NOT all calories put weight on to the same extent – it depends upon the type of food they come from, claim nutritional scientists from the University of Navarra.

They put two groups of people on diets of an equal number of calories, but one group ate almost entirely carbohydrates, whilst the other ate a low-carb, high-fat diet.

The first group, surprisingly, put on more weight than those eating a diet high in fat.

Head of the study, Alfredo Martínez, says that although weight loss and gain is largely genetic, a person's genes can be 'retrained' by the type and quantity of food they eat.