The British government on Wednesday outlined plans to ban the sale of high-caffeine energy drinks to children, joining a number of other European countries in a move that it said could cut obesity, reduce anxiety and improve classroom concentration. If it went into effect, the regulation would mean that selling energy drinks containing more than 150 milligrams of caffeine per liter to anyone aged under 16 would be illegal. The ban would apply to all retailers — those selling online and in shops — as well as to restaurants, cafes and vending machines. Sales of tea, coffee and lower-caffeine soft drinks would not be affected, the Health Department said. Around 100,000 British children consume at least one high-caffeine energy drink per day, according to the government, which cited “growing evidence linking these drinks to harmful effects on children, including disrupted sleep, increased anxiety, poor concentration and reduced educational outcomes.”