Surely firstly it depends on how much weight you lose? Secondly fat is going to aid buoyancy, so if you lose fat you might end up suffering technique wise even if you benefit CV wise.

Agreed. Losing weight by reducing your belly fat does not only affect your density, but also changes your center of gravity.

The less fat percentage I have, the slower I'm in the pool but the faster while running or cycling. My legs, especially quads, weigh too much compared to my torso's "buoyancy" and alignment/position

I'm no expert at all on swimming, but my weight doesn't seem to impact swimming much. In fact, I'd say I'm a touch slower when I am lighter.

I've recently gone from 5'9" 158lbs to 145lbs in around 9 weeks, so 1.4lbs/week lost. I'm less buoyant, but no noticeable decline in speed. I am more resilient in terms of lower HR and don't get gassed being more fit, so that is a benefit at least for me.

I am guessing that you are a woman? Females seems to get some aid in their body position by excessive fat. Males do not.


Probably. And i guess there is not a linear relationship between weightloss and speed but being a male, with most excessive fat on my upper body, I would gess that my body position would be better, not worse.

Interesting. Does your alignment in the water change? Do you feel weaker?

Nope, I'm a man but I'm talking going from already low fat percentages (10-12%) to really low fat percentages (6-9%)

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x2 although I stay the same speed +/- 20lbs.
As a technique sport you can't look at someone and have any idea how well they swim.
Old and fat could still swim circles around me while young and buff could fail to make it 25 yards without stopping.

Fitness and amount of training meters for swimming are irrelevant if technique doesn't change.

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Swim - Bike - Run the rest is just clothing changes.

If your technique is good, you don't lose too much strength during the weight lose, you'll be faster when lighter.

Tim

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This one is a lot harder to answer than the running one due to changes in buoyancy. I don't have a good answer for you, but at least Olympic male swimmers look pretty lean.

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maybe she's born with it, maybe it's chlorine
If you're injured and need some sympathy, PM me and I'm very happy to write back.
disclaimer: PhD not MD

It is a bit different than running because of gravity, but some things are the same. It is true that more fat = more buoyancy, and I have felt over the years that it was not much of a disadvantage to be 10/20lbs overweight. But the problem with this is that fat is not a buoy, it is actual tissue your heart has to pump blood to, and your body has to keep it alive.

I just recently lost a bowling ball of that weight, and the positive affect to my cardio was noticeable. And it outweighed any loss of buoyancy, and in the aggregate I became a faster swimmer. As someone pointed out, most your top male swimmers are in that super low body fat range, so all arrows point to that being the most productive weight for swimming.

They certainly do, but I would say that they do not look as lean as their counterparts in other endurance sports at the olympic level. I wonder if it has anything to do with thermogenics of them doing all their (alright most) training in the water where heat loss kinetics are so different from cyclists and runners

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USAT Level 1 Coach
Team Next Level
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definitely true

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maybe she's born with it, maybe it's chlorine
If you're injured and need some sympathy, PM me and I'm very happy to write back.
disclaimer: PhD not MD

I tend to be bit weaker in the upper body when I am lighter. When I am heavier my body seems to put on upper body muscle more easily.

If I try to lose weight I drop some fat and upper body muscle first. So if I get lighter I have to make sure I keep swimming up or I will get slower. This is opposite to running, losing weight ties really well with getting faster.

My theory is Katie Ledecky got slower in her distance events in the Olympics due to all the extra mass/muscle she had over Rio. you need a lot of extra oxygen to fuel extra mass in distance swimming, but fat is buoyant and muscle offers leverage. Certainly in short events bigger is gonna be better, but distance there is a trade off.

I think for tri swimming with wetuit, where you get all the buoyancy you need from wetsuit, there is zero benefit being bigger. Lighter is better since you have to support less mass with same oxygen, and have all the buoyancy from suit (and tri swimming is distance swimming) and of course less mass for bike-run is always good.

In my swim club the same swimmers who smoke me at all strokes at 50-100m, I can draw even at 200m and I am faster 400m-1500m. I am literally the smallest male racing at local/provincial/nationals (5'6", 140-145 lbs). Everyone seems to be 20-80 lbs heavier and 4-12 inches taller. And 145 lbs 7-8 lbs over my tri race weight

They certainly do, but I would say that they do not look as lean as their counterparts in other endurance sports at the olympic level. //

Well that is not fair, as you cannot compare running and cycling athletes who have to fight gravity, to swimmers who do not. Now if you compare them to rowers/speed skaters/ skiers, or other non gravity endurance folks, then they will be very similar in builds and size.

Nitpick, but nordic skiing is a gravity challenged endurance sport. It has (especially on the womens side) problems with eating/weight issues for the long distance practitioners.

Nitpick, but nordic skiing is a gravity challenged endurance sport.//

Well when I said skiing, I meant downhill of course. Nitpick noted...

As others have said, a couple pounds doesn't make a drastic difference, but it all depends. If the extra weight is all around your belly and it changes the shape of your body through the water (increased drag), then obviously that's bad, but if it is in your legs, well then maybe they float better and that reduces drag.

The one absolute in terms of swimming and losing weight is that you will be faster when you need to shift that weight fast, so off the blocks and off the walls. For open water swimming these actions don't happen.

If I compared myself to 20 years ago when I was just a competitive swimmer, I'm not that much heavier (~10lbs), but I have significantly more developed/denser calves, hamstrings, etc from running and cycling, so I don't think I could ever regain the swim speed I had then with the body I have now, even if I were to focus only on swimming. (I could swim ~8s/100y faster 20 years ago)

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Do some research before shooting for that low bf%. As a former body builder I’ve seen quite a few metabolic screw ups from some attempts to get into a low range.

Strength and fitness matter way more than weight

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"The person on top of the mountain didn't fall there." - unkown

also rule 5

Agreed. When leaner/lighter I swim slower but run faster. Took time off from training got a little fattter and was faster in the water than when I was swimming 3x a week and running and cycling. I know I was not fitter