website or program?

Diane, that is a tough one. There are too many variables. There is a huge amount of variation in what some people call dehydrated.

You can weigh the dry food, and then you can take a very rough estimate of 100 calories for carbohydrates and more for fats.

–B.G.–

I use Excel to calculate my food value and weights, you need to start weighing and putting the results into the spreadsheet, over time you'll build up a bank of data of all the foods you like. I can put together a days food in a flash due to my spreadsheet but then I can eat the same foods on multi-day trips and look forward to the same thing so you really need to work out what you like eating.

I normally allow 3000 calories per day but on my next trip of five days, I'll be taking 2600 calories, it'll be interesting to see how I manage, I might burn some from the waist but it's not going to be an overly strenuous walk.

This information may help.

Food calories per ounce.
http://web.archive.org/web/20050305231402/http://www.oc.edu/staff/phil.heffington/FoodCalories.htm

Calories used while hiking.
http://web.archive.org/web/20041214163422/http://www.oc.edu/staff/phil.heffington/BackpackingCaloriesII.htm

^^^^

The "BackpackingCalories" link above leads to this table –

– which in my experience, is highly dubious as a guideline of utilization, let alone for intake. (And makes no allowance for climbs and descents.)

A total weight of 175# leads to 5565 calories over 10 hours. 550 calories per hour of output is pretty hard to sustain over the course of a day. Given that most people can only eat and process about 300 calories per hour, the deficit would lead to a weight loss of almost .70 pounds per day.

Using the JMT FKT effort as a guideline we see that Andrew Bentz's recent record was set on 200 calories per hour, and Ralph Burgess' consumption rate was about 290 calories per hour.

Cronometer (online and app versions) will let you build up a recipe out of ingredients, and it’s got the full USDA database as well as quite a few other things included. What I do for homemade dehydrated stuff is create a recipe from the “before” state (fully hydrated) and figure out calories/serving from that. Then I can weigh a serving of the “after” state, and assuming that all the lost weight is water it’s reasonably accurate to figure out where it stands on all major nutrients.

I'll add to your question since I don't know – if I dehydrate something, does it change the calories/nutritional profile for that food?

Yes, I know they seem high, but it's not uncommon to see those numbers, it's a guide and something to think about.

The text below was lifted from the Nutristrategy site.

Energy expended or calories burned during exercise is influenced by body weight, workout intensity, conditioning level and metabolism. The chart shown calculates calories burned per hour for different body weights.

http://www.nutristrategy.com/activitylist.htm

Did Andrew Bentz's and Ralph Burgess consume those calories per hour plus the 2000 calorie daily allowance.

"Yes, I know they seem high, but it's not uncommon to see those numbers…"

Unfortunately.

Elite Tour de France cyclists can manage about 350 calories per hour while riding. The remainder are consumed while off the bike.

"Did Andrew Bentz's and Ralph Burgess consume those calories per hour plus the 2000 calorie daily allowance."

Andrew didn't mention an "evening meal". Ralph's numbers are all-inclusive.

If you exercise it can affect your base metabolism how many calories are consumed the rest of the day

If it's colder you'll burn more calories

Different people utilize the food more or less efficiently. Many of the calories exit the body unused

For a few days, your body will supply calories

Maybe better to just use experience of yourself and others how many calories they need per day

Does not change it's calorie content. If you know it's caloric content when hydrated, you'll know it's caloric content when dehydrated. :)

Late to the party, and most questions answered, but people may be interested in some additional reference points wrt calorie expenditure. It's really hard to know what to make of a table of calorie expenditures that makes no allowance for velocity or terrain (perhaps there was at least some additional info on the original version of the table), but those numbers seem at least a little high relative to my own estimates of expenditure per hour hiking when averaging ~ 2-2.5 mph over typical Sierra and Rockies trail terrain. The data the table summarizes presumably are based on a more brisk pace.

An interesting reference that looks at calorie expenditure under relevant conditions is a paper entitled "Energy Balance during Backpacking" by Hill, Swain and Hill in the journal Physiology and Biochemistry. It's available online. The three subjects burned about 3500 calories/day on ~ 20 mile days at a pace similar to my 2-2.5 mph. It's worth noting that there was a lot of variation among the subjects. Given that, it's anyone's guess what the average would be within a larger population, but unless that variation is atypical, it's also a good reminder that even the most accurate table of average energy expenditure relative to time or distance on the trail probably isn't going to tell you your own expenditure with any real precision. (One might therefore wonder whether it's worth trying to get too precise about trying to figure out how many calories to bring based on expected expenditure.)

The subjects in Hill, Swain and Hill took in far fewer calories than their daily gross expenditures of ~ 5000 calories/day, and displayed the expected loss of weight, but IMO it's quite clear this was by choice, not as a result of their bodies' inability to process larger amounts of calories. In my experience, it is not at all difficult to take in well over 5000 calories/day without any special efforts, such as consuming special supplements while hiking or pushing the limits of what can be eaten after the hiking is done. At modest exertion levels such as those described, I have never experienced limitations on my ability to process regular food while walking. (This is in stark contrast to what happens at high exertion levels such as would be experienced during running or competitive cycling.)

For any of a variety of reasons, I and many others have of course comfortably backpacked while in caloric deficit on the order of 2000 calories/day, at least for a few days. It is a virtual certainty that Bentz, Burgess, and anyone else setting trail records over distances that can be covered in a few days are doing so in significant caloric deficit. For the JMT in 3-4 days, a quick thumbnail calculation suggests a gross expenditure on the order of 40,000-50,000 calories. It would be really, really hard to take in anywhere near that many calories.