Why the Scale Was Lying to Me for a Year: My InBody Scan Story

Disclosure: This post contains affiliate links. As an Amazon Associate, I earn from qualifying purchases at no extra cost to you.

For a long time, the only tool that told me anything about my body was a regular bathroom scale. I’d step on it, see a number, and either feel good or feel bad about it. No context, no breakdown, no answer to the question of whether those kilograms were muscle, fat, or water. In my old gym, which cost 20 euros a month, nothing more advanced was on offer. It wasn’t until I moved to a new, premium club and booked a session with a personal trainer that I stood on an InBody 770 for the first time. That moment changed how I look at my own progress.

A Number on a Scale Told Me Almost Nothing

Before InBody entered my life, I had one goal: build muscle mass. I wanted to look better, get bigger, feel stronger. The scale kept creeping up and I treated that as success. But did I actually know what was growing? No. It could have been anything: muscle, fat, water retention. A regular scale doesn’t distinguish between these. It shows you a sum, and a sum on its own is nearly useless for anyone training seriously with weights.

There was another problem that only surfaced once I got my first scan: a clear asymmetry between my left and right arm in terms of muscle mass. I’d been training with a barbell, and without realizing it, one arm was compensating for the other. Without the scan, I would have kept training with that imbalance and never known about it. It was the segmental breakdown on the InBody printout that pushed me to lean more on machines with independent loading for each arm. That’s a concrete, actionable signal that no bathroom scale could ever have given me. I’d already touched on how inconsistent training habits held me back in how I finally stopped quitting the gym, and this asymmetry turned out to be another piece of that same puzzle.

First Scan: A 12-Year-Old’s Metabolism and 80 Out of 100

My first session with the InBody 770 came bundled with a two-hour session with a personal trainer. That was September 2024. The device measured everything: muscle mass, fat levels, body water, a segmental breakdown for each limb, and a metabolic age estimate.

That last number stuck with me. Metabolic age: 12 years old. I was 25 at the time, and metabolically my body was functioning like a child’s. My muscle mass came out to 40.3 kg, fat mass was just 5.9 kg, or 7.8% of total body weight. Total body weight: 76.3 kg. The InBody fitness score: 80 out of 100. A solid result, but I knew there was room to improve.

Two Months, One Concrete Change, and a Scan That Told the Truth

Between September and November 2024, I made exactly one deliberate change: I started actually counting protein. Not a training overhaul, not a new program. Just protein. I began with low-fat cottage cheese (twaróg), which I ate for a month or so to build the habit, then switched to skyr, which I already covered in my post about tracking protein to gain 10kg. My training itself didn’t change, same push-pull split, same frequency. The one variable that shifted was that I finally knew how much protein I was actually giving my body each day.

In November 2024, I did my second scan. Weight: 79.1 kg, almost 3 kg more than in September. If I’d only had a bathroom scale, I might have shrugged it off, or worse, started worrying I was gaining too fast. But the scan told a completely different story. Muscle mass went from 40.3 to 42.3 kg, two kilograms of actual muscle in two months. At the same time, fat mass dropped from 5.9 to 5.4 kg, half a kilogram less. Fitness score: 86 out of 100, six points higher than before.

A regular scale would have told me: you gained almost 3 kg. End of information. The InBody told me: you gained 2 kg of muscle and lost half a kilogram of fat. That’s the difference between a data point and noise.

Body Composition vs. Body Weight: Why They’re Not the Same Thing

This is exactly where most people training seriously misread their own progress. Body weight is a sum of several different components, and each one behaves differently in response to training and diet. Muscle is denser than fat. Someone who’s gaining muscle and losing fat at the same time can weigh exactly the same as a month before, or even more, while looking completely different and being stronger and healthier. A regular scale will never tell you that story.

Hydration level, time of day, your last meal, all of it shifts the number you see. You can weigh a kilogram less in the morning than in the evening. That’s not data, that’s noise.

A 2019 study comparing the InBody 770 against DEXA, the more rigorous lab-based reference method, in exercise-trained men and women undergoing a four-week calorie-restricted diet found something reassuring. Although the InBody overestimated fat-free mass and underestimated fat mass compared to DXA in absolute terms, the changes in fat mass, fat-free mass, and body fat percentage that the InBody picked up over the four weeks were statistically no different from what DEXA measured. In other words, the device tracks the direction and size of your progress reliably, even if its absolute numbers don’t perfectly match a DEXA scan (Antonio et al., 2019, Journal of Functional Morphology and Kinesiology, 4(2), 23, DOI: 10.3390/jfmk4020023). https://www.mdpi.com/2411-5142/4/2/23

A Health Check at Work and What Came Out of It

A few months later, in February 2025, I went through a comprehensive health check organized by my employer. As part of it, I had another body composition scan done, this time on a different device. Different brand, different underlying calculation method, so I’m not comparing those numbers directly to my InBody 770 results. Different BIA devices use their own proprietary algorithms and can produce noticeably different readings even on the same day, which is worth keeping in mind whenever you’re interpreting any single scan. The muscle mass figure from this work scan, for instance, looked higher than what the InBody had shown me, which only reinforces that you shouldn’t treat results from different machines as directly comparable, let alone as absolute truth.

Still, a few things stood out. Metabolic age: 12 years again. Visceral fat at level 1, the lowest possible reading. Body weight had climbed to 81.6 kg. Whatever I was doing, it was working. That wasn’t a random number, it was the result of two years of consistent training and a growing awareness of what I was actually eating, something I touched on from a different angle in the post about the beach photo that started all of this.

Is a Home Body Composition Scale Worth Buying?

Short answer: it depends what you’re expecting from it. Once I’d seen what those first two scans could tell me, I naturally started looking at the cheap smart scales on Amazon, the ones in the 30-50 euro range. The more I read, though, the more skeptical I got. The gap between an InBody 770 and a typical home scale is fundamental. The InBody 770 uses eight contact electrodes, measures each limb and your trunk separately, and runs multiple electrical frequencies at once. A cheap bathroom scale sends a single signal through your feet and estimates the rest with generic formulas. It’s a bit like comparing a full blood panel to checking your pulse.

A separate study on 155 exercise-trained men and women, comparing the Bod Pod, InBody 770, and DEXA, found that even the InBody 770, a piece of equipment that costs thousands of euros, systematically overestimated fat-free mass and underestimated body fat percentage relative to DEXA. If a machine in that price range still has real limitations, the limitations on a 40-euro bathroom scale are bigger still.

That doesn’t mean home scales are pointless. Used consistently, always at the same time, in the morning, fasted, they can help you track a trend over time. But as a single-day snapshot, especially compared against another person or another device, they’re unreliable. That’s why I’ve decided to keep relying on the InBody at my gym rather than investing in a home alternative that wouldn’t give me the same quality of data.

Yazio, Macros, and the Next Level

Right now I’ve taken this a step further. I installed Yazio and I’m logging everything I eat: carbs, fat, protein, total calories. It’s no longer just “eat a lot of protein.” It’s a deliberate, day-by-day account of what’s actually going into my body. The next InBody scan will tell me whether that translates into results.

But you need a reference point for any of this to mean anything. You can’t track changes in body composition without actually measuring body composition. A bathroom scale won’t do that for you, not with any real precision. If you have access to an InBody at your gym, even two scans a year will give you more useful information than weighing yourself every day for twelve months on a regular scale.

Disclaimer: This post reflects my personal experience only and is not medical or nutritional advice. Please consult a doctor or qualified professional before making changes to your diet or training routine.