Close to a quarter of the young men called up for their compulsory military service each year are overweight, according to the findings.

Of these, six percent are obese, with a body mass index (BMI) above 30.

The index is calculated by dividing a person’s weight in kilogrammes by the square of his height in metres.

“For around a dozen years, conscripts have had more problems with weight,” Frank Rühli, director of the Institute of Anatomy’s Centre for Evolutionary Medicine, is quoted as saying by 20 Minutes online.

In 2012, 672 young men were declared unsuitable for the Swiss army because they were too fat, the newspaper reported

Recruits with a BMI over 30 are only accepted if they have a minimum level of physical fitness, the military medical service says.

The army no longer has the right to accept recruits with a BMI over 40, the service says.

The problem of overweight soldiers has also hit the officer ranks, 20 Minutes said.

Those with a BMI above 30 are required to have compulsory interviews to review ways to get into shape.

A new study by the University of Zurich’s Centre for Evolutionary Medicine shows that average Swiss resident has grown considerably since the late 19th century.

The average body height increased by 15 centimetres from residents born in the 1870s to those born in the 1970s, says the study, published this month in General and Comparative Endocrinology, a scientific journal.

Since the 1970s, the Swiss “body shape” has evolved from growth in height to “growth in breadth”, the study, based on detailed data from military records shows.

Widespread iodine deficiency at the end of the 19th century accounts for low average height levels, it found.

A doubling of milk intake between 1875 and 1900 and initiatives taken in the 1920s to improve iodine intake are credited with boosting the height of Swiss conscripts, the study says.

The complex mix of factors now promoting "body breadth" while the growth in height has slowed down "have yet to be completely understood", it says.