You’re seven miles down the trail. A pack on your back, boots on your feet. Sun streaming in through trees above.
But a time bomb is ticking inside. Your legs are getting heavy. Your breath is labored, feet plodding now, and camp is still five miles to go.
Your tank is on empty. Time to eat. Time to get those calories down. But how to best fuel up?

Adventure racer Mike Kloser downing GU energy gel during a race. Photo: Dan Campbell
Eating optimally while on the go — whether hiking, biking, or climbing a mountain — can be tough. For high-exertion events such as triathlons or ultra-runs, your stomach might protest the very act of securing the sustenance it needs. Indeed, getting the right mix, and the right amount, of carbs, fats, proteins and nutrients can be literally tough to swallow.
But an engine can’t run without fuel. Your body cannot function without food. You need to eat — and eat a lot — to excel at any intense outdoors activity.
“Think of food during athletics and activity as fuel for performance,” said Alicia Kendig, a sports dietitian with Carmichael Training Systems in Colorado Springs. “Focus on carbs to give the body the quick energy it needs.”
Kendig, who has a master’s degree in nutrition and is a registered dietitian, breaks things down quantitatively for her athlete clients, recommending food plans, dosages and times to eat strategically while training or competing.
In general, Kendig said the body can absorb a maximum of 60 to 90 grams of carbohydrates or about 250 to 400 calories per hour. “Every body is different, but those are rough numbers to use as guidelines,” she said.
Nutrition-minded athletes try and maintain those dosages, eating premeasured packets of food or energy bars and gels to meet their hourly quotas.
Carbs from energy bars and gels — including the likes of PowerBars, GU or Clif Shot gel packs — are the preferred fuel for many outdoors athletes, from mountain bikers to trail runners. Kendig said the palatability and convenience of these types of energy foods, which can be eaten quickly without upsetting the stomach, make them ideal for aerobic activity.

Top adventure racers Ian Adamson (left) and Mike Kloser eating pasta during a race. Photographer: Dan Campbell
Fats and protein become more important during longer-duration activities, including backpacking, century bike rides, or daylong ultra races. According to Art Eggertsen, a nutrition advocate and founder of energy-bar company Probar LLC, each long day in the outdoors should begin with healthy food that has a higher ratio of fat and protein. He suggests granola with seeds and nuts, or oatmeal supplemented with a nut butter.
“If possible, you need to start the day with a hearty meal while backpacking or mountaineering,” he said.

