Does Loss of weight reduce buoyancy ??

[Hillmorton Scubie]

After years of being around 210 pounds, I have spent the last 8 months getting down to a lean fit 170 pounds. Previously I have used 9 pounds of lead on my belt to sink with my full suit.
Will I find any difference in weight required on my belt,and if so, any idea how many pounds.
Or is it an old fable without scientific basis, that says body fat makes people more positively buoyant.

Thanks

 

[scc135]

Fat is less dense than muscle. More muscle mass and less fat = lower body density which makes you sink more than a higher body density. Can't really tell you how much lead you can take off, just jump in the water and test yourself out.

 

[Kronek]

Body fat does indeed make you float. Muscle makes you sink. So if you had a high percentage of body fat at 210, and a lower percentage now at 170. You will need less weight. How much? No idea. Do a weight check.

 

[conway400]

You are lighter, which makes you more bouyant. You should be smaller which would make you displace less water and be more negative. You are also denser, especially if you put on any additional lean tissue, so you would be more negative. Body fat, essentially oil, floats. Muscle, at about 75% water, does not float.

Since it so hard to adjust one variable without changing others, you know you should need less weight. But as others have said, you have to go try to see by how much.

 

[decompression]

Ok, seriously, the fat vs muscle really is more of a mistruth except in extreme cases. Human tissue is mostly what? Water. Is water buoyant in water? No. Yes, fatty tissue is less dense than muscular tissue but generally tissue is 60% water. The reason you can use your body weight to determine lead requirements is that it gives a rough size of exposure suit which is the greatest factor in lead requirement (research the concept of "balanced rig"). I wish instructors would be more thorough when discussing this topic. I'm glad a few agencies have embraced the "balanced rig" in their teachings as it would greatly assist people in diving safer. Bottom line, the reduction in your lead requirement will be minimal.

 

[DivemasterDennis]

Sorry to disagree with you decompression, but in my own anecdotal experience, as my weight of the years has varied from 195 to 220, the variable being fat, not added lean muscle mass, I find that changes of 8-10 lbs impact weighting by about a pound in salt water. Add 8 to 10 lbs of fat tissue, add about a pound of weight. Lose the same, drop the same. I think most people have a similar experience. Recently on an open water weekend (fresh water) we had a student diver who was in his mid 40's, about 6 feet tall, and weighed 275. He used 30 lbs in fresh water with a 7 mil full wet suit. We had another diver, about the same weight, but 6'6" tall with very low body fat percentage. He did just fine with 20 lbs in a 7mil full wetsuit, and could perhaps have used a little less. No way would the "rounder" diver been properly weighted at 20 lbs.
DivemasterDennis

 

[shmuggy]

Congratulations on the weight loss- quite an accomplishment! I have lost weight too and have found that in my case, it made only a slight difference so you need to get in the water all geared up before you start the dive and see what amount works best. After all, who knows what the ratio of fat to muscle is when we are losing weight.

 

[adutto]

After years of being around 210 pounds, I have spent the last 8 months getting down to a lean fit 170 pounds. Previously I have used 9 pounds of lead on my belt to sink with my full suit.
Will I find any difference in weight required on my belt,and if so, any idea how many pounds.
Or is it an old fable without scientific basis, that says body fat makes people more positively buoyant.

Thanks

Quick answer yes!

And as yo lost your "bioprenne" layer you can have thermal issues as well, that is, there is a chance that you get colder quicker.

Cheers!

 

[Teller]

Fat floats.

 

[GrumpyOldGuy]

Ok, seriously, the fat vs muscle really is more of a mistruth except in extreme cases. Human tissue is mostly what? Water. Is water buoyant in water? No. Yes, fatty tissue is less dense than muscular tissue but generally tissue is 60% water. The reason you can use your body weight to determine lead requirements is that it gives a rough size of exposure suit which is the greatest factor in lead requirement (research the concept of "balanced rig"). I wish instructors would be more thorough when discussing this topic. I'm glad a few agencies have embraced the "balanced rig" in their teachings as it would greatly assist people in diving safer. Bottom line, the reduction in your lead requirement will be minimal.

The simple answer is fat is about 90% the density of fresh water, so you might be able to drop 4lbs (10% of 40lbs) in f/w.

Oh, and congrats to the OP for the weight loss!