Weight plays an important part in running performance. The heavier you are, the higher is the energy cost of running at any given pace.
I know I perform best when I am near the bottom of my healthy weight range, crucially – not too light! You won’t run well if you’re undernourished or if you don’t have enough body fat to support basic health.
Remember just because you’re at your ideal weight it isn’t a guarantee of successful racing. Fitness of course plays a key role here, but assuming you’re fit, you will generally have your best races when you’re about as light as you can be without compromising your health. This is the balance professional cyclists are always fighting for.
Your ideal racing weight is determined primarily by your body fat level. There’s not much you can do about the other sources of mass in your body: bone, muscle, water, etc. No matter how hard you train or how carefully you eat, all of that weight will stay. It’s excess body fat that accounts for the difference between current weight and ideal racing weight in most runners, and thus it’s fat mass that you must lose to attain your ideal racing weight.
So, what is your ideal racing weight? Given the fact that body fat is the primary determinant of ideal racing weight, the best way to estimate it is to calculate how much you will weigh when you’ve reduced your body fat percentage to the optimal level. Optimal body fat percentage is not the same for everyone. There are many factors that affect how lean an individual runner can become. These include gender, age, genetics, and history of being overweight. However, even runners who have all of these factors working against them can get fairly lean.
You can expect to reach the lower limit of your ideal range only if you typically lose weight fairly easily, you have never been seriously overweight, and you are willing and able to maintain a high training volume. If your current body fat percentage is well above your optimal range, you should aim only to reach the upper limit of that range initially through increased training and improvements in diet.
Estimating the body fat percentage you can realistically expect to attain at your peak fitness level is not an exact science. Just use common sense and the considerations to make an educated guess for yourself. Also bear in mind that the further you are from your peak fitness level currently and the more room for improvement your diet has, the more you can expect to lower your body fat percentage.
It’s also perfectly normal to put weight on and healthy after major racing goals so don’t let this worry you. Obviously don’t go over board but once you get back in to training post event you can expect the weight to once again lower as you build back up to your next key race(s).
