Race weight is the weight you naturally come to after doing all of your hard training. Typically you gradually pick up your volume until about a month or two before your goal race with an aggressive taper the last week or two. Because you're doing your most work a 2-6 weeks before the big race, you'll be at your 'race weight' after that big month of training.
Trying to force a 'race weight' early in the build is bad. It should naturally happen due to you doing the training.
With experience one should be able to pin down their best running weight to within a pound. Overextending optimal weight loss will show itself quickly.
Try carrying some 5 pound weights a few weeks on tuns and you will get a stress fracture. Less weight puts less stress on bones.
Me when I know nothing about physiology
Here, let’s both run our ridiculous experiments on eachother, I will run w/ the 10lb weighted vest, you can run on 1000-1200 calories a day, all protein/fat just so you are getting the muscular recovery and making sure your body knows it needs to use your fat (and collagen) as fuel.
Lets both report back in 6 months and see how one another are doing with running and general physical health, and even if we both get stress fractures, we can recover and go back to training/eating as normal, and then I want us to both go in and get a bone health/density analysis in 2 years. I’ll put like 10 bucks on you still having health/injury issues, having an unhealthily low bone density, and hormonal issues, 1.5 years after the experiment while I will be fully functional and still capable of training at a high level.