Weight Loss and Buoyancy (or lack of)

[MrChen]

I recently changed up my diet and lost 20 pounds in the last 3-4 weeks. I did a dive this last weekend and I just didn't feel as comfortable with my buoyancy in the shallow waters of BHB (Blue Heron Bridge). I felt heavy and had to constantly fidget with my BCD inflation.

So I was 275 lbs and carried 16-18 lbs with an AL80. Now I'm 255 and will probably be in the upper 240's by the end of this week. Obviously I need to start decreasing my weight carried. With a Steel 100 I typically carry 10 lbs. My next dive this Friday will be on a drift dive in Jupiter and I wonder if I should dive 8 lbs rather than 10. The buoyancy won't be as difficult at depth as the shallower BHB, but I'd like to start adjusting my carried weight as I lose body weight.

Any tips are appreciated, thanks.

 

[victor]

Points,
1. You need to do a propper weight check with a near empty tank
2. 5 lbs a week is aggressive, this will affect your energy levels so be careful.
3. If diving wet then your suit is not going to be a great fit. Be careful about getting cold see point 2.

 

[Lorenzoid]

Keep in mind that the relationship between a person's body weight and buoyancy is not entirely straightforward. A given volume of fat weighs less than the same volume of muscle since it is less dense. So losing fat and replacing it with muscle would decrease the body's net buoyancy. (With such rapid weight loss, I doubt you're replacing it with muscle.) But positive buoyancy depends on the volume of water displaced, so it's how much less you displace now that you've lost weight that counts. And if you're still wearing just as much neoprene over the surface of your body, well, that would be a big factor, too.

I realize this is not your question. You'll just have to experiment.

 

[decompression]

Start with how much weight does it take to sink your wetsuit and BCD? Do a balanced rig equation and that'll get you in the ball park.


Sent from my iPhone using Tapatalk

 

[MrChen]

I'll probably just dive the 10 lbs on the drift since I don't want to become buoyant. I'll play with it on my AL80 at BHB before I do so on a drift dive off a charter. A failure to descend on a charter would ruin the dive. At the bridge I can just walk back to my car. Thanks for the advice.

 

[redacted]

Body fat is less dense than water. It seems to vary a bit but is in the range of .91 to .94. So, you should need to drop a pound of lead for each 12 to 16 pounds you lose. You could surely drop one pound and probably two. Two might be a bit much but should be manageable, especially in SW. Congrats

 

[DivemasterDennis]

I agree with awap's "guideline." But the most important thing is to record your weight and weight used on each dive, as well as the equipment you used, especially tank size and type and exposure suit. Note any comments on your buoyancy. You should end up with a good "chart" of proper weighting based on those factors. I have bounced between 200 and 222 since I have been diving, and so find that reference and history very useful.
DivemasterDennis

 

[Tony387]

Body fat is less dense than water. It seems to vary a bit but is in the range of .91 to .94. So, you should need to drop a pound of lead for each 12 to 16 pounds you lose. You could surely drop one pound and probably two. Two might be a bit much but should be manageable, especially in SW. Congrats

I agree with AWAP's estimation. I lost over 100lbs over the period of about a year, and I went from wearing about 16-20lbs in fresh water, (5mm all the way around) to diving with a steel backplate and no weight at all. Figuring out your new weighting requirements is an easy fix. The difficult part is keeping a wetsuit that fits. I also moved to BP/W, among other factors, because of the ability to adjust the harness as you continue to lose. Congrats on your weight loss, and keep up the good work.

 

[MrChen]

Body fat is less dense than water. It seems to vary a bit but is in the range of .91 to .94. So, you should need to drop a pound of lead for each 12 to 16 pounds you lose. You could surely drop one pound and probably two. Two might be a bit much but should be manageable, especially in SW. Congrats

Thanks, that's more of what I was looking for. I felt heavy on my last dive carrying 18lbs with my AL80. I know I can dive 16 and feel slightly buoyant when my tank gets under 800. I could probably do 16 no problem now. I know most recommend dropping 6 lbs going to a steel 100, but 10lbs has always worked great for me. But now with the weight loss, I want to consider going to 8. I'll hold off though until I lose another 10-15 lbs.

---------- Post added April 14th, 2014 at 12:43 PM ----------

I agree with AWAP's estimation. I lost over 100lbs over the period of about a year, and I went from wearing about 16-20lbs in fresh water, (5mm all the way around) to diving with a steel backplate and no weight at all. Figuring out your new weighting requirements is an easy fix. The difficult part is keeping a wetsuit that fits. I also moved to BP/W, among other factors, because of the ability to adjust the harness as you continue to lose. Congrats on your weight loss, and keep up the good work.

Thanks Tony. If my BCD ever feels large, it might be the time for me to jump to BP/W. It's in my future plans, I just have other gear priorities I want to take care of.

---------- Post added April 14th, 2014 at 12:44 PM ----------

I agree with awap's "guideline." But the most important thing is to record your weight and weight used on each dive, as well as the equipment you used, especially tank size and type and exposure suit. Note any comments on your buoyancy. You should end up with a good "chart" of proper weighting based on those factors. I have bounced between 200 and 222 since I have been diving, and so find that reference and history very useful.
DivemasterDennis

I'll start doing that, thanks.

 

[djtimmy77]

Eat more donuts, fried chicken, doritos, etc and then you won't have this issue!

Congrats on the weight loss though, I'll probably get on that wagon in the next month or so. Will just have to do a lot of BHB dives to sort out the dive weighting.