If only we ate less… Yes, it’s actually that simple.

So says a group of researchers, whose recent study, published inthe BMJ (formerly the British Medical Journal), calls forsmaller portions at restaurants andstores.

“The causes of obesity are complex but overconsumption of foodand sugary drinks is a critical proximal determinant, driven inpart by large portion sizes,” writes study author Theresa Marteau,a professor of behavior and health at Cambridge.

The researchers suggest that it is not our appetites that ourdriving larger portions, but rather that larger portions areencouraging us to eat more than we need.

“(P)eople consistently consume more food or non-alcoholic drinkswhen offered larger sized portions or packages, or when usinglarger items of tableware,” states the report.

Marteau points to an economic analysis of obesity last year by the McKinseyGlobal Institute, which found that making portion sizes smaller waslikely the most effective way to reduce obesity and the associatednegative impact it has on public health.

Reducing portions could have a significant effect on Britishcalorie consumption. The report predicts it could reduce intake by12 percent to 16 percent among UK adults.

But the effect would be much more pronounced in the U.S., whosesuper-sized sodas and heaping sides offries have visitors in awe. The report anticipates reducing U.S.portions to 1950’s levels could drop intake by 22 percent to 29percent.

Getting those portions smaller is easier to imagine than toimplement, however. Intervention from government is particularlyhard to do in the U.S., where many are hostile to paternalisticpolicies aimed at limiting the damage we can do to our own bodiesand a number of powerful business interests can be counted on toaggressively fight such restrictions.

The government could also increase awareness of appropriateportions by requiring food packages to more prominently displayinformation about the serving size. The public sector could alsoencourage better habits by serving smaller portions at publicworkplaces, such as schools, hospitals and other governmentbuildings.

“Aligning the will of the public, private industry and politicalleadership is key to progress,” the report concludes.