But youll bring those pounds right back on when you down that much water after your workout (which you should do), explains Robert A. Huggins, Ph.D., president of research and athlete performance and safety at the Korey Stringer Institute at the University of Connecticut. Its not fat mass, which is the weight most people have the goal of losing, he says.

Of course, over time, working out consistently can help you lose weight, but you cant judge how effective your workout is just by how much you sweat.

Shedding a lot of sweat isnt the main indicator that you worked hard. True, the harder you work out, the more youll sweat. But fluid loss doesnt tell you the whole story.

Each person has their own sweat rate, and it can change over time, says Huggins. So the guy next to you on the treadmill sweating buckets isnt necessarily outpacing you. On top of that, how much you sweat can depend on a number of things:

In order to do a quality workout that actually will burn calories or build muscle, you have to replace the fluid youre losing. Otherwise, your heart rate will go up and your body will likely slow down during that workout, which isnt going to help you get the weight loss workout you were going for.

Heres how it works: You have a set amount of blood that has to go to multiple places when youre working outit needs to go to your brain, your muscles, and your skin for cooling, Huggins says. When you sweat, your blood volume decreases if you dont replace the fluids youre losing. Your brain, muscles, and skin still need it, but now theres less to go around. So your heart rate increases, your workout feels harder, and youll probably slow down (or pass out if you really dont pay attention to what its telling you).

The ultimate way to keep your workout going during that session as well as day after day is to replace what you lost with this simple move, says Huggins.