Control weight while preparing for triathlons

Question

I have a BMI of approximately 25 (87kg, 1.87m), which is just about where I want to be (I look too skinny if I'm lighter).

As this is the weight I've been for quite some time, I consider this to be OK for a relatively flat Ironman 70.3 race. Obviously, I'm not trying to win it, my goal is 5:30 for that one.

However, I have an extremely hilly Ironman 70.3 race one month later (2600 m elevation on the bike leg, and 1100 m elevation on the run). In order to get an OK time there, I would need to lose some weight, maybe as much as 5 kg. The power to weight ratio is obviously quite important here. (If I can finish at around 8 hours on this one I'm super happy).

How should I proceed, in order to get the best possible results on both? I would prefer to keep my weight until the first race, but I'm not sure that's a good idea. I guess I would lose a lot of muscle mass in my legs and thighs if I lose more than 3 kilos in only one month?

Any suggestions / help would be greatly appreciated!

Answer 1

First off, on a hilly ride, the time saved from being lighter is roughly proportional to your weight + bike weight. Assuming your bike weighs 8 kg, that puts your total weight at 95 kg. Cutting 5 kg saves you only about 5% of your time. The effect will be less for the run.

If you want to lose some of your muscle, you're in luck; there's nothing like long-distance endurance exercise to tear the muscle off of you. If you tip the balance to being calorie-negative, you will lose weight - some muscle, some fat.

However... you are probably also going to be compromising your training and your recovery. Trying to both improve your condition and reduce your weight is very challenging.

If I wanted to do this, I would try to cut the weight of early and then be in a weight maintenance mode in the time leading up to the second race.