What Factors Can Affect My InBody Scan Results?

InBody scanners measure body composition using bioelectrical impedance — which means they send a small current through your body to estimate fat, muscle, and water content.

That also means anything that affects your body’s water balance can throw off your results. As one fitness forum user put it: “InBody scans are affected by numerous factors: what you ate, drank, your hormonal cycle, [and] what workout you recently completed.”

Let’s break down the biggest influencers.

1. Hydration Is the #1 Factor

Your hydration status can cause swings of 2–5% in body fat readings.

When you’re well-hydrated, muscles appear fuller and leaner. Dehydration, on the other hand, can make you look softer and increase your estimated body fat.

Even drinking a lot of water right before your scan can skew results — the machine might overestimate your muscle mass and underestimate fat.

2. Food Intake Can Skew the Numbers

Eating before a scan adds temporary weight — literally, the food in your stomach — and may shift water balance as digestion kicks in.

Many users report that even a light meal before scanning can “mess up the scan majorly.” For best results, scan on an empty stomach, ideally after using the bathroom.

3. Exercise Affects Blood Flow and Water Retention

Working out before a scan, especially lifting or cardio, pumps blood into your muscles and shifts water around your body.

This can cause muscles to appear more swollen or artificially lean. For accurate, consistent readings, it’s best to scan before exercising, not after.

4. Time of Day Matters More Than You Think

Your weight and body water fluctuate throughout the day.

In the morning, you’re typically more dehydrated (after hours of sleep) and have an empty stomach. By evening, you’ve eaten, drank fluids, and possibly exercised — all of which can impact your scan.

Many people choose to scan first thing in the morning for this reason.

5. Alcohol and Sodium Can Wreck Your Numbers

A salty meal or a night of drinking can result in bloating or dehydration the next day.

Both affect how your body holds water, which in turn throws off the InBody’s readings. Users often report strange results after drinking alcohol or eating high-sodium foods.

6. Menstrual Cycle Affects Results for Women

Hormonal changes during PMS or menstruation can lead to temporary water retention, inflating your body fat % reading.

This isn’t actual fat gain — it’s water weight. Many women report more accurate results when they scan outside their menstrual window.

7. Not All Machines Are Created Equal

Even two InBody machines of the same model can have slightly different calibrations.

If you want consistent results, stick to the same machine every time. Switching between devices could introduce minor errors that muddy your progress tracking.

How to Get the Most Accurate Scan

The key to consistency is standardization.

Try to scan:

At the same time of day (e.g., Monday mornings)
Before eating or drinking
After using the bathroom
Before exercising
On the same machine
Wearing similar clothing (or none, if allowed)

Also, be hydrated — but not excessively. Skip metal accessories and follow any posted prep guidelines.

Most importantly, remember: individual readings can be off, but if you follow the same process and track trends over time, you’ll get a reliable sense of whether your body fat is going up, down, or holding steady.