The best smart scales 2019

Everyone’s getting fitness trackers, walking more than 10,000 steps a day, donning the trainers and setting out on a jog recommended by RunKeeper or another of the many exercise apps - especially after a weighty Christmas and with New Year's resolutions to keep.

For many of us exercise is as much about weight loss as it is general fitness. All those Fitbit steps go hand in hand with the 5:2 Diet or some other fashionable eating regime because we realise we’re overweight and need to shed a few kilos. You need to look for scales that will help you maintain a healthy weight and look at other health metrics.

A standard set of digital scales will do the trick, but in today’s world of the quantifiable self we appreciate all our data to be digitally collated and presented to us in attractive graphs and charts.

For this, we need a set of smart scales that sync with a smartphone app.

Not just weighing machines

Smart scales measure a lot more than our weight. A decent set should also inform us of our Body Mass Index (BMI), lean mass, and body fat percentage. These metrics help us understand what our own best weight should be, as it depends on your height as much as your actual weight in kilos or stones.

When measuring the various health stats remember that these averages are just that, and an individual’s best ranges may differ depending on various factors. If in doubt discuss these with your doctor.

Common health metrics for smart scales include:

BMI - this is a measure that shows if you are a healthy weight for your height. 14 stone (89kg) might be an unhealthy weight for someone of average height, but perfectly acceptable for a 6ft 5in man. Doctors suggest that an ideal BMI for adults is in the range 18.5 to 24.9.

Body fat percentage - this is the portion of your body made up of fat cells. For men aged 20 to 40, 10-20 percent body fat is considered healthy. For older men the range 18-25 percent is good. For women aged 20 to 40, 19-26 percent body fat is healthy. For older women 23-35 percent is healthy.

Lean mass - a measure of muscle, organs, bones and water, rather than essential or storage fat. Having a high percentage of lean mass boosts your metabolism, making it easier to maintain an overall healthy weight.

Visceral fat - this is fat that exists around your vital organs, and is one of the main risks to long-term health.

Body Water Percentage - the rate of water in body composition. Aim for a body water percentage just over 50 percent. It depends on age as well but men should try to get to a total body water percentage between 50 and 65 percent. The ideal range for women is between 45 and 60 percent.

Bone Mass - bone density is an important health metric because, like muscle, bone is a living tissue that can become stronger with exercise, as well as a healthy diet (calcium and vitamin D). For most people bone mass starts to reduce after the age of 40, and regular exercise can prevent this loss.

Basal Metabolic Rate (BMR) - an estimation of the energy (measured in calories) expended by the body at rest to maintain normal body functions (heart beating, respiration, maintenance of body temperature, etc).

Pulse Wave Velocity (PWV) - currently exclusive to the Withings Body Cardio (though disabled in the US thanks to regulatory issues) this is a measure of arterial stiffness and blood flow rate that is used clinically as a key indicator of heart health and blood pressure problems.

Sync - Fitbit users might prefer the automatic syncing between the company's scales and the app, and Withings tracker users will choose the Withings scales. But you can use any of these scales, and always manually log your weight into your particular health app. And most sync well with Apple Health or Google Fit.

Some scales claim they sync with Fitbit, but it's usually a round-about process. For example, Withings scale users are able to share the data from their Health Mate app account to their Fitbit app. So, data can be shared from the Withings app to the Fitbit app, rather than from a Withings scale directly to the Fitbit app.

Fitbit users might not get many metrics from the Aria 2 and Aria Air (see reviews below) but the sync is automatic.