Food is good, but food is heavy. It's one of the biggest contributors to pack weight, especially on long multiday backpacking trips. It's also essential to your happiness, health, and hiking well-being. So how can you pack maximum calories per ounce, minimize total food weight, and still maintain a healthy and interesting diet sufficient for days of hiking exertion?

Feed the furnace
Food consists of three primary components—fat, protein, and carbohydrates—and you need a mix of them all for sustained energy and hiking health. "The fuel your body uses during hiking is a combination of carbs and fat," explains Suzanne Eberle, a board-certified dietician and author of Endurance Sports Nutrition, "but during heavy, anaerobic exertion the only thing the body can burn is carbs. They are premium fuel." Eberle recommends at least 50 percent carbohydrates in any backcountry diet. Fit hikers can hew close to this number; better oxygen uptake means they can burn fat more efficiently during higher sustained levels of exercise. Irregular weekend warriors may want to up their carb quotient or risk running out of gas on strenuous sections of trail.

Don't forget protein
Protein keeps muscles healthy over periods of extended use. "Protein is like the mechanic that comes along and repairs damage at the cellular level as we break apart our muscle fibers during exercise," Eberle explains. "It's what sustains us over the long haul." She suggests 10-15 percent of total calories come from protein. Fat should make up the difference between protein and carbs, usually somewhere between 20 and 35 percent of your total diet. Once you've determined your carb-fat-protein balance, consider the highest-calorie options that meet your dietary needs.

Calorie kings
Pure fat packs 255 calories per ounce, more than twice as much as an ounce of protein or carbs (110 calories). You can use some ultra-high-fat items to prepare your food, like olive oil (240 calories) or butter (200 calories), but you're unlikely to enjoy these as trail snacks. For regular noshing, you need the king of high-calorie trail food: nuts. Pecans and macadamia nuts contain the most energy per ounce (200 calories), followed by Brazil nuts and walnuts (190), hazelnuts (180), peanuts (170), and almonds, cashews, and pistachios (160). (Nut butters closely approximate these calorie counts.) Several seeds follow their nutty brethren, including sunflower and sesame seeds (160 calories). All of them contain a high percentage of fat (at least 50 percent) as well as both carbs (10-20 percent) and protein (20-30 percent).

The energy spectrum
A slew of carb-rich foods hover between 100 and 120 calories per ounce, including dried fruit, pasta, granola, grains like quinoa and rice, and most candy bars and energy bars. Meat jerky, salami, pepperoni, and cheese offer similar calorie counts with higher doses of fat and protein. Some high-fat snack items feature big calorie counts as well, such as peanut M&Ms (145 calories per ounce), milk chocolate (150), or Fritos corn chips (160), though they are not the healthiest options—use them in moderation. Be watchful for food items that drop below 100 calories per ounce, such as most bread products. It usually means they contain some amount of (zero-calorie) water. Overall, you want to aim for an average of 100-120 calories per ounce of food. A calorie count greater than 120 per ounce is achievable, but challenging. (The highest theoretical amount with a 50/35/15 carb, fat, and protein mix is around 160 calories per ounce.)

Refill the tank
How much food do you need? The number of calories you burn during a hike depends on a panoply of factors, including your height, weight, and metabolism, terrain and distance traveled, weather, temperature, and altitude, pack weight, and more. Determining your individual calorie burn can take some practice. The key, however, is to replace the calories you use or risk losing muscle mass. "More than 3 percent weight loss over a trip of a week or more is a sign that you're running a calorie deficit," Eberle notes. "Over time you'll become weaker and have increasing difficulty recovering from day to day. If you're not getting enough calories, it doesn’t matter what mix of food you’re eating." Now that's something to chew on.