A recent thread discussed calories in food and whether one could eat enough on the trail to make up for calories expended by exercising. One poster stated that he could not choke down enough food per day to maintain a constant body weight. I have the same problem; I don’t seem to be hungry enough to replace calories burned during a days hiking.

One point that seemed clear to me was that it is difficult to reliably estimate how many calories one burns during a day of backpacking. There are conflicting sources of information. I have seen estimates of calorie expenditure ranging from 3000 to over 6000 calories per day.

One web site I found http://www.nutribase.com/exercala.htm lists calorie consumption per 30 minutes by activity. Using this site, I have come up with some incredible numbers. For example the table gives the calorie consumption for a 175 lb man carrying a 30 lb pack as being about 820 calories per hour. For ten hours, this individual would theoretically burn in excess of 8200 calories. Adding in basal metabolism and maintenance requirements would increase this to around 9000 calories per day. At roughly 115 calories per ounce of food carried, this person would need to carry nearly five pounds of food per day to maintain weight. Personally, I do not place too much faith in this particular web site.

I did find a web site that seems to provide a reasonable estimate of an individuals daily requirements based on hours of various levels of activity. Go to http://www.exrx.net/Calculators/CalRequire.html and review the calculation procedure. You need to estimate the number of hours of activity in each of several intensity categories, fill in the gender, size, and age information and the site will calculate an estimate of each day’s calorie requirements.

For me, a male, 5’ 10” in height, weighing 175 pounds, in my early 70s and hiking for ten hours a day at a moderate pace, the estimate rounds to about 4000 cal/day. I normally carry about 1.5 lb of food per day at about 110 calories per ounce or about 2650 calories per day. This means that I hike with a calorie deficit of 1350 calories per day and should loose about 0.4 lb per day or four pounds every ten days. This agrees closely with my “on the ground” experience.

Most backpacking food will contain somewhere around 110 calories per ounce. So, without needing a detailed spreadsheet analysis you can come up with a reasonably accurate estimate of how many calories you are carrying per day. Of course if your diet is mainly butter with an olive oil chaser <img src="/forums/images/graemlins/tongue.gif" alt="" />, or you simply love rice cakes, you will need to revise things. Using the 110 calorie per ounce figure together with the daily calorie estimate from the http://www.exrx.net/Calculators/CalRequire.html site should let you know where you are on the weight gain/loss spectrum.