Take fat as an example. Traditionally, fat has been seen as the scourge of the dieter, as it is dense in calories. However, in his research, Dr Sean Lucan says that there is now substantial evidence to suggest that low fat foods like potatoes and white rice are playing a big role in the development of obesity. "Conversely, evidence is mounting to exonerate higher-calorie foods that are rich in fat like nuts, oily fish and olive oil, and even foods high in saturated fat, like dairy products," he says.