Caroline, a couple of things here. First, you say you can prevent or diminish addictive desire by reducing sugars and keeping insulin levels steady without peaks and troughs. That’s only part of the story and will only take you so far. Remember (for example) you had a desire for ice cream when your family were all eating some? I’m not saying eat or don’t eat ice cream, but that wasn’t due to insulin levels!
As for the walk, you have a couple of weeks to go and are no doubt doing some walking now to prepare. So maybe take this opportunity to experiment with different foods? There’s a lot of evidence now that athletes improve their performance on low-carb-high-fat but they would be good at fat-burning instead of glucose-burning for fuel. Your sustained energy up and down that mountain will depend on your own metabolic flexibility; your body’s ability to burn fat for energy as well as glucose.
This site – https://nutrita.app/ – may be worth a look as it has both nutrient density rating and insulin index. My take on it is that nutrient density would be just as important for your climb than insulin release, and maybe more so.
I hope this is helpful!