Yes on my long runs I will weigh myself afterwards so that I know how much weight I lost so I can calculation how much hydration/sodium I need to replenish what I lost. I only record the weight I am first thing in the morning nude before my shower.

@mnemonicone3 Minor dehydration will cause your body to store water resulting in higher numbers on the scale. Unless you are pouring/dripping sweat AND not rehydrating during your workout, you will probably see higher numbers on the scale. Personally, I won't go near my scale at any other time of the day other than first thing in the morning. That's it. Even one cup of coffee will bump me up a pound. And, if you're like me, you're probably grabbing a few sips of water every time Autumn says "grab some water if you need it."

Another possibility are muscle tears. Everything we're doing in 21DF includes some form of strength training so we're tearing down those muscles. Part of the healing process includes the body's natural means of repair--glycogen. Glycogen and water retention go hand-in-hand. It's natural.

These and probably a few other reasons are why you're trainers in the past have said not to weigh yourself after a workout. They understand what may happen and the potential impact it may have on your mental state regarding exercise. If you can't resist weighing yourself after a workout and you are finding it discouraging to see that you've gained, then give your scale to a friend, neighbor, anyone, and don't get on any other scale until you wake up on day 22 and weigh yourself to see just how successful you've been while doing 21DF. If you can weigh yourself, see an increase, and shrug it off, then no worries.

OMG! Someone shoot me! I used you're instead of your!!!

@mnemonicone3 If you have a Fitbit and a wifi scale, I've heard good things about this site: https://trendweight.com/

Apparently, this site tracks your weight over time and looks for trends (hence the name) such as water retention and time of month fluctuations. But you'd have to sort of commit to not weighing more than once a day and not give into disappointment if the numbers are not steadily going downward. I don't have either a fitbit or a wifi scale but I've been tracking my weight for a looooong time, and I am okay when I see what I know are normal body changes.

Don't get me wrong. If I am unhappy about something else--maybe frustrated with my job search, wake up with more joint pain than usual, or my husband is irking me--and I see larger numbers on the scale, it can and will make me feel pouty. I'm just as good at throwing a Pity Party as the next person. But I guess it's about power and I really don't want to give my emotional power over to my scale.