Weight Gain Due to Heat?

Below is a response to the question about weight gain (without any dietary changes) experienced during heat/humidity. I found this very interesting. I feel it answers my question of the scale fluctuation over the past few weeks. I have found myself waking up the past few mornings with very puffy eyelids, stuffy nose (swelling in sinus cavity), and just generally feeling like a big ol' fat tick!

That’s not your imagination. A significant portion of the human body is water. When the weather is hot, body weight can go up by several pounds due to increased body water.  In warm weather, fluid-conserving hormones kick in which allow the kidney to retain more fluid…and reduce the amount of salt in sweat, leading to even more water retention. Water retention accounts for many day-to-day fluctuations on the scale. We tell our clients year-round, and especially in the summer months, that a gain is not actually a gain unless the scale goes up 2.5 pounds or more, as daily variances in water weight can account for that much (possibly more).
Have you ever noticed how quickly swelling can happen in warm weather? You might be inside in air conditioning and your rings are loose, and then step outside into the heat and your rings are suddenly stuck on your finger. It’s a natural reaction to the change in climate. Heat edema is a swelling of the extremities associated with exposure to high temperatures (commonly during heat waves or when someone accustomed to more temperate climates travels to a warmer climate).
As a reminder, it’s best to weigh yourself once a week at the same time each week to avoid getting discouraged by any day-to-day water retention variances. And, it’s always good to remember that the scale isn’t your only measuring tool. How your clothes fit, your energy levels, how you’re sleeping and how you’re feeling overall are great indicators of the positive changes that are happening within. We’re glad to hear the program is going well for you…now put the scale away for a while, step into the A/C and relax with a cold glass of ice water.