You may know the drill: After months of hard work in a new exercise routine, you still weigh exactly the same. Many coaches and trainers chalk it up to changing body composition. For instance, after dedicated hours of core work, your trunk may be swapping out fat for denser muscle, so your overall weight stays the same.
But how do you tell if you’re really gaining muscle, or if your trainer is just being kind? The best way is to use a scale with a built-in body-fat analyzer. These devices are often criticized for not giving an accurate reading the first time. They use a weak electrical current to test your body’s composition, and calculate results using a formula for your age, sex, and other factors. If you’re especially athletic, the numbers may not even be close. But body fat scales do nail the trends. They are valuable tools to see if you are getting leaner over the weeks, and to motivate you as you go from a vague resolution at New Year’s to Tough Mudder shape for the spring.
The following monitors have great features and deliver the most accurate results in the category. Keep in mind that for these devices, accuracy is also dependent on you. To get good, consistent readings, you need to hop on the scale at the same time of day, at roughly the same hydration level, in the same temperature room, and without having exercised in the last few hours.
The Best Body Fat Scales: Withings Smart Body Analyzer
The best body fat readings are done in consistent circumstances: same time of day, same level of hydration. So it’s natural to track resting heart rate, which needs the same restrictions, while you’re at it. Withings Smart Body Analyzer, coming out next month for $150, takes your pulse through your feet when you step on it. It sends that data, along with the estimated body fat percentage of your legs, to an app on your iOS or Android phone. Withings connects via Wi-Fi, Bluetooth, or the new low-power standard, Bluetooth Smart.
We like how Withings has an athlete mode for those getting more than eight hours of exercise per week. Presumably, the device uses a different statistical formula to derive body fat, because other scales with this feature deliver more tailored results.
The Best Body Fat Scales: Tanita BC-1500 Ironman Radio Wireless
The most important feature of the $625 BC-1500 is that it does segmented body fat analysis, meaning it analyzes the fat on your trunk, legs, and arms (most monitors attempt to measure the fat on your legs). The downside, of course, is that the procedure for the full-body scan involves standing on the scale while gripping the handles on the sides, an undignified and somewhat awkward position to be in. Data is then automatically sent to your computer using an ANT+ wireless adapter for long-term tracking. And because most Garmin devices use ANT+, it pairs well with your Forerunner.
The Best Body Fat Scales: Fitbit Aria
Every time you step on the $130 Aria, it shuttles data off to your Fitbit account online. We especially like being able to view the Fitbit.com graphs in the Web browser to identify long-term trends (such our annual backslide between Thanksgiving and New Year's). The Aria shares information with the site using your home’s Wi-Fi network, comes in white or black, and recognizes eight different people (important, since the formulas for calculating fat vary according to age and sex).