Working out can cause short-term weight gain as your muscle mass increases. Post-workout inflammation may cause temporary weight fluctuations. Workout plateaus, supplement use, and dietary changes can also stall your weight-loss efforts. Try not to obsess over the number on the scale.

Water Retention After Exercise Since water weighs something, you may notice temporary weight gain after exercise. Don't get too concerned about this water weight, though, because it's not that you're gaining fat, which is what we're really concerned about when it comes to your health.