Wanted to add to that topic since I have some experience on the subject.
Specifically, I want to address -
- Stated requirement of 3000 calories a day
- Switching from a modern diet to a more agrarian/paleo diet
- Real-world calorie deprivation effects on performance
As opinions on the subject are plentiful and often not based on reality I will limit my commentary to what I have experienced firsthand.
I spent a ~90 day rotation in an operational setting living on a very carefully measured 1200 calories a day. I slept 7-8 hours a night, worked out ~3 hours a day, conducted range/tactical training everyday and conducted my assigned duties as well. This was in a very high altitude mountain environment. I began at a fit 210 pounds. The first two weeks were a bit difficult to adjust to, but after that it was smooth sailing. Regarding workouts, I managed to not lose any strength, but made no appreciable gains in strength. At the end of that 90 day period I was VERY lean as I had lost about 25+ pounds. While I lost a lot of fat, I also lost some muscle, but was able to perform all my duties without any real difficulty.
On an earlier deployment, we spent a few months conducting reconnaissance patrols which meant living of of stripped down MRE's. While MRE's are designed to be calorie dense, they create a special kind of havoc in your GI tract. I recall augmenting our diet with local fruits whenever we could, which was a real morale boost if nothing else. I remember a colleague of mine talking about his time in Recondo school "back in the day". He had gone days without eating when he was able to kill a tiny snake and roast it up for chow. He described the energizing and moralizing effects of the hors d'oeuvre size meal as "incredible".
I would also note that when I am conducting my classes I rarely eat during the course of the day. It's not necessarily intentional, it just happens as I am so busy with the COI. Usually wrapping up at the 12th hour of an 8 hour training day, my stomach will make it's demands known.
Lesson learned: I can effectively operate for at least 90 days on a calorie deficient diet. (It should be noted that environmental conditions were moderate to poor. Extreme conditions would have made an impact on the outcome.)
Another time I decided to check the effects of sustained zero caloric intake. I went 7 days with no calories, just water. I still worked and worked out (for the first few days).
Day 1 and 2, I felt fine physically and was able to workout normally. Mentally, I found myself thinking of food more and more. Day 3 was awful. My energy levels crashed substantially, my morale plummeted and my workout was fairly pathetic. Day 4 I kind of levelled out a bit. I found I had to sleep more and my workouts ceased as I simply did not have the energy to both workout and do my job. Days 5-7 I seemed to reach some equilibrium. My energy levels were low, but I was functional. I had increased my sleep to around 10 hours. I thought about food constantly, but it wasn't as distracting as it was earlier in the week. I lost close to 15 pounds over the week, but gained it back quickly when normal eating resumed.
Lesson learned: I know I can go a full week with no eating and still perform at an acceptable (but miserable) level. Bear in mind, I was not dealing with particularly harsh weather or sleeping in the wild, as these factors would also contribute unfavourably to your situation and would need to be accounted for.
Another factor to bring up is our bodies' ability to make the shift from the modern western diet to the agrarian/paleo style diet. This will of course vary wildly based on your current eating habits. I'm sorry to say, but if you eat a rather typical American diet, you are going to have a rather uncomfortable, if not crippling transition to make. The smart move is to begin that transition slowly right now. Start by cutting down on "boxed", processed and sugar laden foods. Eat more raw fruits and vegetables instead of cooked to help adjust enzyme production. Eat less canned products and baked goods. Try to remove white, processed sugar from your diet entirely. Instead satiate your sweet tooth with fruits. Branch out and try eating less common and more organic meats, like bison, rabbit, quail, lamb, local fish and organic pork. This will help "adjust" your system as well as condition your palette to more "gamey" flavors. I remember eating goat for the first time overseas, it was difficult to get down due to the overpowering gamey taste. Another trip I had horse ka-bobs and I have to say, not too bad at all.....just say'in.
The last point I would bring up, which is a touch off topic but bears mentioning is, oral hygiene. How many of you have made provisions for the future care of your teeth? Some people are blessed with a higher oral pH and a genetic disposition towards an oral environment unfriendly to destructive bacteria and acids, but they are in the minority. Having tooth care products such as brushes, floss, xylitol and an emergency filling kit + extraction tools can have a significant impact on your future quality of life.
Might look into the book "The Great Starvation Experiment" for some interesting data. It covers Ancel Keys' experiments on 36 volunteers near the end of WWII.