Can a phone app really measure your body fat? From smart scales to a device that tracks metabolism, CAROLINE JONES weighs up the latest gadgets...

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Once, weighing yourself involved simply stepping onto a trusted pair of bathroom scales. 

Now it’s all gone high tech, with scales and other devices to use at home to measure body fat, your metabolic rate — even how much visceral fat you have.

This is a type of fat stored around the organs in the abdomen and is thought to be more dangerous than fat stored under the skin (subcutaneous fat), with high levels linked to an increased risk of heart disease and cancer.

Once, weighing yourself involved simply stepping onto a trusted pair of bathroom scales. Now it’s all gone high tech. Stock picture

To find out just how accurate these — often expensive — gadgets are we asked Clare Thornton-Wood, an NHS dietitian and obesity expert and spokesperson for the British Dietetic Association, to give her verdict. 

We then rated them.

BODY-FAT ANALYSERS

Denshine Portable Handheld Body Fat Mass Index BMI Analyzer Health Monitor, £12.99, amazon.co.uk

Denshine Portable Handheld Body Fat Mass Index BMI Analyzer Health Monitor, £12.99, amazon.co.uk

A handheld gadget that looks like a computer games console). Grab the handles and hold the monitor in front of you; it then measures your percentage of body fat, BMI (body mass index) — enter your height for this — and your basic metabolic rate.

EXPERT VERDICT: This uses a system called bioelectrical impedance which calculates your percentage of body fat by passing a painless electrical current through the body.

Fat causes greater electrical resistance, so slows the rate at which the current travels, while muscles, bone and blood have a high water content, so the electrical current travels through them easily and quickly.

Studies have shown bioelectrical impedance can effectively measure body fat levels, but readings are not always consistent as the water content of your body varies — even after a bath or shower.

Once it’s worked out your body fat percentage, the device calculates your resting metabolic rate (not walking or exercising etc).

Because muscle is active and needs more energy (calories) than fat does, the more muscle, the higher the metabolic rate and the more calories you will be burning off. This is a useful measurement to benchmark, as it should go up as you lose fat.

However, the bioelectrical impedance machines used in clinical studies will be much more powerful than this, which has fewer (just two) and smaller sensors and therefore is unlikely to be as accurate. 

4/10

Qardio base 2, £129.99, getqardio.com

Qardio base 2, £129.99, getqardio.com

A compact (34cm) step-on disc-shaped device (right) that weighs you and records the information to track your weight-loss progress.

It also calculates BMI and body composition — including muscle, body fat and water content — using bioelectrical impedance, displaying the results and automatically sending them to your phone, too.

It can work with the weight-loss app MyFitnessPal for extra weight-loss advice.

EXPERT VERDICT: Automatically storing progress on your phone can be very motivating when you’re dieting.

Some studies have shown that using similar apps regularly can lead to greater success. This has four sensors, less than the Omron (see right) which could mean it’s not quite as reliable but has more than the handheld Denshine reviewed above. This is easy to use but somewhat expensive. 

6/10

FitScanner Body Fat Calculator app, free from Google Play app store

FitScanner Body Fat Calculator app, free from Google Play app store

An app on your phone, this estimates your percentage of body fat from simply scanning an uploaded full-length photograph. The maker says the app does this by ‘machine-learning algorithms’.

EXPERT VERDICT: It’s hard to see how an image could give any meaningful data on body composition. Indeed, the admission by FitScanner that they can only give an ‘approximate body fat range’ and that accuracy is still a ‘work in progress’ says it all really. 

1/10

Seca New 203 Waist to Hip Ratio Ergonomic & Body Fat Measuring Tape, £7.79, uk.secashop.com

A retractable metal tape measure designed to establish the circumference of your waist and then your hips. It has a twistable dial which uses this data to show your waist-to-hip ratio (WHR) — a measurement that determines the amount of abdominal fat you have.

Seca New 203 Waist to Hip Ratio Ergonomic & Body Fat Measuring Tape, £7.79, uk.secashop.com

EXPERT VERDICT: Waist-to-hip ratio is now thought to be more reliable than BMI (body mass index) when it comes to understanding your risk of certain health problems.

The higher the ratio (essentially the larger your waist in relation to your hips) the more subcutaneous — and probably visceral fat — is stored around the abdomen which is linked to a greater risk of heart disease, stroke and type 2 diabetes.

Of course, you could just use a standard sewing-type tape measure, and then divide the waist measurement by the hip measurement — a healthy ratio is 0.9 or less for men, and 0.85 or less for women.

But this product’s curved case is easier to hold and the metal tape doesn’t stretch, making it accurate. A handy gadget that does the maths for you. 

8/10

HemeraPhit Personal Body Fat Tester Caliper, £7.45, amazon.co.uk

HemeraPhit Personal Body Fat Tester Caliper, £7.45, amazon.co.uk

Plastic calipers that measure your subcutaneous body fat ‘easily and accurately’ — you use the pincer-shaped tongs (right) to pinch a fold of skin around the tummy, waist, arms, buttocks or leg to get a measurement, then compare this to the body fat interpretation chart provided to work out your body fat percentage and what it means for your health.

EXPERT VERDICT: Calipers can measure the amount of fat under the skin (subcutaneous fat) and have been used for more than 50 years in hospitals and gyms and can be a useful way of monitoring changes in body fat over time.

However, the fat has to be pulled away from the muscle underneath so it can be hard to get an accurate measurement.

Plus, the location pinched needs to be exactly the same every time to compare measurements — so it can be better if someone else uses the calipers on you. The tongs are also a bit ‘plastic’ and flimsy compared to the metal ones used in a hospital. 

6/10

Omron BF511 Full Body Composition Monitor, £104.79, omron-healthcare.co.uk

Omron BF511 Full Body Composition Monitor, £104.79, omron-healthcare.co.uk

This looks like normal bathroom scales, but with a handle attached to a wire that pulls up from the centre (below). You hold the handle while the machine works out your body fat percentage and visceral fat. It can also give standard weight readings.

EXPERT VERDICT: Here we have another device that uses bioelectrical impedance to calculate the percentage of fat in your body. This one has more sensors — eight — than the other devices here, so the accuracy is likely to be better.

As well as subcutaneous fat, bioelectrical impedance is useful in measuring visceral fat. However, people with implanted devices such as pacemakers should avoid bioelectrical impedance devices as it can cause malfunction. 

8/10

WEIGHING SCALES

Accuweight Skidproof Bathroom Scale, £12.99, amazon.co.uk

Accuweight Skidproof Bathroom Scale, £12.99, amazon.co.uk

These display your weight as soon as you step onto them — they also have an anti-slip step, and your weight is displayed in large digits on a blue backlit screen (below), making it ‘easy to read even in dark conditions’.

EXPERT VERDICT: A good budget buy, but note that your weight will fluctuate during the day and day-to-day — depending, for example, on how hydrated you are and when you last ate — so weigh yourself only once a week.

Studies have shown people often weigh their heaviest on a Sunday night after a weekend of over- indulgence and less exercise, so a Friday morning is probably the best day for a weight check. 

7/10

Kern MPL 200K-1P Personal Floor Scales, £126, tester.co.uk

Kern MPL 200K-1P Personal Floor Scales, £126, tester.co.uk

WEIGHING scales with a waist-height pillar (right) that displays your weight readings in large digital figures, which the maker says are easy to read even in poor light. If you input your height, they also calculate your BMI.

EXPERT VERDICT: Easier for older people as they have a secure base, and measurements are shown in big digits closer to your eyes. However if your stomach is very large it could get in the way of the pillar.

These scales are also bulky, and will take up more space than standard scales.

BMI, measured by dividing a person’s weight in kilograms by their height in metres squared, on its own, isn’t always accurate — someone with a lot of muscles can appear to be overweight when they’re not. 

5/10 

Styku 3D body scanner, £10,500, styku.com

The makers claim it can perform a 3D body scan in 35 seconds. You stand on a slowly turning platform while a 3D camera takes images, using similar technology to an airport scanner (infrared imaging). It measures waist, chest and arms and uses the data to create a 3D model of your body, viewable on a phone or computer. This image gives a detailed analysis of the fat and muscle composition of your body.

EXPERT VERDICT: It gives an accurate body fat percentage and shows the location of body fat in pictorial form.

It’s hugely expensive, but if that is not a problem then it might be useful, but it’s probably best utilised with a trained professional to help you pick out the most useful bits of information.

While analysing body fat is a positive thing if you need to lose weight, for some people having such a detailed picture could exacerbate negative self-esteem issues.

Styku 3D body scanner, £10,500, styku.com