Beware the "Bonk"

There’s nothing worse than crashing partway through a life-list hike by packing the wrong foods. Here’s a simple guide to help you load up on the good stuff to keep you fueled through your adventure, all the way to the finish. | Cheryl Talbert

Most of us have experienced it. We’ve thrown a mix of trail foods into the pack or bear can, trying to stay within a weight limit or space allowance, but after a few days on the trail nothing looks appetizing and our energy levels crash. For short trips you can often “carbo-load” beforehand, live on energy bars and ramen and a calorie deficit, and come out pleased with a little weight loss. But on extended trips (more than 3–4 days), an ongoing calorie deficit will mean a steady deterioration in your energy and capacity and a high likelihood of a serious “bonk,” potentially spoiling a life-list trip.

So how many calories do I need?

Based on research on metabolic rates for different activities, hikers need to consume from 3,500 to 8,000 calories per day for overnight backpacking trips. This depends largely on their individual pace, the total weight they’re carrying, and the conditions (terrain, elevation, temperature) of their route to keep up with the rate of energy burn.

With careful planning you can create a menu delivering 2,000 to 2,500 calories per pound of food weight per day by diligently aiming for a balance of 40–45% carbohydrates, 40–45% fats and 10–15% protein. Fats are particularly important because they pack nine calories per gram, whereas carbs and protein provide only four. An emphasis on complex carbs and fats is a good strategy for sustained, steady energy delivery. The bonus: this is one situation in which you don’t have to worry about a high-fat, high-carb diet—you will burn it all off!

Modest amounts of protein are enough to maintain muscle, and protein uses more water to metabolize, so a lower percentage is needed in your backpacking diet. Fiber delivers no calories, so in this situation it’s unproductive weight. Also, water content in your trail food drastically reduces the calorie efficiency of the food you carry—and adds pack weight. Instead of fresh fruits, veggies and meats, use freeze-dried or dehydrated versions that can be eaten as is or rehydrated at camp. These components can be dehydrated at home or purchased from many sources online.

How do I design a trail menu to deliver the highest energy and thelowest weight and bulk?

Begin by building a simple spreadsheet to plan daily menus and drill down to the lowest weight for your target calories (see sample menu). Look up your own preferred foods from the website caloriecount.about.com, or from product websites or package labels. Fill in the total serving weight and the weight of carbs, fiber, fats and protein, then experiment to achieve the best overall calories-to-weight ratio that meets your daily calorie target.

What are the most calorie-dense foods to help me keep my food weight down?

Check product labels for these quick indicators of high calorie density:

1. Low water content
2. High nutritive content (% of total weight in
3. carbs, fats and protein, not including fiber)
4. High percentage of grams in fats
5. Lower percentage of grams in protein
6. Low percentage of grams in fiber

Items like olive oil or squeeze margarine can be added to most any meal to boost the calorie density. Many high-density foods also have the advantage of being very compact and durable, such as nuts. Others require practice to pack for easy dispensing and minimum mess, such as nut butters or spreads. Some meal bars and dehydrated meals also have moderately good calorie density and are very simple to pack, but check the labels. They are quite variable in calorie density as well as costly—and you will want to leave the bulky packaging behind.

Conversely, some backpacking staples will surprise you with their low calorie density, such as jerky, oatmeal, brown rice and beans. For beans and oats, this is due to their high fiber content. For others, it is due to their high water content—cooked chicken breast is a good example. Foods in this latter group can be brought to a higher calorie density by dehydrating them or purchasing dried versions.

A low calorie density doesn’t mean a food is “bad.” Any trail menu needs a mix of lower and higher calorie density foods for variety and enjoyment. First and foremost, you need to pack foods that you love to eat, because the least efficient trail foods per unit of weight are those you carry and choose not to consume. Just spend some time evaluating your menu to arrive at the highest average calorie density you can reasonably achieve. It’s time very well spent to ensure that you provide your body the fuel to succeed on the trip you’re planning.