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.

Americans eat out, on average, 30% of the time, so food intake in restaurants and takeaway establishments is crucial to achieving and maintaining a healthy weight.

Portions have certainly got larger over the last few years, and restaurants say they are simply responding to consumer demand for larger portions. As Timothy Weems of the Cheesecake Factory chain said, “Our guests just go, ‘Wow.’ They love our portions.” The group is famed for its big portions – marketing volume and taste. As Weems points out, if customers don’t perceive the offering to be good value, they won’t be back.

Some say the argument comes down to freedom of choice – after all, customers are not obliged to eat everything on their plates. However, a study carried out by the American Institute for Cancer Research showed that 67% of Americans will indeed clear their plate, regardless of the amount of food on it.

A story on NBC also reported on a clear distinction between US and European portion sizes compiled by Self magazine. A portion of US fries generally weighs two ounces heavier than its European counterpart, with nearly 150 more calories. Similarly, a US croissant is twice the weight of a croissant in France, at 4 ounces and 430 calories.

However, American restaurant-goers have one distinct advantage over Europeans. In North America, it is commonplace for diners to take home food they do not eat in a so-called ‘doggie bag.’ The practice is gaining ground in Europe, but is still unusual. Where used, customers can be relieved of the pressure ‘not to waste food’ by having it packed up to enjoy later.