It can be incredibly disheartening to diligently stick to a workout routine, only to find the numbers on the scale creeping upwards. You might find yourself questioning, “Why Am I Gaining Weight While Working Out?” especially if you are also mindful of your diet. Seeing a higher number on the scale, when your goal is weight management or even weight loss, can be frustrating. However, it’s important to understand that gaining weight while exercising is not always a step backward and can often be attributed to several normal physiological responses to physical activity.
Here are four evidence-based reasons why you might be gaining weight even when you are working out and maintaining a healthy eating pattern.
Water Retention After Exercise
Thinking about that intense cardio session and the potential pounds you might have shed? While you do lose water through sweat during exercise, rapid weight loss immediately after a workout is often just water loss. Conversely, if you notice the scale reading higher, it could be due to water retention, a common occurrence post-exercise.
According to clinical exercise physiologist Jeffrey A. Dolgan, “Water makes up approximately 65 to 90 percent of a person’s weight, and variation in water content of the human body can move the scale by ten pounds or more from day to day.” This highlights how significantly hydration levels can influence your weight.
Hormones also play a role in post-exercise water retention. Research indicates that temporary water retention is quite normal, particularly for women in the pre-menopausal stage and those who menstruate. This hormonal influence on fluid balance can contribute to weight fluctuations observed on the scale.
Key takeaway: Your body’s water content is a major determinant of your weight. Diuretics, while popular for quick weight loss, only reduce water, not body fat. Therefore, scale readings can be misleading when solely focusing on weight changes immediately after exercise.
Weight Gain Immediately After a Workout
It’s not uncommon for the scale to show an increase immediately following a strenuous workout, or even in the subsequent day or two. This is generally normal and doesn’t necessarily signify actual fat gain, as explained by Dolgan.
“A person’s scale mass is a combination of muscle, fat, bone, the brain and neural tract, connective tissue, blood, lymph, intestinal gas, urine, and the air that we carry in our lungs,” he clarifies. “Immediately after a workout routine, the percentage of mass in each of these categories can shift as much as 15 percent.”
Intense workouts cause these scale variations due to several factors. These include your hydration status, inflammation resulting from muscle repair (known as delayed-onset muscle soreness or DOMS), and even changes in intestinal by-products, urine volume, and blood volume, says Dolgan. Research supports this, documenting significant fluctuations in fluid retention, inflammation, and swelling after events like ultra-endurance triathlons and multi-day cycling races.
Therefore, if you are experiencing weight gain while exercising and eating well, it might not be the type of weight gain related to increased body fat.
Gaining Weight Working Out from Strength Training and Muscle Growth
“A frequent misconception when looking at the scale is that ‘muscle is heavier than fat,’ which is actually misleading,” Dolgan points out. “A pound of fat weighs the same as a pound of muscle; however, muscle tissue is denser than fat tissue, meaning it occupies less space for the same weight, and therefore, has a greater density.”
Recent research emphasizes that when you begin to alter your body composition through exercise—specifically by building denser muscle mass and reducing body fat—your weight on the scale might increase, even as your body fat percentage decreases. Dolgan mentions that these compositional changes happen over longer periods, weeks to months, not within days or hours, making the scale an inadequate tool for tracking these specific changes. Considering this, weight gain alongside exercise, particularly strength training, is a common and often positive sign.
Weight Gain from Muscle Versus Fat and the Limitations of the Scale
The scale alone cannot differentiate between muscle and fat mass. Therefore, it is not the most effective tool for measuring progress if your primary goal is to improve your overall fitness. Furthermore, fixating on the number on the bathroom scale, especially when fat loss isn’t the only objective, can lead to unnecessary worry and questions like, “Why am I gaining weight?”
“If someone is focused on enhancing their fitness, they should ideally look beyond the scale and utilize more objective measurement tools such as body composition analysis to accurately monitor their progress,” advises Dolgan.
While weighing yourself can be one metric to monitor progress, it should not be the only one. Dolgan reminds us that simply losing weight on the scale doesn’t automatically equate to improved fitness—it merely indicates a reduction in body mass.
It’s important to remember that if you are exercising and observing weight gain, it could be that your workouts are indeed effective in building muscle, but other elements such as certain medications, calorie intake, or underlying health conditions may also be contributing to weight gain. If your primary goal is weight loss and you’re concerned about weight gain, consulting with a healthcare provider or a registered dietitian can provide valuable personalized guidance and support.
