In ancient times, when food was scarce, our ancestors ate all the food they could get their hands on before it went ‘off’. Researchers believe that when this ‘survival instinct’ kicks in, we automatically seek an energy-rich diet if resources are scarce. This theory is supported by a study in which participants who were given chocolate sweets ate more when confronted by doomsday scenarios. According to researchers, taste was not what caused the reactions, it was a longing for calories. This might go some way to explaining why you find solace in a calorific bar of chocolate or a tub of ice cream when feeling down or faced with hard times.