Soda Politics: Taking on Big Soda (and Winning). By Marion Nestle. Oxford University Press; 508 pages; $29.95 and £19.99.

MARION NESTLE’S heavyweight polemic against Coca-Cola and PepsiCo comes at an odd moment for the industry. Americans are drinking fewer sugary sodas—in 2012 production was 23% below what it had been a decade earlier. Even sales of diet drinks are losing their fizz, as consumers question the merits of artificial sweeteners. From one angle, it would seem that health advocates such as Ms Nestle have won. Yet in America companies still produce 30 gallons of regular (not diet) fizzy drinks per person per year. In many countries, particularly developing ones, consumption is on the rise.

Ms Nestle, a professor at New York University, is both heartened by recent progress and dissatisfied with it. That is no surprise. Her first book, “Food Politics” (2002), remains a bible for those who bewail the power of food companies. In her new book she attacks the industry’s most widely consumed, least healthy product. “Soda Politics”, she says, is a book “to inspire readers to action”. As a rallying cry, it is verbose. When readers learn on page 238 that she will pick up a particular subject in chapter 25, it is with no little dismay that they realise they are only on chapter 17. But what the author wants most is to craft a meticulous guide to the producers’ alleged transgressions, and how to stop them.

Ms Nestle says she would have no quibbles with sweet fizzy drinks if they were sipped occasionally, as a treat. However, for millions of people in many countries, they are not. In Mexico companies sold 372 cans of fizzy drinks per person in 2012. About half of Americans do not drink them regularly, but those who do are disproportionately poor, less educated, male, Hispanic or black. Ten per cent of Americans down more than four cans a day.

Drinking a lot of sweet fizzy drinks is plainly unhealthy. Unlike a Big Mac, they have no nutritional value; nor do their calories satisfy hunger. One large study found that for each can added to a person’s daily diet, the risk of diabetes jumped by 22%. There are also links between sugar and heart disease, stroke and cancer. Drinking lots of sodas imposes clear costs on individuals, Ms Nestle argues, but it has a broader cost, too. American taxpayers subsidise corn production (and thereby corn syrup) and let the poor use government food vouchers to buy fizzy drinks. More important, taxpayers foot the health bill for those who develop chronic disease.

Encouraging people to drink fewer fizzy drinks, however, is fiendishly difficult. Soda companies spend billions on marketing; it is a tribute to the admen that Coca-Cola is one of the world’s best-loved brands, despite selling what is essentially fattening sugar-water. (Think of Coca-Cola’s encouragements to “open happiness” and PepsiCo’s exuberant spokeswoman, Beyoncé Knowles.) Once people get used to consuming sugary drinks, they are loth to give them up. There is evidence suggesting that sugar is addictive—some laboratory animals prefer sugar to cocaine.

Most interesting, fizzy-drink companies are skilled at swatting away attempts at regulation. Ms Nestle describes an extraordinarily broad team of allies. That includes obvious friends, such as employees, bottlers and distributors, as well as the restaurants, cinemas, shops and sports stadiums that sell their products. But the companies are also astute philanthropists. When Michael Bloomberg, then mayor of New York, tried to block the use of government vouchers to buy sodas in 2010, the congressional black caucus was among those to lobby against it. The caucus’s foundation has received money from both Coke and Pepsi. In 2011 Philadelphia was considering a soda tax. After the soda lobby offered a big donation to the city’s children’s hospital, the idea fizzled out.

Coca-Cola and PepsiCo do have a few notable adversaries. Mr Bloomberg, a billionaire, remains their single biggest foe. It is telling that in two rare instances when a soda tax has been passed—in Berkeley, California and in Mexico—it was with the help of cash from Mr Bloomberg. Drinks companies must also reckon with a small army of health advocates, among which Ms Nestle is a major-general.

With the slow decline of soda in America, she and her allies are advancing. Coca-Cola and PepsiCo are peddling healthier drinks, such as bottled water. However, as they try to face down a long-term threat while maintaining near-term profits, they are still pushing their syrupy fare.

Ms Nestle is impatient. To the casual reader, her suggestions can seem extreme. She writes enthusiastically about adorning soda cans with warning labels, such as pictures of a diabetic’s foot ulcer. She suggests that parents should teach their children about fizzy drinks by gently boiling down a Coke or a Pepsi into sludge, which sounds rather fun, and asking them to calculate the precise length of grocery shelves bearing sodas, which sounds less so. This zeal threatens to overshadow her stronger points: fizzy drinks offer no nutritional benefit and impose clear costs—on individuals’ health and on society.