Why Am I Gaining Weight When I Start Rowing?

If you are gaining weight when you start rowing, the likely cause is extra water and stored carbohydrate in your muscles, or eating a little more than you realise, rather than new body fat. A rise of a kilogram or so in the first weeks is common and rarely means rowing isn’t working.

This is general information. If the gain is rapid or unexplained, or you have swelling in your legs, book a GP appointment.

Common causes, and how to tell

Cause	Typical size or timing	How you’d know
Glycogen and water	Up to a kilogram or so, first weeks	Rises soon after starting, then levels off
Muscle repair fluid	Comes with soreness	Heavier after hard or new sessions
Daily fluctuation	A kilogram or two	Bounces back within a few days
Extra food	Slow and steady	Keeps rising past week 4
Muscle gain	Small over a few weeks	Slow, and tape measure stays flat
Sleep and stress	Varies	Early starts, cravings, tiredness
Medication or a health condition	Varies	Rapid, unexplained or with other symptoms

Water and glycogen

Your muscles store carbohydrate as glycogen, and each gram holds roughly 3 grams of water. Training regularly can encourage your muscles to keep more of it. Here’s the sum: 200 g of extra glycogen brings about 600 g of water, so the scale shows 800 g with no fat gained. Those are illustrative figures, and the amount varies from person to person.

New exercise also stresses your muscles, and fluid gathers around them during repair. It typically settles as your body adapts.

Eating back the session

Rowing is hard work, and you may feel hungrier. It’s also easy to overestimate what a session used. Using the 2024 Compendium value for vigorous rowing (7.3 METs), a 70 kg person rowing for 20 minutes uses roughly 170 kcal. A large coffee and a pastry can easily cover that. “I rowed, so I can eat this” is a common thought. Occasional treats are normal, but when they become the pattern, the sums change.

Monitor calorie displays are estimates too, so don’t use them to decide how much to eat.

Muscle, sleep and recovery

Muscle. Beginners can add some muscle, particularly in the legs and back. Muscle is denser than fat, so it takes up less space per kilogram. Over a few weeks the gain is small, and it won’t explain a large increase. Our page on whether rowing will get you ripped covers what else affects muscle definition.

Sleep and stress. Short sleep and high stress are linked with changes in appetite and cravings. An early row that takes an hour off your sleep may backfire.

Too little recovery. Training hard every day leaves you sore, which can mean more fluid in the muscles and more fatigue-driven eating. Aim for at least two rest days a week at the start.

A four-week check

Do this before you change anything.

1. Weigh once or twice a week, at the same time and under the same conditions. Use the same scales, ideally first thing in the morning.
2. Compare monthly averages, not single readings. A swing of a kilogram or two between days means very little.
3. Measure your waist every two weeks in the same spot.
4. Track your rowing. Time a fixed 10-minute piece or 2k every four weeks. Our guide to measuring your results lists what to record.
5. Write down what you eat for 3 days, including drinks and snacks around sessions. This is for awareness, not restriction.

After four weeks	What it suggests	Next step
Weight up, waist same or down, pace better	Likely water or muscle	Carry on
Weight flat, waist flat	Food and activity are in balance	Review food, or add one session
Weight and waist both rising	Likely eating more than you’re using	Look at snacks and portions
Rapid rise or swelling	Needs a medical view	Book a GP appointment

Fuel and training

Eating enough before longer sessions supports recovery and can reduce over-snacking later. Avoid crash diets. They don’t suit training and can be harmful. If you want a plan, the NHS weight loss guidance includes a 12-week plan, and a registered dietitian can offer personal support. Our guide to your diet and rowing performance covers what to eat around sessions.

A mix of steady rows, some intervals and activity such as walking usually feels better than the same hard session daily. Our guide to rowing for weight loss shows how to build a routine and what the monitor can and can’t tell you.

What rowing won’t promise

Rowing can be part of managing your weight, but it doesn’t promise any particular result. The scale depends on food, sleep, stress, hormones, genetics and activity across the whole day. The same goes for how your body looks, as our page on whether a rowing machine will get rid of cellulite explains. For a realistic timeline, read how quickly you’ll see results. If your goal is fitness or strength, a better 2k may be a more honest measure than your weight. Further down the line, intense indoor rowing challenges give you a target that has nothing to do with the scale.

When to get medical advice

Book a GP appointment if you gain weight rapidly, have swelling in your legs or ankles, or feel short of breath at rest. Some medicines and conditions affect weight, so don’t assume it’s the rowing. Ask for help too if you’re becoming preoccupied with food or weight, or if exercise feels compulsive.