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Why did the scale go up when I started lifting?

Almost always water, not fat. Recovering muscles hold fluid, stored fuel comes with water, and your cycle adds its own swing. Give it a month and judge by the tape and the bar.

Woman standing barefoot on a digital bathroom scale, looking at her stomach in the mirror while checking her weight.
Reckoner Written by Reckoner

You did everything right. You started lifting, you turned up, you even began to enjoy it. Then you stepped on the scale two weeks in and it had gone up. If your first thought was that lifting is making you bigger, take a breath. That is almost never what is happening.

Your muscles are holding water while they recover

New training is a shock to a muscle, and a muscle recovering from a shock holds extra fluid. Researchers scanned the thighs of people new to lifting. By the third week the muscles measured bigger, but a large part of that increase may have been swelling from the training itself rather than new muscle, and it had largely settled by the tenth week1. That study was in young men, so take the detail as a guide rather than a promise.

So for the first few weeks some of the number on the scale is your body doing exactly what it should: patching things up so they come back stronger.

Fuel comes with water attached

Muscles store carbohydrate as glycogen, and glycogen does not travel alone. Each gram is stored with at least three grams of water2. If you have started eating a little more to fuel your sessions, which is a good idea, some of it shows up on the scale as water sitting in your muscles. That is fuel in the tank, not fat.

Your cycle moves the number too

If you have a menstrual cycle, it adds its own swing. In a year of daily diaries from sixty-two women, the feeling of holding fluid peaked on the first day of the period and was lowest in the days after the period ended3. That is one reason the number can wander across a month with nothing real changing. Compare like with like: the same point in your cycle, month to month.

What to watch instead

  • The weekly average, not the daily number. One weigh-in tells you about yesterday's dinner. Four of them in a row start to tell you about you.
  • The tape, once a month. A waist measurement says where a change went, which the scale cannot. How to take body measurements shows you how to do it so the numbers mean something.
  • The bar. If the weights you lift are going up, the training is working, whatever the scale says this week.

And if you are still worried about getting bigger than you want to, will lifting weights make me bulky? has the reassuring answer.

Give it a month. Watch the bar, not the bathroom scale.

Sources

  1. Damas F, Phillips SM, Lixandrao ME, and others, European Journal of Applied Physiology, 2016. Early resistance training-induced increases in muscle cross-sectional area are concomitant with edema-induced muscle swelling ten untrained young men over ten weeks: early increases in thigh muscle size came with swelling from training damage, which had settled by the end
  2. Fernandez-Elias VE, Ortega JF, Nelson RK, Mora-Rodriguez R, European Journal of Applied Physiology, 2015. Relationship between muscle water and glycogen recovery after prolonged exercise in the heat in humans muscle biopsies showing each gram of glycogen stored with at least three grams of water. Over five years old, and it confirms rather than replaces the long held figure
  3. White CP, Hitchcock CL, Vigna YM, Prior JC, Obstetrics and Gynecology International, 2011. Fluid Retention over the Menstrual Cycle: 1-Year Data from the Prospective Ovulation Cohort 765 cycles in 62 healthy women: self reported fluid retention peaked on the first day of flow and was lowest in the mid follicular phase. Over five years old
  4. NHS, NHS, 2026. Swollen ankles, feet and legs (oedema) when swelling needs a doctor, an urgent appointment or emergency help
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Did this answer the question you came with?
Myths

Will lifting weights make me bulky?

No. Muscle does not arrive by accident, and lifting tends to take a little fat off rather than pile size on. What you can count on is getting stronger.

 Tracking

How to take body measurements that tell you something

Body measurements answer the question a scale cannot. The scale gives you one number for two things that move independently. A tape says which one moved, and it only says it if you take it the same way every time.