MOST of us dread stepping foot on the bathroom scales.
One day they might tell you that you're a certain weight - and the next they're making out that you've gained 5lbs.
It's not just your scales that are the problem - lots of them could be wildly inaccurate.
Professor Will Stewart, a spokesman for the Institute of Engineering and Technology, told The Sun that where you stand and general wear and tear can be responsible for reading errors.
"They might not be so accurate in the first place if they're not well made," he said.
Electronic scales, he said, are better than mechanical ones simply because there "is less mechanism to go wrong".
Richard Black, managing director of Marsden, told The Sun that domestic scales may well be inaccurate because they often use low-cost parts and are not subject to rigorous testing procedures.
"Gravity is different depending on where you are in the world (the nearer you are to the equator, the less gravity there is), so if you use a weighing scale in the UK that's been made in another country, it may not be calibrated correctly.
"Domestic scales tend to be mass produced and will not undergo the stringent testing and calibration procedures that professional medical scales, like those used by GPs, will be subject to.
"Additionally, if a scale is used on an unsuitable surface like a deep-pile carpet, it’s likely to give you an inaccurate reading."
He also explained that scales, like everything, have a shelf-life.
Over a long period of time, weighing scales are bound to lose their accuracy and need to be recalibrated.
The issue is that many domestic bathroom scales require parts that are rarely available - so they end up getting binned rather than repaired.
When the scale moves up or down, it only tells you how much you have lost or gained, not what you have lost or gained
Richard said that electronic scales were more reliable than the mechanical versions because there are fewer working parts "which means there is less to go wrong".
"The weight can be read wrong with a mechanical scale, depending on where you stand on it and the angle from which you’re viewing the dial," he said.
"This could mean the reading could be read incorrectly by as much as 1kg or more.
"With an electronic scale, the reading is clear cut.
But Professor Stewart said that it isn't wholly fair to blame scales for readings entirely.
When we asked him if temperature and surface material really affected the numbers, he told us that "these errors are VERY small - you can't blame them if your weight looks high!"
"Many ‘inaccuracies’ are not to do with the scales - our weight varies anyway according to what we have drunk/eaten, time of day etc (and how many clothes we might have on!)," he pointed out.
And if you're using the same scale every week, it doesn't really matter if they're a little bit out - you're still getting an update on your progress.
SO, should you really bother weighing yourself at all?
Jonathon Taylor a senior personal trainer at Ultimate Performance, told The Sun that while weight changes are good to keep an eye on, you need to interpret them carefully.
"When the scale moves up or down, it only tells you how much you have lost or gained, not what you have lost or gained," he said.
"Your bodyweight can fluctuate daily due to several factors that are completely unrelated to how much body fat or muscle mass you have.
"For example, how much you sweat, your food and drink choices, the time you weigh in and when you last ate can all cause your weight to fluctuate from day to day.
"Weight loss is not a smooth process, and several weird things can happen to your weight when dieting, such as sudden weight gain, weight loss or even stalls.
"To counter this, we ask our clients at Ultimate Performance to weigh themselves every day but to focus on the weekly average (which helps smooth out any fluctuations).
"We also don't rely on a single assessment tool. Instead, we also take progress pictures and circumference measurements, measure body fat percentage and monitor gym performance."
For the most accurate bodyweight readings he recommended weighing yourself first thing in the morning, at roughly the same time, before you eat or drink anything and after you've used the bathroom.
Just how much should we be forking out on our scales?
Jonathon said: "There is very little research to support the accuracy of high-tech (and expensive) scales that attempt to measure your body fat.
"So, you're not missing out by only purchasing a standard digital bodyweight scale."
When it comes to basic weight readings, however, Richard told us that price can make a difference.
"The most reliably accurate scales you can buy are those that are ‘approved’ – in the case of personal scales, these would be Class III Approved Patient Weighing scales.
"This means they are legal for medical use, however, these scales do command a higher price.
"This is because every Class III Approved scale uses higher quality parts and will undergo thousands of accuracy tests, including temperature tests, and consistency in readings, which is called repeatability.TUMMY TROUBLES 'BACK TO HEALTH' WEIGH TO GO Tasty treats
"Each scale is individually tested and is verified as being accurate for use; it is accompanied by a legal document, a Declaration of Conformity."
Bathroom scales don't undergo that form of legal examination and aren't bound by regulations.
Richard said he believed that bathroom scales may well be affected by things like changes in temperature.
"For these reasons bathroom scales often lack accuracy and are not fit for use in hospitals or GP surgeries where Class III scales are used to weigh patients to enable the accurate and reliable prescription of medication."
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