Why Your Weight Goes Up When You Start Exercising Before It Goes Down

As if the looming impacts of climate change and other assorted threats to Earth weren't enough to worry about, there's also a major health crisis to contend with — especially in the United States. The ongoing overweight and obesity epidemic has been placing an increasing burden on the health of the U.S. for several decades, and it's only projected to get worse.

A 2024 study published in The Lancet noted that, in 2021, an estimated 15.1 million children and young teenagers, 21.4 million older adolescents, and 172 million adults were overweight or had developed obesity. What made those figures even more alarming was the fact that, between 1990 and 2021, the prevalence of obesity had increased by 158.4% among male adolescents, 185.9% among female adolescents, 123.6% among male adults and 99.9% among female adults. At those rates, the researchers predicted an additional 3.33 million children and young teens, 3.41 million older adolescents, and 41.4 million adults will become overweight or develop obesity by 2050. That means that by the halfway point of this century, almost 260 million U.S. residents are predicted to be overweight or obese.

It's not the most encouraging picture, which is why it's more essential than ever to keep an eye on our weight and try to maintain a healthy lifestyle. But as anyone who's tried will know, losing weight is not an easy process — especially when we stand on the scale and notice it goes in the opposite direction to what we'd hoped. Putting on weight while exercising is a real phenomenon and can be discouraging. But there is a perfectly rational explanation which, thankfully, reveals such weight gain is only temporary.

It's not all that pleasant to hear that our modern lifestyle has caused us to develop habits that will make us die early. But that is, unfortunately, the bleak picture we face. Thankfully, there are things we can do to fight back, and exercising is one of the most important. There are lots of reasons to exercise, and working out should be a part of our lifestyle no matter what. But it's no secret that a large number of people turn to exercise in order to shed some extra pounds. Doing so, however, is tricky.

What's the best way to lose weight? Is it better to count calories, burn calories in hot or cold weather, cut out carbohydrates, fast intermittently, do as much cardio as possible, or just try to get a bit of extra walking in? Well, there's never been any secret to losing weight beyond a healthy diet and regular exercise, though different methods will work better for different people. Frustratingly, exercise by itself can often cause us to actually gain weight, but don't panic if you see yourself putting on pounds when you start working out.

When we work out, we're pushing our bodies, which require extra energy in order to match the demands we're placing on them. As such, our bodies start to store glucose reserves, in the form of glycogen, in order to fuel our muscles for future workouts. Glucose of this sort is essentially what muscles use as energy. During exercise, muscle glycogen particles are broken down, allowing glucose molecules to be used for muscle contraction. When we start exercising, then, our bodies store glycogen, which, due to the fact it binds with water, can add 1 to 3 pounds of water weight to our overall weight.

It might seem counterintuitive that we actually put on weight when we start exercising, and it's certainly a frustrating aspect of the workout journey, but the good news is that the glucose storage–induced weight gain doesn't last for long. In fact, it should only remain a factor for a few weeks to a month.It's also worth bearing in mind that other factors can contribute to weight gain during exercise. The fact that muscle is denser than fat, for instance, means that as we gain muscle and lose fat we may notice ourselves weighing more due to the fact the muscle is heavier than the fat we burnt.

There's also inflammation to consider. Building muscle through exercise involves making micro tears in our muscles, which the body then attempts to repair via inflammation, which involves retaining fluid around the micro tears. This water retention adds more weight to our bodies, though this is even more short-lived than the glucose retention, with inflammation typically disappearing within a day.

There's no doubt losing weight is a difficult task, and it doesn't help that our bodies are literally designed to fight weight loss by storing and retaining calories as fat. With that, and the various ways in which our bodies actually put on weight during and after exercise, in mind, it's important to remember that watching the scale isn't always the best approach.