A university lecturer has coined a new term for one of the key factors driving obesity in the US. 'Portion distortion' is how Brian Wansink of the University of Illinois describes the changing size of restaurant portions. With a quarter of US adults already battling with obesity, nutritionists are examining a range of potential tools to help consumers slim down. These range from prescription and non-prescription weight loss supplements, rigid diets, exercise regimes and lifestyle programmes, but one of the most straightforward ways to help might be cutting portions.