Smart scales and body tape measures: how to choose

How to choose a body-composition scale

These scales send a very weak electrical current through your body and estimate fat, water and muscle mass from the resistance it meets. It is an equation-based estimate, not a direct measurement, which is why two models can give different numbers for the same person on the same day.

Before comparing models, decide what you want the data for. If you just want to follow your weight and body-fat trend week to week, a simple foot-electrode bioimpedance scale is enough. If you want more detail, some models add hand grips so the current travels through the arms and torso as well.

• Electrodes: feet-only is the common and cheaper design; hand grips make the reading more complete.
• User profiles: essential if several people share the scale.
• App and data export: handy for charts, but do not make it your main criterion.
• Hydration sensitivity: every model suffers from it, so how you use the scale matters more than the brand.

What actually matters (and what doesn't)

Consistency is what counts. Weigh yourself at the same time, in the same conditions and with the same hydration, for example in the morning after using the bathroom and before eating or training. Look at the average of several weeks, not a single day: your weight can swing a kilo or two from water and food without any change in fat.

The decimal point matters less. A body-fat reading of 18.4% is not more reliable than 18%. Do not trust metrics such as metabolic age or body score either; they are manufacturer-specific calculations that are of little use for decisions. And an absolute body-fat figure from a home scale cannot be compared with a DEXA scan: use it to see changes, not to label yourself.

The body tape measure: the cheap tool most people skip

A retractable body tape measure costs very little and measures something a scale cannot see: where your body is changing. Waist, hips, arm and thigh, measured monthly at the same spot, show whether you are losing fat or gaining muscle even when your weight stays put. It is also what you need for the Navy method of estimating body fat.

Measure without pulling tight, keep the tape parallel to the floor, and read after a normal exhale. If you can, note the exact landmark (for instance, level with the navel) so you can repeat it the same way.

Which option fits you

If you are starting out and want a trend reference without spending much, the budget bioimpedance scales on the list (best value) do the job. If you want a fuller reading, the recommended mid-range model with hand and foot electrodes and several profiles suits families and anyone who tracks regularly. Whichever you pick, the tape measure is the inexpensive companion worth owning.

A caution: bioimpedance scales are generally not recommended for people with pacemakers or other implanted electrical devices, or during pregnancy. If that applies to you, check with your doctor first.