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-- published in the July-August 2004 issue of the Appalachian Trailway News --

Why Hikers Get Fat:

The dirty little secret of long-distance hiking

By Charlie Duane

When I thru-hiked the Appalachian Trail on the occasion of my fiftieth birthday in 2001, I hoped to receive the gift of physical health. The Trail granted my wish, helping me get in the best shape of my life. My post-hike adjustment, however, failed miserably - at least from the standpoint of sustaining the same health benefits at home.

Some of the post-hike problems were simple: I did not know how to perform stretching exercises, so painful muscle tightness immobilized me. But, more troubling was the inability to "downshift" my metabolism without exercise: my weight increased by a half-pound per day for weeks. It seemed that the same foods I ate before hiking the Trail made me heavy. I went from an athletic 142 pounds to an overweight 173 pounds in five months. Trustworthy friends called me "fat."

It wasn't just me. At hiker reunions, I expected to see bodies like those of marathoners or competitive cyclists, the bodies we had all developed while thru-hiking. Yet most hikers older than age 40 looked dumpy, like me. Veteran hikers offered limited help. "Avoid french fries," or "Cut your intake," they advised. As much as I wanted to listen to them, I was listening to my body too, and it said I was hungry!

Authors seemed to have no answer either. A Pacific Crest Trail expert advocated the "raw food diet" on his Web site, but abandoned his next distance hike due to weakness. An oft-published writer fielded my e-mail inquiry about weight gain this way: "That is one question I wish I could answer. I think [thru-hiking] has wrecked my metabolism."

Without a coherent nutrition strategy, the only solution for reducing my weight seemed to lie in "upping" my exercise level. So I planned another long hike from Baxter State Park, ME to Cap Gaspé, QC. As soon as my legs loosened up, I trained for six miles daily with a pack, and set out to hike. I never even made it to the summit of Mt. Katahdin. Everything backfired. I felt so lousy that I quit on the first day, then fell ill for two weeks. Apparently, being overweight was not my only problem.

I returned home in a curious state of shock, denial, and perplexity. A year earlier I had attained the build of an elite athlete, averaging 22 miles per day on mountain trails, completing the A.T. thru-hike in 97 days. Now I felt like an aging boxer, getting knocked out at the opening bell of the first round, not knowing what had hit me.

I did not stumble. I fell. Hard. Was this the dirty little secret of long-distance hiking, falling out of shape off the Trail?

Weight gain was not just an academic question for me. My doctor had been recommending medication to lower my cholesterol for years, but gave me a reprieve to work things out on my own. In fact, hiking all day on the Appalachian Trail represented a way to raise my activity level in order to improve cholesterol test results. Since my grandfather died of a heart attack at the age of 47, heart disease has always been a personal concern. These concerns heightened for my age group last summer when two friends, whose kids had joined mine in play groups, died of heart attacks within a month of each other.

My aborted hike turned out to be a blessing in disguise. A month after quitting, I walked into a bookstore and bought a stack of health books. Better informed, I resumed and completed my hike into Canada. It took a year of searching but I finally rediscovered the gift of health that I had experienced on the Appalachian Trail. I found it in what I call "Balanced Nutrition".

The words you read here were mostly composed during my southern roadwalk (Springer Mountain, GA to Key West, FL) in January, 2004. During that time, I averaged 28 miles per day and walked 50 miles on the final day, to cap off my hike of the entire East Coast in three sections. My weight and physical form have subsequently been fine. In fact, I ran a half-marathon in my trail shoes on a dare.

Without any medical background, I'm trying to say in hiker jargon, what my grandfather and friends needed to hear long ago: you can improve your health, as well as your weight, with balanced nutrition.

Hiking in the Zone

Interestingly, the first clue to getting back my health came from The Complete Walker IV, by Colin Fletcher. Fletcher is well known to hikers. He wrote The Man Who Walked Through Time, which documents the first continuous walk through the Grand Canyon carrying a massive backpack, and which has inspired many of us. At first, I doubted his comments on nutrition, since I practice a much more "lightweight" hiking style.

Fletcher writes that despite his high level of activity, he developed heart disease requiring bypass surgery. During his recuperation, he discovered The Zone, published in 1995 by biochemist Barry Sears. This popular health book provides a system for getting a balance of nutrients in your meals. Fletcher lost about 30 pounds of excess weight on the nutrition plan, found he needed less sleep, and still goes in for the Zone "in a big way."

I had managed to lose 6 or 7 pounds by skipping one meal daily for a couple weeks before reading The Zone. In the next two weeks, I surprisingly lost the same amount of weight, eating three square meals a day plus snacks. (Eating all I wanted certainly rated higher than starving myself.) But the best news came from a cholesterol test at the end of those two weeks. Even though my attempts at the new eating plan could be called haphazard at best, my first optimal results in 15 years came back! Reading the report with tears in my eyes, I, too, climbed aboard "in a big way."

Of all the health books I have read, the inexpensive paperback A Week in the Zone may be easiest to follow. It summarizes the other Zone books and shows how to balance "food blocks". For my friends who find it too complicated, I have composed three guidelines, which I give them on a business card:

1) Eat some low-fat protein such as white meat, fish, or soy.
2) Choose plenty of vegetables and fruit for the carbohydrate portion. Highly refined carbohydrates such as flour and sugar should represent only ten percent of total intake.
3) Include some healthy fat, such as olive oil or nuts.

In practical terms, a Zone-balanced snack could consist of an ounce of meat accompanied by a cup of vegetables (or a half-piece of fruit) and a few nuts. A meal could consist of a handful of protein food accompanied by two cups of vegetables, a piece of fruit, and a dozen nuts. For distance hiking, you would increase the amount of nuts.

When you hike all day for more than two weeks, you probably seek out "quick energy" foods, anything to pack in the calories. But when you return to "inactive" life at home, the quantity of your exercise reduces by ten times, and so should your consumption of of those calorie-dense foods. Keep that in mind when scanning the list below.

Starches, sugars, and animal fats must be cut back when you exercise less. By starches, I mean potatoes, French fries, chips, bread, pretzels, crackers, cookies, donuts, rice, and pasta. By sugars, I mean soda, sports drinks, candy, chocolate, ketchup, convenience snack foods, and many "sports bars." By animal fats, I mean fats found in meat trimmings, bacon, sausage, hot dogs, fast-food hamburgers, whole milk, cheese, butter, ice cream, and egg yolks.

You need not eliminate these foods, I've learned, but you should minimize them. Do, however, eliminate any foods made with hydrogenated oils, the wicked cousin of animal fats. Hydrogenated oils find their way into some deep-fried foods like fries, chips, donuts, many convenience foods, cookies and some breads. Pass up foods containing hydrogenated oils when you see them listed on the ingredients label.

You can replace the dangerous foods with plenty of vegetables and fruits, along with modest quantities of nuts. In exchange, you will store valuable disease-fighting micronutrients in your body.

Okay, that's my quick answer to why hikers get fat and how they can adjust the balance of foods to maintain their hiking form off the Trail. Here's some of the logic and theory behind it all.

Implications of the Glycemic Index

Understanding carbohydrates in terms of the "Glycemic Index" can help you get a handle on the problem. The Glycemic Index, easily found on the Internet, was developed in the early 1980's by Professors David Jenkins and Tom Wolever at the University of Toronto, as a way of showing how much a particular food will raise your blood-sugar level.

For example, a banana will raise your blood sugar level faster than an apple, and a soda will raise it even faster. But broccoli and cauliflower hardly raise your blood sugar at all. Protein and fat don't ordinarily raise your blood sugar, so you will find mainly carbohydrates on the Glycemic Index.

Generally speaking, starches and sugars rate higher on the index while vegetables and fruits reside lower on the list. This is because grains found in breads and pastas have been thoroughly milled, becoming quickly digestible in the process. Sugar and corn syrup have had all of nature's "external packaging" removed, leaving you with a dense concentrate. Meanwhile, broccoli, tomatoes, peppers, and apples retain all of their natural fiber, which slow the process of digestion and provide a longer-lasting supply of glucose (sugar) to the bloodstream.

You can see how this works by comparing the proverbial apples and oranges. When you compare oranges to orange juice and apples to apple juice, you discover that in both cases the whole fruit is lower on the index; the juice is higher because it contains little or no fiber.

High-index foods tend to raise blood sugar rapidly and burn off quickly, while low-index foods raise blood sugar gradually and burn off slowly. Teenagers and young adults often have better tolerance for quantities of high-index carbohydrates found in sodas, candy, and snack bars, but those of us over forty often respond by gaining weight.

Many people induce high and low blood sugar in themselves by consuming too many foods ranking high on the index. When they sense an oncoming blood-sugar crash (combining hunger with feeling dull), they may turn to caffeine, tobacco, or other stimulants to jump-start themselves. Or they may turn to even more high-index foods, causing elevated blood sugar and elevated insulin levels all day.

The GI has been useful to help diabetics gauge the glycemic load of meals, adjust their insulin injections, and so maintain steady blood sugar levels. Athletes and ordinary people find the GI useful in choosing foods providing a balance of durable versus quick energy.

Putting your diet to the test

Try purchasing a portable glucometer and finger-prick kit at your local pharmacy (which may run $25 to $40, including the test strips). These kits, usually sold to diabetics, demonstrate how dramatically blood sugar can fluctuate.

Eat a couple pieces of toast with jelly, drink a glass of orange jucie, and test your blood sugar 45 to 60 minutes later. You may be surprised at the spike in your blood sugar levels. If your blood sugar starts at 85 mg/dl and rises above 140 mg/dl, then it has begun to yo-yo. Next, you should perform the same test after eating some lower glycemic foods, such as an apple and an orange.

Running this kind of information by a physician might get you diagnosed as "hypoglycemic" or "pre-diabetic." But, I prefer to think of the distance hiker's metabolism as a gift with a catch. To maintain your form, you must eat almost exclusively healthy foods. If you learn what these are, you'll be around for a long time.

By performing blood sugar tests, I have found my metabolism to be "carb-sensitive." High glycemic carbs raise my blood sugar quickly. It's the reverse of my youth, when I could eat anything. But my metabolism gradually changed in middle age, and I think the thru-hike pushed me all the way over to carb sensitivity.

The standard cholesterol test provides clues to how well your metabolism has been "burning" its fuel. The following summaries point out the relationship between your food, your overall score and the individual components.

Your total cholesterol count (TC) can score 200 or below when you choose the right foods for your body. If your total cholesterol hovers around 250 or more, you may want to find fuels that your body burns cleanly. One option is to go back to exercising twelve hours per day. The other option is to adjust your fuel mixture.

Triglycerides (TG) basically reflect blood sugar levels, which lead to the formation of blood fats. Think of cattle being penned and fattened for market; they are fed lots of carbs in the form of grain. People leading sedentary lives and consuming pastries will likely produce high TG levels. A TG score of 30 is fantastic, 60 is good, and above 100 reflects elevated blood sugar levels. Consume plenty of fibrous vegetables to reduce TG.

High-density lipoproteins (HDL) reflect the amount of cholesterol that your blood carries away from tissues, like traffic leaving a city. Exercising for an hour each day, even simply walking, helps keep HDL at healthy levels. Physical activity increases circulation, causing your blood does more of its normal work. You want to keep this score high, preferably above 50 or 60.

Low-density lipoproteins (LDL) usually get named the bad guys, but actually only excessive levels present a danger. These lipoproteins carry necessary quantities of cholesterol to the tissues, like traffic entering a city. However, too much LDL is associated with waxy deposits in the arteries. You should aim for LDL of 130 or less. Animal fats raise LDL; broccoli, lentils, and oatmeal lower it.

Kenneth Cooper's 1988 book, "Controlling Cholesterol," supplies the following useful information:

TC = (TG / 5) + HDL + LDL    [he actually had it: LDL = TC - HDL - (TG / 5)]

For non-scientists, that translates as follows: "Your total cholesterol equals one-fifth of your triglycerides plus your high-density lipoproteins plus your low-density lipoproteins." Plug your scores into the formula, reference the summaries above, and modify your diet accordingly. This formula reveals that you must work aggressively at reducing TG to double digits, and lowering LDL.

A second useful formula gauges your insulin status from two components of the cholesterol test, according to various Zone books by Barry Sears:

TG / HDL < 2

That translates as follows: "The product of your triglyceride divided by your high-densisty lipoprotein number should be 2 or lower." Less than 2 indicates desirably low insulin production, the lower the better. Greater than 2 suggests risk of inflammatory conditions in the long run, such as arthritis, diabetes, or heart ailments.

Theory of the insulin-sensitive hiker

In my opinion, the calorie-deprived hiker becomes more carbohydrate-sensitive and insulin-sensitive over months of continuous exercise. The hiker's metabolism reverts to ancestral traits.

Carb sensitivity emerges during a thru-hike because the body can only store limited amounts of sugar, to be used for sprinting or a "hard push." In quickly depleting those reserves each day, and in restoring them with sugary snacks, the body develops a hair-trigger response to the stimulus of food.

Here's where the off-trail trouble begins. The same snacking habits that work on the Trail, cause constantly elevated blood-sugar levels off the Trail, inducing the body to produce excess amounts of insulin. Most people respond to overproduction of insulin by growing fat. They, and some who remain thin, face additional risks: bombing the body with too much insulin usually causes the body to become less responsive over time.

Gerald Reaven calls this subject "insulin resistance" and describes its signs in Syndrome X, The Silent Killer. His prescription for completely preventing or overcoming this problem includes eating healthy fats, and exercise.

While "insulin resistance" involves the overproduction of insulin, "insulin sensitivity" occupies a healthier place at the opposite end of the spectrum. How does the thru-hiker typically arrive there? By lots of exercise during the thru-hike.

S. Boyd Eaton writes in The Paleolithic Prescription, "Physical endurance training increases the sensitivity of the body's cells to insulin. Studies show that the physically fit secrete less insulin after being given test doses of carbohydrates than do the physically unfit."

Most experts discussing the effect of exercise on the metabolism refer to one or two hours of exercise per day, and even the elite athletes recommend days off. Bill Pearl's Getting Stronger, The Lance Armstrong Performance Program, and Dave Scott's Triathalon Training all recommend rest as a vital component of physical conditioning.

Nobody, but nobody, has described what each year's class of A.T. Thru-hikers do to their metabolisms 10-12 hours per day, often 7 days per week, for months on end. An excerpt from Barry Sears' Age-Free Zone offers some insight into the cumulative effect of all this exercise. "... actively exercising muscles take up nearly 30 times more glucose than they do when they are at rest. This uptake of blood glucose is a noninsulin-driven event, and to this day [1999] it is not well-understood exactly how this process takes place."

I submit that, under thru-hiking conditions, muscle action converts a great deal of blood sugar to energy, so that the body's insulin requirements stay low and remain low for a remarkably long time. A before-and-after study would probably show that thru-hikers' insulin levels drop to half of initial levels or even less. The most significant measurements ought to come from those at the end of their thru-hike, taking the fewest zero days.

Most of us have been raised in an environment that builds tolerance for high sugar and flour content in food. However, insulin sensitivity developed by thru-hiking removes that tolerance, making the hiker's biochemistry behave like a paleolithic nomad. So the thru-hiker experiences the same difficulty with the "modern" diet that primitives and retired athletes do.

To accommodate this new-found insulin sensitivity, off-trail distance hikers may find inspiration in hunter-gatherer diets, or in any plan that uses the modern food supply to produce similar benefits. See Ronald F. Schmid's Traditional Foods Are Your Best Medicine for background on whole and refined foods.

At a health level, choosing vegetables and fruits for carbohydrates comes down to much more than skipping "empty calories" to control weight. According to Kilmer McCully in The Heart Revolution, consuming fresh, whole foods prevents long-term vitamin B deficiencies at the root of arteriosclerosis.

Down the trail

Medical authorities have conflicting views about what foods are healthy. As S. Boyd Eaton observes in The Paleolithic Prescription: "It is often difficult to feel confident about which health advice to follow... The debate that results is often acrimonious... This may confuse us, but it pales beside the confusion wrought when respected authorities within mainstream medicine disagree among themselves."

I say, let the experts measure the amount of refined foods consumed in their nutritional sudies. The dietary "rules" might be much different for us if we consumed only fresh, whole foods. But since refined foods have come to stay, we must balance their nutrition as best we can.

Meanwhile, newspapers and magazines routinely run sobering stories about the extent of weight problems experienced by the general population, and, coincidently, similar numbers for chronic diseases: 65 percent of the U.S. population. The burden of these problems falls on each of us in the form of oppressive medical costs or health insurance premiums. Balanced nutrition can reverse these costs, without turning everybody into a full-time thru-hiker.