They measured height, weight and body mass index - calculated by dividing weight in kilograms by the square of your height in metres.

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All models were required to have a body mass index -- a ratio of height and weight -- above 18, the minimum limit considered healthy by the World Health Organization.

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According to the first ever nationwide sizing survey using 3D body scanners, both typical waist-lines and height have increased over the last 30 years.

BBC: Children 'have wider waists now than in 1978'

The study also took into account body mass index (BMI) - a measure which relates weight to height.

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The survey, called Shape GB and carried out by Select Research, suggests that two current beliefs prevalent among retailers are wrong: that boys' and girls' body shapes do not differ significantly before the age of seven, and that the average height of five-year-old boys is 110cm when it is actually 115cm.

BBC: Children 'have wider waists now than in 1978'