The latest study into the causes of the American obesity epidemic suggests that overeating rather than lack of exercise may be to blame.

The research was presented by Australian scientists at an Amsterdam conference sponsored by the European Association for the Study of Obesity, according to Agence France Press.

AFP quoted study leader Boyd Swinburn from Deakin University as saying American children had grown on average nine pounds heavier over the last 30 years while adults added 17 extra pounds. The scientists’ models showed that a higher calorie intake explains most of the weight gain.

In order to return to the shape the U.S. population was in the 1970s, children would have to reduce their energy intake by about 350 calories a day – an equivalent of one fizzy drink and a small portion of French fries – and adults by about 500 calories, the same as a Big Mac, according to AFP.

Those who are concerned about their weight and its impact on health can choose one of many dietary regimes that may help shed pounds.

The alkaline diet – rich in citrus fruits, vegetables, tubers, nuts and legumes – is one option, and it has the added benefit of boosting bone health into old age.