Why the scale lies, and what to measure instead

The scale answers a question you didn't ask

A scale measures mass. Water, food in transit, muscle, bone, fat, the jeans you forgot to take off. It has no idea which of those changed since yesterday, and neither do you when you're standing on it at 6am deciding whether to be pleased.

What you care about is composition: how much of you is muscle and how much is fat. Two people at the same weight can be a decade apart in how they move, and the scale scores them a tie.

Weight is a total. Composition is the point.

Why this matters more on a GLP-1

Ozempic, Wegovy, Mounjaro and Zepbound take weight off quickly. What they don't do is choose what kind. In the trial that got semaglutide approved for weight loss, the sub-group who had body scans lost roughly 40% of their total weight as lean tissue rather than fat.¹ Lean tissue is mostly muscle. So the scale says "great" while the part of you that climbs stairs is shrinking.

The fix is not complicated. A review of trials on people losing weight through calorie restriction found that adding resistance training preserved lean mass that dieting alone gave up.² Lift, eat enough protein, and the scale's number is made of the right stuff.

Muscle doesn't weigh more than fat

A kilo is a kilo. Muscle is denser than fat, so a kilo of it takes up less room. That is why people who start lifting often find their clothes fit before the scale moves, and why the scale is the wrong instrument for the first two months of a program. I used to say "muscle weighs more" in my old post. I was wrong on the physics and right on the point.

What to measure instead

Goal pants. Find a pair of pants you can't quite button and hang them where you'll see them. Every couple of weeks, same time of day, try them on. First the button reaches. Then it closes. Then you can sit down in them. Then you need a belt. No number, no 6am verdict, and a far better read on your waistline than a scale can give, because pants don't care what you ate last night.

Alongside the pants: two or three lifts, and whether the numbers are going up. A photo in the same doorway in the same light, monthly. And the honest one: whether the stairs, the ski run or the grandchild are getting easier. If those are moving and the scale isn't, the scale is the one that's wrong. A DEXA scan once a year if you like data.

Where I fit in

I'm a personal trainer with a rehab specialist's training and a Certificate IV in Nutrition Coaching, and both come with every session. If you're on a GLP-1 and worried about what's coming off, here's the page for that. If you're over 40 and want the muscle back, here's that one. If the plateau is the problem, read this next.

So there you have it. Keep the scale if you like it. Just stop letting it grade you.

1. Wilding JPH et al., "Once-Weekly Semaglutide in Adults with Overweight or Obesity," New England Journal of Medicine, 2021 (STEP 1), DEXA sub-study.

2. Sardeli AV et al., "Resistance Training Prevents Muscle Loss Induced by Caloric Restriction in Obese Elderly Individuals: A Systematic Review and Meta-Analysis," Nutrients, 2018.