How to choose a body composition scale in New Zealand
A body composition scale tells you what your weight is made of, not just how much there is. This guide explains what these scales measure, what to check before you buy one in New Zealand, and how to get readings you can trust.
Short answer. A body composition scale estimates fat, muscle and water from a tiny electrical current. Choose one with hand grips (8 electrodes) if you want arm, leg and trunk readings, check the app's price and data policy, and weigh in under the same conditions each morning. Use the trend, not a single reading.
What a body composition scale measures
Most home scales use bioelectrical impedance analysis (BIA). The scale sends a tiny, harmless current through your body and measures how hard it is for the current to pass. Water-rich tissue such as muscle lets current through easily. Fat resists it. Software then turns the resistance, your height, age and sex into estimates of body fat, muscle, body water and more.
The key word is estimates. A home scale does not see inside your body. A DEXA scan or a clinic machine is more precise, but a good home scale is very useful for something else: showing your trend week after week, in the same conditions.
What to look for before you buy
1. Electrodes: feet only, or hands and feet
Basic body-fat scales have four electrodes under your feet, so the current only travels through your legs and lower body. Scales with hand grips add four more electrodes, so current also passes through your arms and trunk. Our 4 vs 8 electrode guide explains the difference.
2. Frequencies
Lower frequencies mostly travel around cells and mainly reflect body water outside them. Higher frequencies pass through cell membranes. Scales that use more than one frequency have more information to work with than single-frequency scales.
3. Segment readings
Some scales give one whole-body number. Segmental scales report each arm, each leg and the trunk separately. That helps you spot imbalances, such as one leg carrying less muscle after an injury, and see where changes are happening.
4. Honest accuracy claims
Be wary of "99% accurate". Ask how the maker tested the scale and whether comparison data against DEXA or a clinic machine is available. Remember that hydration, food, exercise and room temperature all move BIA readings. Our guide on body fat scales versus DEXA shows what studies found.
5. The app, the price and your data
Check whether the app is free or needs a subscription, whether you can export your data, whether several family members can have their own profiles, and where your readings are stored. Some apps keep your body data on company servers. Others keep it on your phone.
6. Safety
BIA scales are not suitable for people with a pacemaker or another implanted electronic medical device, and body composition is not measured during pregnancy. Read the manual and check with your doctor if you are unsure. See our safety guide.
7. Support in New Zealand
Goods sold in New Zealand by a business must be of acceptable quality under the Consumer Guarantees Act. Look for a seller with a New Zealand address, a clear warranty and a returns policy, so a faulty scale is easy to sort out.
The main types of scale compared
| Type | What you get | Limits |
|---|---|---|
| Weight-only scale | Weight | Cannot tell fat from muscle |
| Foot-to-foot BIA (4 electrodes) | Whole-body fat, muscle and water estimates | Current passes through the legs only, so arms and trunk are inferred |
| Hand-and-foot BIA (8 electrodes) | The above plus separate arm, leg and trunk readings | Still an estimate; you must hold the grips correctly |
| Clinic machine or DEXA | The most detailed picture | Costs money and an appointment each time |
How to get readings you can trust
- Weigh in at the same time each morning, after the toilet and before eating or drinking.
- Stand barefoot on clean, dry feet, and hold the grips with straight arms if your scale has them.
- Avoid weighing straight after hard exercise, a sauna or a long soak.
- Judge by the weekly trend, not a single day. Water alone can move readings: in a 2022 study, adults who drank water had the extra body mass recorded as extra fat mass (see how accurate body fat scales are).
Where the Everhale scale fits
Everhale is designed in Auckland. The scale has 8 electrodes (four in the glass platform and four in a hand bar), two measuring frequencies (20 kHz and 100 kHz), and reports fat and muscle for each arm, each leg and the trunk. A 3.5-inch colour screen shows each family member's name. The free app turns your goal into a daily plan, with no subscription, and keeps your readings on your phone. Founding-member price is NZ$279 including GST, with free New Zealand shipping, a 2-year warranty and 7-day returns. We are pre-launch, so join the waitlist to hear the launch date first.
Common questions
Are body fat scales accurate?
Home scales estimate body fat from electrical resistance. They can differ from a DEXA scan, sometimes by several percentage points, depending on the model and the person. They are best used to follow your own trend over weeks, in the same conditions each time.
What time of day is best to weigh in?
First thing in the morning, after the toilet and before eating or drinking. The point is to repeat the same conditions, so changes you see are real changes.
Can I use a body composition scale with a pacemaker?
No. Body composition scales pass a small current through the body and are not suitable for people with a pacemaker or another implanted electronic medical device. Check with your doctor.
Do I need a subscription for the app?
It depends on the brand. Check before you buy. The Everhale app is free with the scale, with no subscription.
Sources
- Czartoryski et al. (2020), Body Composition Assessment: A Comparison of the DXA, InBody 270, and Omron, Journal of Exercise and Nutrition
- Tinsley et al. (2022), Influence of acute water ingestion and prolonged standing on raw bioimpedance and subsequent body fluid and composition estimates, Journal of Electrical Bioimpedance
- TCTMD (2023), 'Smart' devices with bioimpedance tech may interfere with cardiac implants (reporting a Heart Rhythm study from the University of Utah)
- Consumer Protection (NZ), Consumer Guarantees Act
Keep reading
- 8-electrode vs 4-electrode body fat scales
- Body fat, muscle, visceral fat and BMR explained
- How accurate are body fat scales vs DEXA?
- Are body composition scales safe? Pacemakers and pregnancy
Everhale is a wellness product, not a medical device. This guide is general information, not medical advice. Talk to your doctor or a dietitian about your own health.