When I do meal planning for extended backcountry work trips, I budget at 4,500 calories per day per person. For backpacking trip it can be less but by how much is higly variable and depends upon your load, terrain, and speed. I'd say the 3,000 is quite conservative. For 2 to 3 days, almost any diet will do but extended periods there has to be some realisitic planning.
I've only known one person to gain weight on a work trip at 4,500 planned level and she was a marathon runner with very low body fat. I don't know if her body fat increased but she had noticable increase in muscle development at the end to 2 weeks. She was also eating more than the 4,500. Breakfast oatmeal became triple servings then doubled again then with raisins then added honey then added Reese's pieces then added butter. I'm not sure what would have happened if we stayed another week.
People should do their own shopping, I just give the guidelines on how much to take and what kinds. The basics are 2 oz of meat, 2 pieces of fruit and 1.5 bagles per person per day. I usually throw in a couple of lbs of chocolate candy and 6lbs of pretzels. Ignore the serving size on the container and go by weight After that it's pretty much what you want with 100 cal/oz for everything except fats and sugar which are 200 cal/oz. More detailed calculations are pointless. The intent is to keep the diet as close to normal as possible and fill out the calorie requirements with snacks. At the elevated calorie levels, there is a problem with the stomach being unable to hold the mass in only 3 meals without drastic changes in food composition. The extra calories are delivered between meals.
I have been on the receiving end of someone else's mandantory "good" diet several times and it is not pleasant. A two week work trip in the backcountry is not the place to be enforcing your idea of what is good for someone else. If you are ever tempted to enforce dietary ideals, remember you are isolated and outnumbered by people with implements of destruction.
People will tend to eat more fat but I try to make it available rather than plan it into meals. After a week, I see people eyeing the squeezable butter and wondering if they can chug it. I've also seen contests to determine who can eat the most Reese's cups in one sitting. It was a tie when we ran out, then we started dinner preparations.
Several years ago I had one person who was a fanatic about calorie intake and diet. He maintained his food list for about 4 days. Then one night around 1AM he got out of his tent, dropped the food bags and pigged out. After that he was much better to be around.
The one item on the backcountry work trips is that the Forest Service
usually provides pack animals for tools and food, you carry personal gear.
However I have been on trips where we had to carry everything and a couple
of people came in with us for a day trip to ferry supplies.