I know this can be very different from one person to the next but are there any formulas out there to show a general idea of how much speed you can expect to pick up on the bike and run based on a certain amount of weight loss (assuming this is mostly fat loss and not muscle).
I am doing my second IM this year and want to go for a certain time on this one as opposed to “just finish”. I am currently 5’10’’ 180 lbs and about 20% body fat. Currently my max bike is around 21mph for a 20-30mi ride and max run would be around 7:30 - 8:00 Min/Mile for a 5-10k. My goal race weight by the beginning of the summer this year is 170lbs which I haven’t been at since I was 16 years old.
Any ballpark predictions out there on how much dropping 10lbs will increase my speed on the bike and/or run? I realize there are many factors that could go into this. I am not looking for exact #'s, just seeing if anyone else has been in this situation and after dropping some weight, realized a certain amount of increase.
Running is a power to weight sport, so speed will increase roughly proportionally to fat weight loss (i.e. going from 180 to 170 you will get ~6% faster). For biking, there will be very little gain on the flat since that is proportional to frontal surface area (which won’t change much). Cycling gains when climbing will be somewhere in between. There will be little to no change in swimming (top swimmers are lean because they work out 7 hrs. a day, not because being lean makes you faster).
Now the qualifier: The above is only an approximation, because when people lose weight there is almost always a change in body composition. It would be natural to see some muscle loss as part of the weight loss if it was purely caused by calorie restriction. If you are losing weight by working out more then there is a change to the fitness baseline in addition to just being lighter. As in all cases, your mileage may vary.
As a college runner at 6’3" 165lbs I was running 28:45 for the 8k in cross country (slow!!!). With the same training/mileage, the next season at 150lbs I was running 26:30 simply on weight loss alone. It works for running, that’s a no brainer. Not as simple for swim and bike.
Normally you can guess about 2 seconds per mile per pound of lost extra weight for a 5k race. That does not include muscle loss. So a 10 pound fat loss should equate to a 15 to 25 second per mile gain in speed over a 5k.
As a college runner at 6’3" 165lbs I was running 28:45 for the 8k in cross country (slow!!!). With the same training/mileage, the next season at 150lbs I was running 26:30 simply on weight loss alone. It works for running, that’s a no brainer. Not as simple for swim and bike.
6’3" at 150 lbs…can you say underweight? Seriously…that is just skin and bones dude. I’m 6’3" - 165 lbs and if I lost anymore weight due to training, I would stop.
Yea let’s just say I wouldn’t have won any fist fights then ;). I didn’t plan on losing the weight but worked at a sports camp in Missouri for a month (100 + degrees and humidity, sweating all day). I came home and was running great. Then I weighed myself and found out why. I was down 12 lbs. The next year I cut out all late night snacking, cut out salad dressings, cheeses, etc and ate much healthier and decreased calorie intake to stay thin. It worked for college running; you can see why a lot of runners are walking a fine line close to being too thin, bc walking as close to the line as possible without stepping over can lead to big results. Step too far and you’ll get sick, injured, etc.
As a college runner at 6’3" 165lbs I was running 28:45 for the 8k in cross country (slow!!!). With the same training/mileage, the next season at 150lbs I was running 26:30 simply on weight loss alone. It works for running, that’s a no brainer. Not as simple for swim and bike.
6’3" at 150 lbs…can you say underweight? Seriously…that is just skin and bones dude. I’m 6’3" - 165 lbs and if I lost anymore weight due to training, I would stop.
No kidding…even @ 6’4" 178 my wife said I was looking gaunt and wasn’t allowed to go any lower. I’d still love to race at 175 though.
also, for what it’s worth, VO2 max is a function of body weight. (ie., it’s measured PER kilogram.) so you can increase your VO2 max without strictly speaking increasing your ‘fitness’ simply by losing weight. same ‘fitness’ at lower body weight = higher vo2, just like higher fitness at same body weight = higher vo2.
So in my marathon training which is currently on hold, I can get faster by just losing weight? Man it sounds so easy, drop 5 kgs, make my comeback and blitz my PB time.
Sadly I don’t think water running is a good way to get faster or thinner!
Unless you are very big boned I would guess that you any weight loss that came along via training would be amplified as you not only loss X lbs of weight, but also gained Y lbs of muscle which means you lost X + Y lbs of fat.
As long as your muscle gain are in S/B/R useful muscles your improvement should be substantial.
The second IM for me was considerably better as I learned how to manage the run and swim straight, which made for my best overall performance on a much harder course.
Unless you hit your 1st IM perfectly you should be able to drop 30-60 minutes from your time just from base and experience assuming weather is not an issue.
You have so many factors that are changing simultaneously and I think weight is one of the least important.
Although it is individually based, is there any type of common thinking as to when and if weight loss for improving run times affects loss of power on the bike?
Although it is individually based, is there any type of common thinking as to when and if weight loss for improving run times affects loss of power on the bike?
You are always going to be a faster triathlete if you get faster at running, even if you lose a few watts of anaerobic capacity on the bike.
anyway no its not clear when weight loss might cause you to lose power. generally I would say that you won’t appreciably for efforts longer than 20 minutes.
My n=1 experiment this past February -
Last Feb, I ran a PB Half Marathon in 1:34. I am 5’10" and weighed 170 at the time.
This Feb, I ran the same race in 1:40. I am still 5’10" but weighed 180.
I ran slower because I was heavier. I was heavier because I was not training as much. If I had trained more but was still at 180, I would have been a little faster than 1:40. I have had trained more and was closer to 170, I would have been closer to 1:30
I’m way over race weight now after completely half-assing (oxymoron, anyone?) the last couple seasons, but the last year I really trained & raced for real, I definitely reached a weight threshold where I felt like my swimming and bike power began to regress (of course there are so many other overlapping variables it’s hard to precisely quantify apples to apples).
For me, at 6-1, the non-running improvement seemed to flatline at about 172 and get worse below about 170 (at least for flat TTs; of course in the hills the lighter weight still felt like an advantage). However, I’ve never reached a point when losing more weight didn’t seem to still help running (lowest I’ve gotten is 163), although that never felt sustainable as I was continually cold & hungry and hated feeling weak all the time. For IM, the sweet spot was at 167-168, where the gain in running outweighed any slight trade-off in the swim/bike.
As a college runner at 6’3" 165lbs I was running 28:45 for the 8k in cross country (slow!!!). With the same training/mileage, the next season at 150lbs I was running 26:30 simply on weight loss alone. It works for running, that’s a no brainer. Not as simple for swim and bike.
6’3" at 150 lbs…can you say underweight? Seriously…that is just skin and bones dude. I’m 6’3" - 165 lbs and if I lost anymore weight due to training, I would stop.
No kidding…even @ 6’4" 178 my wife said I was looking gaunt and wasn’t allowed to go any lower. I’d still love to race at 175 though.
I know this can be very different from one person to the next but are there any formulas out there to show a general idea of how much speed you can expect to pick up on the bike and run based on a certain amount of weight loss (assuming this is mostly fat loss and not muscle).
I am doing my second IM this year and want to go for a certain time on this one as opposed to “just finish”. I am currently 5’10’’ 180 lbs and about 20% body fat. Currently my max bike is around 21mph for a 20-30mi ride and max run would be around 7:30 - 8:00 Min/Mile for a 5-10k. My goal race weight by the beginning of the summer this year is 170lbs which I haven’t been at since I was 16 years old.
Any ballpark predictions out there on how much dropping 10lbs will increase my speed on the bike and/or run? I realize there are many factors that could go into this. I am not looking for exact #'s, just seeing if anyone else has been in this situation and after dropping some weight, realized a certain amount of increase.
General rule of thumb that I’ve heard is 2-5 seconds/mile per pound lost for running. Some of that (as has been pointed out) will be amplified by consistent training.
FWIW, my n=1: Last year, on two months of fitness at ~ 176 lbs I went 7:30 miles for the first 5k of duathlon nationals. This year, after 12 mos of mostly consistent training and down to 164 lbs @ 5’10" (Thank you 100/100!) I’m hitting sub 7 minute miles in the middle of 10 mile training runs, and had a flat 7:00 pace for 5.5 miles at Ragnar Del Sol this Feb. We’ll see what happens at the Desert Du this weekend.
Well, that depends on the bike course. On a flat course, as you loose weight your power will drop. BUT (and it is a big but), your Power to weight ratio should get better. Meaning you will climb better. So, on a hilly course, your bike times will improve as you loose weight YMMV.
Note, as a fat guy, I get to smoke all you skinny guys heading downhill but as soon as the grade goes the other way you guts are gone. If only the bike courses had a net elevation loss of a few thousand feet and were into a nice headwind, then extra power trumps you guys getting pushed backwards by the wind (not that it is any fun for me but doesn’t affect me as much).