It’s known that obese children tend to have “flatter” feet than their normal-weight peers, but it has been unclear whether that reflects a potential problem in the foot’s bone structure or simply extra fat padding. A new study suggests that it’s both.

In general, people with “flat feet” have a lowered arch at the inside of the foot, such that if they wet their feet and stood on a flat surface, they would leave a complete footprint.

All babies and toddlers have flat feet, with the arch developing during childhood; obese children are more likely than their thinner peers to retain a flat foot - as measured by footprint in studies - and it has been assumed that this is because their extra weight creates a “fallen” arch.

But the other possibility is that heavier children simply have more fat padding the soles of their feet.

This is important because flat feet caused by lowered arches, while not problematic for most people, can cause symptoms for some. Some children and adults have foot pain, and in the long-term, flat feet can contribute to ankle or back pain, for instance.

So for the new study, published in the International Journal of Obesity, Australian researchers used ultrasound tests to examine the feet of 75 obese children and 75 thinner children between the ages of 6 and 10.

They found that, in general, obese children did in fact have more fat padding the soles of their feet. But they also tended to have lower arches.

Exactly what, if anything, that might mean for obese children’s foot function or risk of future musculoskeletal problems is unclear, according to the researchers, led by Dr. Diane L. Riddiford-Harland of the University of Wollongong.

They say more research is needed to follow children over time, to see how obesity - as well as weight loss - might affect the structure and health of their feet in the long run.

When it comes to flat-footedness in children in general, recent studies have painted a positive outlook. A study published last year in Pediatrics, for example, found that among 11- to 15-year-olds, there was no relationship between the height of their arches and their performance on motor-skill tests - which included jumping, balance and speed.

In general, flat feet that cause no pain need no special therapy. If a child does have a pain, a doctor may recommend arch supports for the shoes or physical therapy.

SOURCE:  International Journal of Obesity, online June 22, 2010.