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You started running to lose weight, but instead of seeing a smaller number on the scale, you have gained a little. It is one of the most common and demoralizing experiences for a new runner, and it makes a lot of people quit before they see any real progress.
This article explains why the scale goes up when you start running, and what to do about it.
Is it normal to gain weight when you start running?
Yes, a small change in body weight can happen when you start a new running routine.
Seeing the scale move up and down during the first weeks of training is very common. New training changes how much glycogen and water your body stores, adds muscle tissue, and can shift your appetite and daily activity. All of these affect the number on the scale, which is why it rarely holds steady. And that does not mean running is not working, or that you are doing something wrong.
So why might your weight go up after you start running? There are several common reasons.
Why the scale goes up when you start running
1. Your muscles store more water
As you train, your muscles store glycogen, the carbohydrate they use for fuel. Each gram of stored glycogen is associated with about 3 grams of water, so increased glycogen storage can raise body weight without adding body fat.
2. Sore muscles can hold extra fluid
Hard or unfamiliar exercise causes temporary muscle damage and inflammation. The resulting changes in fluid balance can contribute to short-term increases on the scale. This effect is usually temporary.
3. You may slowly build muscle
Beginners may gain some muscle in legs and hips as they adapt to training. This is usually a slower process than changes in water and glycogen.
4. You may eat more or move less elsewhere
Running may increase hunger, and some people unconsciously compensate by eating more. They may also do less physical activity during the rest of the day. Research reviews suggest these compensatory responses are common enough to reduce the expected effect of exercise on body weight.
Is it water, muscle, or fat?
A basic bathroom scale shows one number and cannot tell water, muscle, and fat apart. That is why the number alone misleads so many runners.
If you want to see what is really changing, a body-composition test now and then, such as a DEXA scan or an InBody reading at a gym, can tell these apart and show what your weight is made of. Home bioimpedance scales try to do the same, but their readings swing with hydration and timing, so their estimates are not that precise.
In the first weeks, the most likely answer is water. A jump of a pound or two over a day is almost never fat, since gaining that much fat would take a large calorie surplus. Water rises after hard runs, with sore muscles, and with a salty meal, then settles again as your body recovers.
Muscle gain can also contribute to a gradual increase in body weight, especially as a beginner. But this usually happens more slowly than changes caused by water and glycogen.
Fat gain is possible too, but mostly if running makes you hungrier and you regularly eat back the calories you burn, or more. Exercise on its own does not guarantee a calorie deficit, and in studies people often eat more and move less the rest of the day, which cancels out much of the loss they expected.
For women, the menstrual cycle can also cause temporary changes in body weight. Hormonal changes can increase water retention around the time of the period, which may push the scale up for several days. The extra weight usually falls as the cycle progresses.
What to do about it
Gaining a little weight when you start running is common, and it does not always mean you are gaining body fat. Early changes in glycogen, body water, muscle tissue, appetite, and daily activity can all affect the number on the scale. So don’t quit running just because your weight has not dropped yet.
If your goal is weight loss, you still need a sustained calorie deficit over time. Running can help create that deficit, but it does not guarantee weight loss on its own. Focus on balanced meals, reasonable portions, enough protein and fiber, and avoid strict diets or using your runs as a reason to regularly eat far more than usual.
Give your body a few weeks to adjust. Instead of judging your progress by a single weigh-in, look at the trend over time and also pay attention to how your clothes fit and how you feel. The scale is only one measure of what is changing in your body.
And if the weight still will not move, our guide on what to change to start losing weight with running lays out the exact habits that get results.
