Britain will be the fat man of Europe within a decade after the largest ever obesity study found that almost four in 10 people will be dangerously overweight by 2025.

For the first time there are more obese people than underweight people in the world as bad diets and lack of exercise combine to create an unstoppable health time-bomb.

Health experts said the crisis in Britain was now a ‘national tragedy’ and blamed the government for failing to bring in higher taxes on sugary foods and drinks.