John Harvey Kellogg and his younger brother William invented one of the first breakfast cereals in the 1890s as a health food to aid digestion, but John was furious when William created a version with added sugar.

More than a century later, William’s company, now known as Kellogg, is still at the centre of a conflict between flavour and health. As governments and investors press food companies including Kellogg to make their products more nutritious, the US group has in turn taken legal action against the UK government over an attempt to restrict marketing of some of its cereals because of their sugar content.

The lawsuit is the latest sign of the tensions as governments and investors seek to address a global obesity problem that has been exacerbated by the Covid-19 crisis, even as inflation squeezes consumers’ wallets and intensifies foodmakers’ battle for market share.