable flexibility in their food preferences.

There is hope as well as concern in the fact that we remain like children in our eating patterns. We are like children in our fussiness and love of junk. But we also remain like children in that we have a capacity to learn new tricks, one that we seldom credit ourselves with. Even though most of us have tastes acquired very young, we can still change.

When I was a teenager I could eat whole pint-sized tubs of ice cream, and second and third helpings of everything. Everywhere I went, food screamed at me. Maybe it was a response to living with my older sister, who was anorexic, though this was never mentioned, because in our family we did not speak of such things. Or it could have been a consequence of growing up in a house where emotional talk was taboo. It definitely got worse when I was fourteen and my parents separated. Overeaters often say they are swallowing their feelings.

Around the age of twenty, something changed. I fell in love, got happier and my meals became more structured. I shrank from large to medium, without ever particularly dieting. I ate lots of vegetables, not because I had to, but because they were delicious, and they made me feel good. Then I had children. I could now bake a whole chocolate cake, eat a small slice and leave the rest. Recently I discovered yoga. My teenage self would have found my current self intensely annoying.

The strange thing, however, is that my behaviour changed without me ever particularly noticing that this was what was happening. Unlike the adolescent diets that I imposed on myself in a conscious, self-correcting way, this new healthier life crept up on me unawares. It’s not that I never carry on eating crisps long after I am full, especially when there’s a glass of wine in my hand. I may be safe around chocolate cake, but I wouldn’t fancy my chances with a Vacherin Mont d’Or cheese in the kitchen. But I have definitely reached the point where my second order food preferences – I want to like greens – and my first order food preferences – I do like greens – are fairly in sync. Food no longer screams but speaks to me. It helps that our concept of healthy eating has enlarged in recent years to take in satisfying meals such as chicken and chickpea soup, buckwheat pancakes, avocado toast or buttery scrambled eggs with herbs. I’m in the groove now of eating smaller lunches and larger dinners, but small or large, meals are occasions for pleasure, not angst. This feels good. I must have relearned how to feed myself somewhere along the way, treating myself with some of the solicitude I bestow on my children.

E.P. Köster, a behavioural psychologist who has spent decades studying why we make the food choices we do, says that food habits ‘can almost exclusively be changed by relearning through experience’.³² That is, if we want to relearn how to eat, we need to become like children again. Bad food habits can only change by making ‘healthy food’ something pleasure-giving. If we experience healthy food as a coercion – as something requiring willpower – it can never taste delicious.

It’s seldom easy to change habits, particularly those so bound up with memories of family and childhood, but, whatever our age, it looks as if eating well is a surprisingly teachable skill. This is not to say that everyone should end up with the same tastes. Life would be dull if everyone preferred satsumas to clementines. But there are certain broad aspects of eating that can be learned and then tailored to your own specific passions and needs. There are three big things we would all benefit from learning to do: to follow structured mealtimes; to respond to our own internal cues for hunger and fullness rather than relying on external cues such as portion size; and to make ourselves open to trying a variety of foods. All these three can be taught to children, which suggests that adults could learn them too.

For our diets to change, as well as educating ourselves about nutrition – and yes, teaching ourselves to cook – we need to relearn the food experiences that first shaped us. The change doesn’t happen through rational argument. It is a form of reconditioning, meal by meal. You get to the point where not eating when you are not hungry – most of the time – is so instinctive and habitual it would feel odd to behave differently. Governments could do a great deal more to help us modify our eating habits. In place of all that advice, they could reshape the food environment in ways that would help us to learn better habits of our own accord. A few decades from now, the current laissez-faire attitudes to sugar – now present in 80 per cent of supermarket foods – may seem as reckless and strange as permitting cars without seatbelts or smoking on aeroplanes.³³ Given that our food choices are strongly determined by what’s readily available, regulating the sale of unhealthy food would automatically make many people eat differently. Banishing fast-food outlets from hospitals and the streets surrounding schools would be a start. One study shows that you can reduce chocolate consumption almost to zero in a student cafeteria by requiring people to line up for it separately from their main course.³⁴

But at an individual level, we won’t achieve much by waiting for a world where chocolate is scarce. The question is what it might take to become part of that exceptional third (give or take) of the population who can live in the modern world, with all its sugary and salty allurements, and not be agonized or seduced. Having a healthy relationship with food can act like a life jacket, protecting you from the worst excesses of the obesogenic world we now inhabit. You see the greasy meatball sandwich and you no longer think it has much to say to you. This is not about being thin. It’s about reaching a state where food is something that nourishes and makes us happy rather than sickening or tormenting us. It’s about feeding ourselves as a good parent would: with love, with variety, but also with limits.

Changing the way you eat is far from simple, but nor, crucially, is it impossible. After all, as omnivores, we were not born knowing what to eat. We all had to learn it, every one of us, as children sitting expectantly, waiting to be fed.

CHAPTER 1:
Likes and Dislikes

Every man carries within him a world, which is composed of all that he has seen and loved, and to which he constantly returns, even when he is travelling through, and seems to be living in, some different world.

FRANÇOIS-RENÉ DE CHATEAUBRIAND, Travels in Italy, 1828

‘He won’t eat anything but cornflakes,’ complained the mother of a boy I used to know. Breakfast, lunch or dinner – always a bowl of cornflakes and milk. Even at other people’s houses, this boy made no concessions. To his mother, his extreme diet was a source of worry and exasperation. To the rest of us, he was a fascinating case study. Secretly, I was slightly in awe of him; my sister and I would never have dared be so fussy. To look at, you wouldn’t know there was anything different about this kid: scruffy blond hair, big grin, neither unduly skinny nor chubby. He was not socially withdrawn or difficult in any other way. Where did it come from, this bizarre cornflake fixation? It just seemed to be part of his personality, something no one could do anything about.

Whether you are a child or a parent, the question of ‘likes and dislikes’ is one of the great mysteries. Human tastes are astonishingly diverse, and can be mulishly stubborn. Even within the same family, likes vary dramatically from person to person. Some prefer the components of a meal to be served separate and unsullied, with nothing touching; others can only fully enjoy them when the flavours mingle in a pot. There is no such thing as a food that will please everyone. My oldest child – a contrarian – doesn’t like chocolate; my youngest – a conformist – adores it. It’s hard to say how much of this has to do with chocolate actually tasting different to each of them and how much it has to do with the social pay-off you get from being the person who either likes or loathes something so central to the surrounding culture. The one who loves chocolate gets the reward of enjoying something that almost everyone agrees is a treat. And he gets a lot of treats. The one who doesn’t like chocolate gets fewer sweets, but what he does get is the thrill of surprising people with his oddball tastes. He fills the chocolate-shaped void with liquorice.

Yet my chocolate-hating boy will happily consume pieces of chocolate if they are buried in a cookie or melted in a mug of hot cocoa. One of the many puzzles about likes and dislikes is how they change depending on the context. As the psychologist Paul Rozin says: ‘to say one likes lobster does not mean that one likes it for breakfast or smothered in whipped cream.’¹ Different meals, different times of day and different locations can all make the same food or drink seem either desirable or not. Call it the retsina effect: that resinated white wine that is so refreshing when sipped on a Greek island tastes of paint-stripper back home in the rain. It’s also worth remembering that when we say we like this or that, though we use the same words, we are often not talking about the same thing. You may think you hate ‘mango’ because you have only ever tasted the fibrous, sour-yellow kind. When I say I adore it, I am thinking of a ripe Alphonso mango from India, brimming with orange juice and so fragrant you could bottle it and use it for perfume.

The foods we eat the most are not always the ones we like the most. In 1996 the psychologist Kent Berridge changed the way that many neuroscientists thought about eating when he introduced a distinction between ‘wanting’ (the motivation to eat something) and ‘liking’ (the pleasure that the food actually gives).² Berridge found that ‘wanting’ or craving was neurally as well as psychologically distinct from ‘liking’. Whereas the zone of the brain that controls our motivation to eat stretches across the entire nucleus accumbens, the sections of the brain that give us pleasure when we eat occupy smaller ‘hotspots’ within this same area. For Berridge, this discovery offers a fruitful way for thinking about some of the ‘disorders of desire’ that bedevil humans. For example, binge eating may – like other addictive behaviours – be associated with ‘excessive wanting without commensurate “liking”’.³ You may feel a potent drive to purchase an extra-large portion of cheesy Nachos even though the pleasure they deliver when you actually consume them is much less potent than you expected. Indeed, binge eaters often report that the foods they crave do not even taste good when they are eating them: the desire is greater than the enjoyment.

However, several neuroscientists have pointed out in response to Berridge that liking and wanting remain ‘highly entangled’.⁴ Berridge himself admits that there is strong evidence that if you reduce the amount a food is liked, the consequence is that it is also wanted less.⁵ Even if our craved foods do not make us as happy as we hope they will, the reason that we crave them in the first place is because we once loved them.⁶ Like drug addicts, we are chasing a remembered high. Our ‘likes’ thus remain a central motivating force in shaping how and what we eat. To find out more about why we like the foods we do remains a vital question for anyone who is interested in feeding themselves or their family better. If asked to say where tastes come from, I suspect that most of us would say they were determined by individual temperament, which is another way of saying ‘genes’. Being a chocolate lover – or hater – becomes so much part of our self-image that we can’t imagine ourselves any other way. We show that we are adventurous by seeking out the hottest chillis; we prove we are easy-going by telling our host we ‘eat anything’. We confirm that we are naturally conservative by eating patriotic hunks of red meat. Taste is identity. Aged eight, my daughter used to draw pictures of herself and write ‘prawns-peas-mushrooms’ at the top, surrounding herself with the tastes she loved best.

Because our tastes are such an intimate part of ourselves, it is easy to make the leap to thinking that they must be mostly genetic: something you just have to accept as your lot in life. Parents often tell children that their particular passions place them on this or that side of the family – you got your fussiness from your grandfather! – as if you were destined from birth to eat a certain way. Sometimes it is uncanny how a suspicion of celery or a deep hunger for blackberries replicates from parent to child. When we notice these familial patterns, it confirms us in our view that food preferences must be inherited through our genes.

When I’ve described the argument of this book to people I meet, sometimes they get a little angry. ‘I disagree that we learn how to eat,’ they say. ‘You’d never get me to like sultanas/squid/salami [delete as appropriate].’ Anyway, they say, ‘What about genes?’

It’s fine by me if you don’t like sultanas. And I’m certainly not denying that there is a genetic component in our relationship with food. We are not born as blank slates. Some people have a heightened genetic sensitivity to certain flavours (notably bitterness) while others are blind to them.⁷ There are also genetic variations in individual appetite, the speed at which we eat and the extent to which people actually enjoy eating.⁸ We vary in how we chew, how we swallow and how we digest. Some people are born with conditions that make it much harder to eat, such as a delay to the oral-motor system. I had no idea quite how fraught the basic matter of getting food from plate to mouth could be until my third child was born with cleft palate and he and I both struggled at mealtimes. He is now five and new dishes occasionally still provoke tears (usually his). Our relationship with food and weight is additionally affected by epigenetics: our experience in the womb. The ‘thrifty phenotype’ hypothesis of biochemist C. Nicholas Hales and epidemiologist David Barker suggests that being undernourished in utero leaves people with a lifelong propensity for weight gain, an unfair fate to be handed so early.⁹

The question remains to what extent we are capable of overriding this genetic and epigenetic inheritance and learning new tastes. This riddle can seem impossible to unravel, given that children do not learn to eat under laboratory conditions. As we take our first bites, our parents are supplying us simultaneously with both nature (genes) and nurture (environment conceived in its broadest sense, including everything from cuisine to family dynamics to religion to cutlery and table manners to the ethics of meat to views on whether it’s OK to eat food off the floor if it was only there for five seconds). The two are so intertwined, it’s hard to tell where one starts and the other stops.

In one remarkable experiment, however, a group of children did learn to eat under lab conditions. In the 1920s and 1930s, Dr Clara Davis, a paediatrician from Chicago, spent six years trying to study what children’s appetites would look like if allowed to blossom in total freedom without any preconceived ideas of what tasted good.¹⁰ Davis’s results have often been taken as a clear indication that likes and dislikes are fundamentally inbuilt and natural though, as we’ll see, Davis herself drew a rather different conclusion.

In 1926, at Mt Sinai Hospital in Cleveland, Dr Clara Marie Davis started the most influential experiment ever conducted into the question of human likes and dislikes. As a doctor, Davis saw many children with eating problems – mostly refusal to eat – whose appetites did not match their nutritional needs. She wondered what children’s appetites would look like, freed from the usual pressures of parents and doctors pushing them to eat nutritious foods such as hot cereal and milk, regardless of whether they liked them. Conventional medical wisdom at that time was that children’s particular likes should not be indulged, lest they became ‘faddy’. Dr Davis was not so sure that eating what you liked was automatically a bad thing.

She borrowed a number of infants – some of them orphans from institutions and some the children of teenage mothers and widows – and placed them on a special ‘self-selection diet’ under her medical care. The children – aged from six to eleven months, who had never yet tasted solid food – were offered a selection of whole, natural foods and given free rein, day after day, to eat only what they wished. The full list of foods was: