While most experience some weight shifting through the seasons, especially here in the Northeast where distinct and sharply contrasted climates cause a sort of hibernation at times, and binge around the holidays to fatten up for the winter cold; this weight change is overwhelmingly apparent when my busy dive season kicks into gear.
I can't help but attribute this to the extreme environmental conditions I am exposing my body to. For instance, each and every day, all winter, I go from bone chilling cold while topside, to donning a hotwater suit and sweating like a fiend while working hard for a full day - immersed in hot saltwater. Water weight alone shifts daily by several pounds.
These extremes cause a very real 'metabolic mayhem'. While working hard, my body is breaking down its energy stores in a radical way. When I stop for the day, or for an extended period of time, I'm on shutdown. My body recognizes that I'm taking a break, and the pounds pack back on - stores for the next high stress work period. The unfortunate times are when I actually do catch a break - the excess seems there to stay.
Recently, I tracked my body weight shift over the course of a 3-week dive project. My weight swung 4 pounds daily from teh AM before work, to the PM before bedtime. Over the 3 weeks, I lost a total of 7 pounds. Then, after 2 weeks off, I was back to my +7 (and then some). Thankfully I'm back on the job!
On top of the physical and physiological stressors of diving that we routinely discuss, our body adapts to the extremes in some incredible ways. Metabolism is just a small part of the story, though one we should certainly be paying more attention to as working divers.