Pack weight

The suggestion to weigh your food before and after a trip is good.  Even when I choose my menu by just throwing a bunch of stuff on the kitchen table, I still weigh everything and enter it into my packing spreadsheet (OK, I don't really weigh stuff like oatmeal or hot chocolate packs - I usually save time by just going with whatever was in my spreadsheet from last time).  I use a new worksheet in the spreadsheet for each trip, and mark the items I don't eat once I get home.  This makes it much easier to plan longer trips since I can see what worked for previous trips.  Most people I hike with eat less at altitude, and more on low altitude trips.  I've heard that changes if you are out long enough, but I haven't noticed much of a difference between day 2 and day 10 at altitude.  I eat 1.3-1.5 lbs of food a day, and my husband a little less.  Bringing booze or fresh fruits or vegetables ups this weight (and only happens on shorter trips!)

Of course how much you eat on a trip depends more on the calorie content of the food, not its weight.  I shoot for at least 100 calories per ounce for my meals and snacks on longer trips.  Something like oatmeal has less, but after adding nuts and coconut milk or full-fat milk powder it might get up to 100 cal/oz.  Again, I made a master spreadsheet of all my favorite meals and snacks, then read labels and calculated the calories per oz for each item.  Nuts are really good, around 160 cal/oz.  They also pack small in a bear canister so I bring a lot of them.  Cheese varies with the variety with some of the hard cheeses being at least 100 cal/oz, but something like a soft Laughing Cow cheese is less.  Lately we have made cheese crisps, adding some nice crunch and increasing the cal/oz by cooking out excess water.  Beef jerkey is surprisingly low, with fatty hard salami being higher.  Sugary stuff like jelly beans or gatorade powder is in the middle.  In the end the trick is to find a variety of lightweight, packable stuff you will enjoy eating.