It doesn’t make sense to talk about changes to eating habits without bringing in the revolution in what we drink. Perhaps no single change to our diet has contributed more to unthinking excess energy intake than liquids, both soft and alcoholic. We have reached a state where many people, adults and children, can no longer recognise a simple thirst for water, because they have become so accustomed to liquids tasting of something else.
By 2010, the average American consumed 450 calories a day from drinks, which was more than twice as many as in 1965: the equivalent of a whole meal in fluid form. Whether it’s a morning cappuccino or an evening craft beer, a green juice after a workout or an anytime bottle of Coke, the choice of calorific beverages available to us has become immense and varied. Around the world, there are bubble teas and agua frescas; cordials and energy drinks; and then there are all the new-fangled ‘craft sodas’ infused with green tea or hibiscus that pretend to be healthy, even though they probably contain nearly as much sugar as a Sprite. Many modern beverages are better thought of as food than drinks, judging by the number of calories they contain. Yet for reasons both cultural and biological, we don’t categorise most liquids as food. To our bodies, this endless stream of drinks registers as little more satisfying than water.13
Picture a typical day for an average Westerner, and start counting the drinks. It’s a lot. It surprised me to learn that more than 5 per cent of Americans now start the day with a sweetened fizzy drink, but then again, cola for breakfast is a logical enough choice if you work early shifts and don’t have access to a kitchen. A more universal morning drink is coffee, which is often more milk than coffee. Maybe there’s an orange juice on the side. (After decades of growth, however, our appetite for orange juice is finally waning, hit by growing consumer awareness that it is little more than sugar. From 2010 to 2015, the amount of Tropicana fruit juices consumed in the US dropped 12 per cent.) By mid-morning, survey data suggests that 10 per cent of Americans are ready for another coffee or soda. Personally, I am in awe of anyone who waits that long. I am so addicted to coffee, particularly when working, that I am often thinking about my second cup before I have finished the first (which is one of the reasons why I try to take my coffee black as the default. Try).14
And so our days continue, punctuated by sips of sugar-water and caffeine of one kind and another, with or without the addition of milk and various syrups, until the cocktail hour arrives, time for more soft drinks or alcohol. We sometimes imagine that the Mad Men generation of the 1950s were much bigger drinkers than the average person today. But except for a small affluent minority, Americans consumed vastly less alcohol in the 1950s than today – total alcohol intake increased fourfold from 1965 to 2002 in the US.15
This is a global story. A rise in beverage consumption is one of the key elements in the nutrition transition, wherever it has happened. In 2014, a market report on soft drinks wrote of Latin America as ‘the global bright spot for soft drinks brand owners and bottlers’.16 Young people in the emerging economies of Mexico and Argentina drink more of these drinks every year, as incomes increase. In China, people who lived their whole lives drinking nothing but unsweetened tea and water now have access to beer and fizzy drinks and a whole smorgasbord of Starbucks flavoured coffees.
It’s a sign that times are good when you can afford to quench your thirst with liquids other than water. The drinks industry – both soft and alcoholic – has conditioned us to believe that whatever the occasion, it will be improved with a drink in our hand. Studying? An energy drink will help you concentrate. Out with friends? You need a beverage to help you relax. By 2004 the average American was consuming 135 gallons of beverages a year other than water – around one and a half litres a day.17
Wine glasses in England from 1700 to 2017: a sevenfold increase in size (based on an article by Theresa Marteau and colleagues in the British Medical Journal 2017).
It would be easy to paint all this modern beverage consumption as a novel kind of gluttony which those wise great-grandmothers of ours would never have indulged in. But in middle-income countries such as Mexico where much of the water supply is unsafe, buying soft drinks can be a move of self-preservation. Bottled drinks do not contain the bacteria of unclean water and are less likely to make you and your children sick. What’s more, a fizzy drink can look like the frugal choice. Given the option between paying a similar amount for a bottle of water or a bottle of cola, the cola can appear to be better value, because it offers flavouring and energy along with the liquid.
But our biology is not well adapted for this switch to high-calorie beverages. When we talk about what’s wrong with modern drinks, we discuss the problems with sugar, but we don’t talk so much about our own hunger and fullness. It seems that our genes have not evolved to be satisfied by drinking clear liquids, even when those liquids contain as much energy as a three-course lunch. This is the liquid conundrum. A person might easily drink two large glasses of Chardonnay before dinner, and then go ahead and eat a substantial meal as if nothing had happened (or maybe this is just me). Another person might have half a litre of Mountain Dew and feel no less hungry for a foot-long sandwich. With certain exceptions, our bodies simply do not register the calories from liquids in the same way that we do with solid food. This is one of the starkest mismatches between human biology and our current patterns of consumption.
Before the first experiments with honey-wines around 11,000 years ago, the only drinks available to humans were water and breast milk. For most of our evolution as a species, drinks and food were thus two entirely separate things, except for babies. There were survival benefits to keeping the mechanism of thirst separate from the mechanism of hunger. If hunter-gatherers had become full from drinking water, they wouldn’t have felt the need or desire to go out and search for food, and they would have died.18
Numerous studies have shown that most people do not compensate for the energy they drink by eating less. When you drink water, it rapidly enters your intestine, quenching your thirst but doing little to dent your hunger. The same is true even when the water is laced with sugar. It’s as if our bodies simply don’t register the calories in the same way when they arrive from a glass, a cup or a can. Clear fluids such as sports drinks, fruit juices, cola and sweetened iced teas seem to be particularly bad at killing hunger, but milk-based drinks such as lattes and chocolate milk are also surprisingly unfilling for most people, despite the nutrients they contain. Scientific studies show that people have a weak satiety response to clear drinks regardless of how many calories they are laden with – meaning that they don’t fill us up as much as the equivalent calories taken as food. And so we end up consuming a lot more energy from drinks than we intended or even knew.19
As of the year 2000, sugary drinks were the single largest source of energy in American diets. Westerners have been drinking sugar-sweetened tea and coffee for a few centuries, but never before have ‘caloric beverages’ taken up so large a proportion of the average diet. In the past, the largest source of energy in human diets would have been a staple food that actually filled a person up, such as bread. It’s a sign of how disconnected we are from our own hungers that we have reached the point when so many people receive most of their energy from something that gives our stomachs so little satisfaction.
The relationship between liquids and hunger is still not fully understood. One biological explanation for our lack of fullness after a drink is that the normal hormones – peptides – that are triggered in our gut when we eat food are not triggered when we drink sugary or alcoholic drinks. The role of these hormones is to signal to our brains that we are full. When we have a large sugary drink, there is faulty communication between our gut and our brain and somehow we don’t get the message that we have just ingested hundreds of calories.
We need a way to think about liquid-fullness as well as food-fullness. I’ve found it helpful to start telling myself that anything other than water is a snack not a drink: to be savoured, not gulped down. A cappuccino can taste amazingly creamy and delicious when you tell yourself it’s food.