People who suddenly resort to dieting when in a steady relationship are most likely preparing to dump their other halves, a new study has revealed. Professor Thomas Klein of University of Heidelberg studied the relation between happiness and body weight and said that the warning signs could include a sudden obsession with the gym or getting involved in sports and diets. "When you are on the lookout for a new partner people try to be as thin and attractive as possible," the Daily Mail quoted Klein as saying. Subsequently, when one of the partners in a relationship starts slimming down it can be construed as 'preparing for the partner market'. "People in a relationship feel less pressure and often put on weight as they do not watch their weight so much," he added. "In a happy partnership, people tend to get fat. With less competition, the weight difference is low." But a crisis in a relationship can end the gluttony, he said. And that could result in both partners losing weight. Researchers studied more than 2,000 people aged between 16 and 55. The survey showed that the people in couples generally weighed more than single people hoping to attract a partner in a competitive dating market.