Kit Kats and Oreos will become healthier, the government will say on Saturday, announcing that the companies making them have signed up to a "responsibility pledge" to cut the saturated fat the products contain. But the sugar levels in them will stay the same.

Days after the British Medical Journal ran an opinion piece from a cardiologist asserting that sugar and not saturated fat was the leading cause in the rise in heart disease and diabetes, the government announced the latest in its series of public health pledges with food manufacturers and supermarkets. This will, ministers say, remove the equivalent of one-and-a-half Olympic-sized swimming pools full of saturated fat from the national diet.

Tesco says it will remove 32 tons of fat out from its breadsticks and other products, while Morrisons promises to reformulate its own-brand range of spreads to take out some of the saturated fats, amounting to another 50 tons. The U.K.’s Sainsbury’s Supermarkets Ltd. says it will continue work it has begun in reducing the saturated fat in its products. Mondelez International, the snack arm of Kraft, says it will reformulate products including belVita and Oreo cookies.

Saturated fat was blamed for growing rates of heart disease and diabetes in the 1970s, following the landmark "seven countries" study by American scientist Ancel Keys. However, the British physiologist John Yudkin disagreed with what became the conventional public health wisdom, arguing that the problem was sugar. Yudkin's cause has been taken up again in recent years, notably by the U.S. pediatrician Robert Lustig, in his book, Fat Chance: The Bitter Truth About Sugar.

Lustig and others argue that the low-fat craze may have actually done harm to people's health because food manufacturers add sugar into low-fat products to compensate for the loss of taste and texture after the fats are removed.