Weight loss plateau: what's really behind it.

On Monday morning you step on the scales and see last Monday's number. That's a weight loss plateau, and it nearly always shows up the same way. You've stuck to the plan and the needle won't budge.

A question I often hear: am I still paying for that blowout, or am I doing something wrong? Usually neither. And eating even less is the least helpful move.

Is a week of not losing weight normal?

Yes. Weight comes off in steps, and one flat week on its own tells you nothing. It counts as a plateau when weight and measurements stay the same for two to six weeks.

• Flat after an unusual week. Travel, dinners out, hot weather, short nights. Your body holds fluid.
• Flat around your period. You hold more water before and during. Compare with the same week last month.
• Weight not moving for a month, measurements included. That's a real plateau.

Why has my weight loss stalled?

Fat comes off slowly. Water comes and goes quickly, and can hide fat loss on the scales for days.

A theory: water in place of fat. Sometimes weight stays flat for one, two, even three weeks then starts dropping again. One suggested explanation, not proven, is water held by the fat cell as it empties.

Salt and carbs. After a saltier dinner you hold fluid. An extra plate of pasta tops up the sugar store in your muscles, where each gram brings about three grams of water. A big weekend is usually water too, for a few days.

Stress and short nights. Cortisol, the stress hormone, can make you hold fluid, and after short nights the scales tend to read higher. So when weight stops coming off, look at your sleep first.

Muscle. If you lift weights and have a kilo or two to lose, you may add a little muscle while losing fat, so your weight stays put. With ten to go, the scales should come down too in time.

What to track instead of the scales

Your waist. If the tape is coming down and your weight isn't, you're usually losing fat. My article on waist size explains how to measure.

Strength and hunger. If your gym weights are holding or going up, that's a good sign for your muscle. And each week, check your hunger, your energy, your sleep and your mood by evening.

The same weigh-in every time. Once a week, in the morning after the loo and before breakfast, on the same scales in the same spot. Two scales can differ by half a kilo.

What you don't count. When a plateau is real, the most common cause is tastes while cooking, oil poured by eye, the glass of wine. My article on eating less but not losing weight covers it.

Most people hit a plateau at some point, including those who get there in the end. Give it two weeks without touching your plate, then look at everything together. If tape, strength and scales are all flat, adjust one thing at a time.