How I determined racing weight/composition:
The proper way to determine racing weight and composition is to test it functionally. You can estimate what it should be (you should do this to get a ballpark figure anyway and I show how I did it for me below), but the only way really to know your optimal weight & composition is to see how you perform. As you drop weight, your performance should increase to a point. Losing further weight will make your performance decrease. That inflection point is your racing weight. That is likely to change with age, tho. I don’t know how easy it is for most age-groupers to generate enough data points to have a reliable picture of optimal weight, however. But I think estimating it will get you most of the way there. Estimating it along with fat percentage will be even better.
There’s the slowman method. It’s on a thread somewhere around here, but basically you are at racing weight when your friends and family stage an intervention.
Looking around the interwebs I found the following info:
http://www.ironman.com/...e.aspx#axzz4h3L8KrtD Optimal BMI is 21. BMI = kg/m height^2. For me at 5’9” = 1.75 m, a BMI of 21 = 64.5 kg = 142.2 lbs.
This link also has a chart with body fat percentages by age. For me, 40-49 male, I’d like to shoot for well-above average which is 10 – 13.7%. Elites are <10%. At 142 lbs, 13.7% is 18.5 fat lbs. I picked 13.7 because it’s the higher end and given my history and body type it would be difficult enough to reach that.
http://www.triathlete.com/...getting-leaner_81493 This site says optimal body fat % is between 6-15% (which largely agrees with the previous site).
https://www.alancouzens.com/blog/height_weight.html This link has a regression between height and weight for Kona pro’s. A select data set, of course, but still useful. Given my height and using the upper confidence limits of the regression, I’d be at approx. 154 lbs.
http://www.racingweight.com/rwe/index.html#/ This is just a straight calculator of racing weight. I don’t know the metrics behind it. According to this site my ideal race weight is 165 pounds & 12.7% boy fat (21 fat lbs).
So what did I do? Picked the middle one. If I get to 155 and have ca. 13% body fat I’ll be happy. When I get there I’ll see how I feel and if I think I should lose more weight and chase 145 or not. I’m guessing not. But maybe I’ll still want to lower my body fat %.
My current weight is 183.6 lbs and body fat is 25.5% (according to a scale, so it’s not the most accurate measurement). So that’s 136.78 lean and 46.82 fat lbs. If I were to get to 155 lbs keeping all of my lean mass, that would be 137 lean and 18 fat lbs or 11.6% body fat. That would be the best I could hope for, I think. I doubt I’ll be able to keep all of the muscle, but I’ll try. Going up to 13% body fat at 155 total lbs is 134.8 lean and 20.2 fat pounds. So that would be a loss of 2 lean pounds and 26 fat pounds. Probably still a stretch, but we’ll see as I get closer.
As I get closer I will try to keep good records of my training to watch out for loss of power on the swim, bike or run. But with all of the other noise in the system like fatigue and other factors, I don’t know if I will be able to tease out the finer details.
Hope that helps.