March 1, 2016, by Emma Rayner

Weighing things up with The One Show

Physiology experts in the Division of Medical Sciences and Graduate Medicine have been helping BBC TV’s The One Show solve a domestic mystery – how accurate are our bathroom scales?

Dr Beth Phillips agreed to help the popular primetime show investigate five different, newly bought domestic bathroom scales, along with three keen and sporty students from the University’s Muscle and Athletic Sports Society. The report airs tonight on BBC 1 at 7 o’clock.

Presenter Dominic Littlewood came to Beth’s lab at the Royal Derby Hospital to film the report. He said: “There’s a lot of emphasis nowadays on health, diet and fitness with a lot of people in the UK trying to drop a few kilos and tone up. So we at The One Show wanted to test five sets of high-street bought bathroom scales for accuracy against the University’s properly calibrated scales to see how the weight readings compared. The results were interesting!”

The weighing and scans were supervised by our physiology expert Dr Beth Phillips who was also interested to know whether domestic scales are as reliable as the manufacturers claim. Beth said: “To be as accurate as we could, we carried out DXA scans on our three student volunteers to measure their percentage body fat and also weighed them on our well-calibrated scales. A DXA scan is a very low-dose X-ray scan of the whole body that is clinically used to examine bone mineral density in patients. The DXA can also measure total body composition including body fat to a high degree of accuracy.

“When we compared our results with the weight and percentage body fat measurements on The One Show’s three domestic scales, of varying makes and prices, we found a variety of discrepancies. None of the scales showed a correlation with the DXA results and the variation between the scales was very large with one volunteer have a body fat percentage of 13% on one set of scales and 26% on another with a DXA-derived figure of 17%. Nonetheless the repeatability of the scales was good when our volunteers repeated their measures on the scales. These results suggest that although the numerical value obtained by these scales may not be very accurate, and is known to be influenced by factors like hydration status and food intake, they likely do have use for tracking changes in individuals over time.”

One of the volunteers, 2nd year Neuroscience student Sarah Barron, said: “I was surprised to see just how variable the results were between each set of domestic scales, and even that the most expensive scale, at £140, did not correlate significantly with the body fat percentage readings from the DEXA scanner! It shows that if you want to track your fluctuations in weight and body fat percentage, you’re just as well off buying the cheapest one of the range! It was reassuring to know that after the DEXA results were revealed that myself and my team mates were all in the healthy range for body fat percentage, BMI and that we all had an above average bone density – probably from all the weight training!”

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