Empty calories

“Empty calories” is an everyday term for foods that provide lots of energy but almost no vitamins, minerals, fibre or high-quality protein. Classic examples are fizzy drinks, energy drinks, sweets, crisps, white-flour baked goods and alcohol. The more scientific way to put it: foods with a low nutrient density.

Why is that a problem? Your body has a fixed energy requirement, but also a fixed nutrient requirement. If you get 500 kcal a day from fizzy drinks and gummy bears, you have 500 kcal less “room” for foods that bring iron, calcium, vitamins and fibre with them – or you eat on top of that and gain weight. What's more, empty calories aren't very filling, because they lack volume, protein and fibre.

For adults, alcohol belongs in this category too: one gram provides 7 kcal, almost as much as fat. Half a litre of beer has around 200 kcal, a glass of wine about 150 – and on top of that, alcohol slows down fat breakdown, because the liver deals with it first. The German Nutrition Society (DGE) now recommends avoiding alcohol altogether if possible.

That doesn't mean sweets or snacks are off-limits. A tried-and-tested rule of thumb for adults: around 10% of your daily energy can be “treat calories” – at 2,000 kcal, that's about 200. That's a chocolate bar or a small handful of crisps. Enjoyed mindfully, without a guilty conscience, and not on autopilot in front of a screen.

With children, it's worth making sweet treats a fixed, predictable part of the day – an afternoon portion, for example – rather than banning them or using them as a reward. Bans only make sweets more desirable.