Why Bathroom Scales Lie | Body Composition Guide
The £10 Gadget Versus a £5,000 Lab
Bathroom scales cost a tenner. Our InBody 270 analyser costs about the same as a second‑hand Mini—because it tells a very different story. After running hundreds of scans on Uxbridge residents since 2023, one thing is crystal clear: body‑weight alone explains very little about real health or aesthetic progress.
Why Scale Weight Fluctuates Daily
The number you see at 7 a.m. can swing 1–2 kg in 24 hours—even if you spend the whole day on the sofa. Sodium intake, hydration status and glycogen replenishment all shift water balance markedly. Women can also gain 0.5–1 kg around ovulation and menstruation due to hormonal water retention.
Add to that the weight of undigested food (yes, last night’s burrito is in that reading), clothing, bowel contents and even bone‑density changes over time, and you can see why two weigh‑ins 48 hours apart can feel like different people.
Muscle Is Denser Than Fat—Here’s Why That Matters
A kilo of feathers weighs the same as a kilo of lead, but it takes up vastly more space. Same with body tissue. When you strength‑train and eat enough protein, you can look slimmer while the scale stays the same—or even rises. That’s exactly what happened to Sat in last weeks check in: +3.4 kg muscle, −4.5 % body fat.
Factors That Inflate (or Deflate) the Number
Water retention after salty meals, alcohol or a tough leg session.
Glycogen storage: every gram of stored carbohydrate drags ~3 g of water with it.
Hormones: cortisol spikes from stress, oestrogen in the luteal phase, and insulin after a carb‑heavy evening.
Digestive contents: up to 1 kg depending on fibre intake and gut transit time.
Timing & clothing: weigh at 6 p.m. wearing jeans and you’ll add 0.4–0.8 kg straight away.
None of these say anything about whether you’ve added muscle or lost fat.
Why We Track Body Composition Instead
Our InBody machine uses multi‑frequency bio‑electrical impedance to segment muscle and fat across each limb and the trunk. That means we can see exactly where change is happening, not just an overall figure.
How to Measure What Matters
Schedule a baseline InBody scan. No guess‑work; just data.
Re‑scan every 4–6 weeks, same time of day, fasted, post‑loo stop.
Pair numbers with progress photos, strength logs and how clothes fit.
Adjust nutrition, not just calories—focus on consuming adequate protein and fibre. (chat with a healthcare professional if you are unsure)
Pro‑tip: Delete “weigh‑in Wednesday” from your calendar and book “scan day” instead.
Ready to Ditch Scale Anxiety?
We’re opening five new spots in our Nutrition & Body‑Comp Programme this month. Book your complimentary InBody assessment and we’ll build a data‑driven plan for you.
👉 Claim your free scan here — or pop into the studio and say hi.
Coach Tony & Team Riverside
Disclaimer
Information provided is for educational purposes only and is not a substitute for medical advice.
