I'm doing Exante total solution (3 shakes @ 200 cals each)
I'm training a bit differently to the programme they send: 2 short walks and 1 long walk each week.
On the day of the long walk, I multiply the number of miles by 80, to give the approx calories burned. I then give myself a meal, or snacks, of about half the calories I estimate I will use. I have this just before or during the walk. The meal is ketosis-friendly, and then I add in a small piece of fruit. One time, I didn't want to get sidetracked by food, so I had a Slimfast shake. The exercise kept me in ketosis.
At the end of the day, I try to avoid the mindset of "rewarding" the walk with a food-treat. Instead, I try to think of it as "what fuel -if any- will my body need to do this successfully?" At the shorter distances, the shakes were enough. If I need more fuel, what is the best way to get it (psychologically as well as physically)?
Good luck with your training!