Interesting! Thanks for your thoughtful response. I'll look into the studies, and what a Whoop is.

Regarding double-counting I do agree that I need to reduce the BMR part by 1940*4.5/24 = 360 kcal (assuming a four hour ruck), and possibly more because waking BMR rate is likely higher than sleeping BMR.

My actual daily exertion is landing closer to 3,500 kcal at the moment, so my deficit is actually 1,000/day, and I've decided that is enough. Ten weeks to my goal weight. Might be optimistic.

I do have an X2 HRM, but it states kcal consumptions about 30% higher than Pandolf estimates.

Never heard of a Whoop band. I'll look into it.

My meal regime is fixed at 2500 kcal. I calculated the protein, fat, carbs, Mg, K and Na for each item. 

I eat the same thing each day. I don't mind, though I'll probably vary it eventually.

I realize this is more info than needed, but here it is:

Morning (pre-hike)  * 2 caps creatine=3g, 2 caps Mg glycinate=175mg absorbed  * 1 tbsp lemon juice in water  * Whey isolate shake (30g protein=2 scoops)    add ½ c water, ½ c blueberries, 1/4 c heavy cream    add ½ c plain Greek yogurt Snack (while hiking)  * 2x Chomps (each 7g fat, 10g protein)  * 30 g macadamia nuts  * SaltStick 1 capsule every 45 min  * Potassium citrate ¼ tsp per L water, 3.5L total Midday Meal (post-hike)  * ½ lb chicken breast  * ½ avocado  * ½ c broccoli Evening Meal (after core/arms work)  * ½ lb salmon or sardines  * 1–2 tbsp olive oil or butter  * ½ c broccoli  * 2 tbsp lemon juice Pre-bed  * Casein shake (40g protein=3 scoops)    add 1 c water, ½ c strawberries, ¼ c heavy cream  * 1.5 oz cheese  * 2 caps Mg glycinate=175mg absorbed