There are at least three tried and tested weight loss diets associated with hiking the world's wild places. I know this because I've tried and tested all three.
(This article was written for publication while we were hiking the Pacific Crest Trail in 2002. More articles at SimonWillis.co.uk)
The first is the Scottish backpacking diet, which, sadly does not work!
Every trip to town requires a visit to the local fish and chip shop, and no matter how little you eat while backpacking over your chosen Munros, a full fish supper or deep fried Mars bar (yes, this artery-attacking delicacy does exist) provides more fat laden calories than you could ever burn off on the hill.
Then there's the trekkers diet, most effectively experienced in Nepal, India, or Pakistan. Weight loss is dramatic and sudden, usually five to eight hours after a local meal.
However, the strain inflicted on the body's purgative systems is a painful drawback.
Now I have found the Holy Grail of the diet industry; a diet which permits you to eat whatever you want, and still the pounds will tumble from your waist, hips and thighs.
Of course, this diet is The Pacific Crest Trail.
For the first time in two decades I could be called "skinny."
I actually startled myself when I caught sight of my reflection in a mirror. I looked like a lollipop, a stick with a ball on top. For a brief moment I fantasized I was developing a six-pack stomach, until Liz explained I was looking at my ribs, not seen so prominently for twenty years.
I have no idea how much weight I've lost because I don't normally weigh myself.
I prefer the simple but accurate weight assessment method recommended by a doctor friend, which he calls "the jiggle test."
Stand naked in front of a mirror and jump. The bits which jiggle, which are not meant to jiggle, are superfluous. Try it. You'll hate it.
Now when I do this test I am alarmed to find my entire skin seems to jiggle! It's as if a layer of fat has been sucked out and my flesh is a size too large for my skeleton.
It's not as if we haven't been eating well. Liz cooked and dehydrated about a third of our vegetarian trail meals at home and these are the ones we relish most.
MSR brand Mountain Gourmet meals come a close second. To everything we add a large dollop of olive oil, injecting a hundred and twenty calories with every tablespoon.
For Liz, this is clearly enough because she looks exactly the same as when we started the trail, a lean but powerful female physique.
For the first two months I experienced no change either, but when we upped the daily distance to between 25-30 and more miles I discovered my engine needed more fuel.
That triggered the phenomenon which long distance hikers call the "trail appetite".
This is a depth of hunger which can never be truly satisfied, as if your legs and arms had been hollowed out to leave more room for food.
PCT hikers have been thrown out of restaurants advertising an "all you can eat buffet" because, like ravenous locusts, they really could eat it all.
I even astonished myself when I put away soup, a large chicken dinner with potato, vegetables and pasta, followed by desert. And then promptly ordered a double cheeseburger with fries.
And if this doesn't sound exceptional to you, then perhaps you too need a diet.