The bathroom scales are the most discouraging piece of equipment in most men's houses. Not because they lie, but because they answer a question you did not ask, and they answer it loudly every single morning.

What the scales actually measure

Everything. Muscle, fat, bone, the water in your body, the food working its way through you, and how salty last night's meal was. You want to know about one of those. You get a single number that mixes in all the rest.

Day to day, most of what moves that number is water. Four pounds up overnight is not four pounds of fat, because four pounds of fat is roughly fourteen thousand calories and you did not eat those between Tuesday and Wednesday. It is a salty meal, a hard session, a bad night, or simply the normal wobble every human body does.

Why it is worse for men over 50 who are doing it right

Here is the trap. You start training. You begin building a little muscle back while losing fat. The tape at your waist moves, your trousers get looser, you can carry the shopping in one trip, and the scales sit there for three weeks doing absolutely nothing.

That is not failure. That is two changes happening at once and cancelling out on one crude measurement. It is also, reliably, the week most men decide it is not working and stop. They quit at precisely the point the thing is working best.

If you are going to weigh yourself anyway

Most men will, so do it in a way that gives you real information rather than a daily mood swing.

• Same conditions every time. Morning, after the loo, before food, no clothes.
• Weigh daily but never read a single day. Take the average of the week and compare it with the average of the week before. The wobble disappears and the trend appears.
• Judge nothing on less than three weeks. Two weeks of data on something this noisy tells you almost nothing.
• Expect one to two pounds a week at most. Faster than that and you are usually losing muscle too, which leaves you lighter, weaker, and far more likely to regain it.

A quiet word about body fat scales

The ones that send a small current through your feet and report a body fat percentage are guessing, and their guess changes with how hydrated you are. Useful for spotting a long-run trend if you use the same scales under the same conditions. Not worth a moment's thought day to day, and certainly not worth paying extra for.

The measurement that predicts the most

If you keep only one, keep the waist. A waist measurement creeping past half your height is the point at which it is worth acting, and it is a better guide to the fat that matters than weight or body mass index, both of which cannot tell a heavy, muscular man from an unfit one.

The change in my waist meant more to me than anything the scales did over the same period, and it took months rather than weeks. The scales did move in the end, but slowly, unevenly, and with several fortnights of doing nothing at all in the middle.

What to do this week

• Measure your waist and write it down with the date. Put a note in your phone for four weeks' time.
• Count your chair rises in thirty seconds. Write that down too.
• Either weigh daily and only read the weekly average, or move the scales out of sight for a month. Both work. Weighing daily and reading every number does not.
• When a number disappoints you, check the tape before you draw any conclusion.

Alex Jordan · Over 50 and Healthy