Weight loss from diving in cold water

[tlawler]

If you're exercising hard enough to cause any significant weight loss, your breathing rate will be thru the roof relative to any normal dive, and you will blow thru a tank in no time flat. Swim laps at the surface.

What I usually do is swim out on a straight line for approx 40 minutes at a fairly leisurely pace, then turn and swim a reverse bearing. At the 40 minute mark, I'm starting to feel a little chilled and by increasing my fin cycles to 2 or 2.5 times my previous pace, it puts my heart rate up into my optimal cardio range of 140 to 150 bpm and I'm not really breathing too hard, steadily, but never near the point of being breathless. It takes me about 15 to 18 minutes on the return leg for a total dive time of just under 60 minutes. On the way back, I definitely have a sensation of being less chilled, even warm near the end of the dive. I dive a steel 72 and if I'm just leisurely swimming and hunting sharks teeth, it will last between 95 and 105 minutes, so I'm only shortening my dive by 30 minutes or so. Fills are cheap at less than $2.00 for me and I find it quite enjoyable and satisfying.

Your body does not have a real-time mechanism for increasing metabolic rate. If core temperature starts to fall, the first response is vasoconstriction to reduce peripheral heat loss, and when further drops occur, shivering ensues. Shivering is extremely inefficient muscle activity and burns a lot of calories, and produces a fair amount of heat.

If your core temperature falls, but not enough to cause shivering, you will slowly rewarm post-dive as a result of your normal metabolic processes, combined with the vasoconstriction (and probably with your donning of warm, insulating clothing as well). There's no increased calorie usage involved.

Lynne, thanks for giving us a professional perspective on the subject. I was hoping you would see the thread and contribute to it.