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What To Know About Hiking In A Fasted State

After researching and practicing fasting for a few years, I understand the mechanisms and benefits of fasting. Therefore, I like to help others understand how fasting affects us when hiking, and if they would like, how to add it to their hiking routine.

Before we get started, I want to answer this one question. Is it dangerous to hike in a fasted state?

Hiking in a fasted state is not inherently dangerous. Our bodies require energy, which we normally get when eating. However, when fasting, our bodies use stored fat for energy. It is sound practice when fasting to “build your fasting-muscles”* before attempting on a backpacking trip.

*Megan Ramos of The Fasting Method

Let’s take a closer look at fasting; what does fasting truly mean? And how to use it successfully on your next backpacking trip.

[If you are interested in learning the science behind fasting – check out The Obesity Code by Dr. Jason Fung]

Fasting is the Voluntary Abstaining From Food

Simply put, fasting means voluntarily abstaining from food for a set period. The simplest form of fasting happens between dinner and breakfast. A few hours after eating, our body switches from digestion to fat-burning to provide energy while we sleep.

People fast for a myriad of reasons. Many people fast for religious or spiritual reasons, others fast for weight loss, and still, others fast for clarity and focus. Whatever the reason, your body undergoes several hormonal changes allowing you to fast for a lengthy period without keeling over.

Two Types of Fasts: Intermittent and Extended

For the most part there are two types of fasts, intermittent and extended.

Intermittent fasting

In recent years, intermittent fasting (IF) has become very popular. It has many health benefits, including weight loss and mental clarity. People who practice IF do so in a few ways.

Depending on their goal, people manipulate the lengths of fasting and eating windows. For example, 16/8. When on a 16/ 8 IF, you fast for 16 hours then have an eating window of 8 hours. The same holds for 18/6, 20/4, 36 hour, 42 hour, and 72-hour fasts.

Also, there is OMAD and 2MAD standing for One Meal a Day and Two Meals a Day.

So, you see, people choose different IF lengths to fit their lifestyle and goals.

fasting and lifestyle goals

Extended fasting

Extended fasting is often reserved for serious medical problems, like severe obesity and diabetes. These fasts can last 5, 7, or 10 days. I have fasted for as long as 10 days with only positive effects. During this time, I lost 16 pounds and had an easy time foregoing food for the entire fast.

Before we dive into hiking while fasting, let’s learn what happens when we fast.

Hormonal changes with fasting

Hormones regulate every system in our body, including fat and carbohydrate burning. Simply stated, our bodies either burn or store fat.

Insulin and fat burning

The hormone that helps regulate fat usage and storage is insulin.

When we rely on carbohydrate-rich food sources, insulin reacts to remove excess sugar from the bloodstream and store it as fat for later use. When you rely on carbohydrates, coupled with regular eating intervals (frequent eating throughout the day), your body gets used to this system.

Carbohydrate dependence

You become carb-dependent. Meaning, you rely on sugars as your form of energy. Unfortunately, as many marathoners can attest, you only have so much glycogen (stored sugar) before you “hit the wall.”


Instead, fasting and eating a low carbohydrate, high-fat diet reduces insulin levels. Additionally, sugar becomes less available, and fat becomes our primary energy source. Over time our body becomes fat-adapted, and it is much easier to fast for lengthy periods.

What happens when fasting?

When hiking or performing a moderate aerobic activity, we use about the same amount of carbohydrates as fat for energy. Our body actively recruits and readily uses the available energy source at the moment.

As we reduce our reliance on food during fasting, our bodies switch from burning sugars to utilize fat for energy. When fasting, we rely heavily on fat for energy, and our system runs smoothly.

The nice thing about fat burning is that most of us could hike for a thousand miles before running out of fat. We know from research that it takes 3,500 calories to burn one pound of fat.

Using an average 130-pound woman and a 170-pound man, we find that when hiking at a moderate pace, our examples can hike about 731 and 622 miles respectively, burning primarily fat stores. See the chart below for the details.

Estimating miles hiked using body fat for energy, demonstration purposes only.

We are capable of great feats of endurance relying on fat as our energy source. However, we shouldn’t attempt to exhaust all of our fat stores on a single monster hike. However, it is true we can hike a long time while fasting.

During my 10-day fast, I did many short day hikes without difficulty. The biggest concern for me while fasting is maintaining my fluid/ electrolyte balance. Let’s look at that.

How to Hike Safely While in a Fasted State

Now we know what happens from a hormonal standpoint when fasting, let’s take a closer look at hiking in a fasted state; what it means, and how to do it safely.

Hiking is an endurance activity. Meaning, our muscles work in a low to moderate capacity for a long period. To work efficiently, muscles require electrolytes. Electrolytes are electronically charged minerals, like sodium, potassium, and magnesium. They help our muscles work efficiently.

Our bodies need to keep our electrolyte levels in check. If not, muscles will cramp up, so it is important to replace them as we go. We replace our electrolytes with mineral-rich foods and balance it by drinking ample water.

However, when we fast on a hike, electrolytes aren’t replenished with food because there isn’t any. Our water levels rise, and our electrolyte levels fall.

If this water to electrolyte imbalance worsens we risk hyponatremia. Hyponatremia is a state of imbalance when our water level is too high relative to the sodium level in our bloodstream. Symptoms of hyponatremia can range from mild to severe and can be life-threatening. Symptoms include nausea, vomiting, headache, confusion, muscle weakness, cramps, spasms, seizures, and even coma.

Three steps to prevent hyponatremia when fasting

As we hike, we use our stores of electrolytes. Therefore, we need to replace them continually. To do this, I have found a few ways without introducing food that will break our fast.

First, salt tablets added to water is a good start. Doing this will maintain sodium balance. However, it neglects potassium and magnesium.

Second, use Himalayan Sea Salt. Unlike table salt, Himalayan Sea Salt is packed with minerals, including magnesium. However, it does not contain potassium.

Third, I have found a great concoction called Ketorade. I first heard of this from keto expert, Dr. Ken Berry. He and his wife developed this drink specifically for the keto diet, but it works for fasting as well. It contains sodium, potassium, magnesium, and acetic acid.

The recipe is simple, and it helps replenish electrolytes while out on the trail. Here is a brief and entertaining video from Ken and Neisha Berry on Dr. Berry’s YouTube channel.

How to get started fasting

There are many types of weight loss plans, however, fasting is the easiest to manage. When you fast, it is not about what you eat (nothing) but when you eat. Therefore, the easiest way to begin is to choose your type of fast.

For most people, intermittent fasting is the best way to get started. A couple of guidelines include:

  1. Eat until full during your eating window. Do not hold back. Remember that while you hike in a fasting state, you burn fat for energy. When you eat to break your fast, you don’t need to make up for the many hours of fasting. Eat your normal diet of low-carb/ healthy fats. We will discuss this later in the article.
  2. Do not eat anything during your fasting window. Eating even a couple of nuts and berries breaks your fast. So, drinking water, taking in electrolytes during your fast is the best way to get the fasting benefits.

Choose your fasting regimen. Let’s start with 16/8 fasting. In a 16/ 8 fast, we have an eating window of 8 hours. Meaning, we eat 2 or 3 meals between the hours of 10 a.m. to 6 p.m., for example. During this period we eat until we are full, don’t snack, and then wait until the next meal.

The best way to accomplish this is to wake up, get everything ready for the day, and drink a cup of black coffee or tea (without cream or sugar). Then at 10 a.m. stop for a moderate to large breakfast/ snack. A great way is to eat a high-calorie energy bar like those from Greenbelly. Their meals-to-go are loaded with calories.

Water and electrolytes are the most important needs when fasting

As we stated earlier, your most important needs are water and electrolytes. If you are doing an extended fast, 5 to 7 days for example, then you need to add vitamins to this regimen.

On shorter fasts, your body has enough stored vitamins to avoid depletion and subsequent deficiencies. You will not get scurvy on a short fast.

Also, water needs vary, but the general rule of thumb is 1.5 quarts per hour of hiking.

Getting better at fasting is about practice, practice, practice

Picture fasting as exercise. The more often we fast, the better we get at it. Over time our bodies adapt to a fasting regimen. Starting a fasting regimen at home helps your body adapt before hitting the trail.

Skipping breakfast and stopping eating at 6 p.m. starts your adaptation before your trip. One word of caution though; Many people try to use fasting to reduce caloric intake. Dr. Jason Fung, a nephrologist and author of The Obesity Code, advises against this.

While we do use fat for energy, we still require vitamins, minerals, and proteins at a higher level when hiking. So, eat until full. Don’t try to reduce calories because over time our metabolism will slow to meet the restriction in calories.

I wouldn’t advise that you start fasting on your hike. This is a recipe for disaster; Pun intended. Our bodies take time to adapt. If we don’t allow that time before our hikes, we will be miserable. Practice fasting well before the hike. Get used to it and extend your fasting over time.

What to eat during your eating window?

Whether we are fasting or not, our daily caloric needs don’t vary when hiking. During a fast, we get our energy from burning our body fat. However, we still require proteins, minerals, water, and vitamins every day. Therefore, the best way to get the calories we need is to eat food dense in nutrients and calories.

eating healthy foods while fasting
healthy foods

Eating a low carbohydrate and high-fat diet is the answer to hiking well. Carbohydrate choices should be whole foods and not sugary energy bars. These foods include nuts, berries, and whole grains. Protein is necessary to maintain muscles during the hike. And fat provides the energy to hike all day.

But why not more carbohydrates? From a calorie standpoint, proteins and carbohydrates provide 4 calories per gram each. However, fat carries a whopping 9 calories per gram and contributes more than twice the energy than carbohydrates. Additionally, fat satiates you better than carbohydrates.

Often, people who eat carbohydrates regularly get hungry quickly and have trouble staying satiated for more than a few hours. On the contrary, people who eat high-fat meals stay satisfied and full of energy for extended periods. I find that if I eat a high-carb meal before hiking, I have much less staying power than when I eat a high-fat meal.

To take this one step further, I have hiked as many as 8 hours in the White Mountains of New Hampshire without eating at all. I drank water and pickle juice during the trek. I was full of energy the entire hike.

How to approach different types of hikes when fasting

Remember that the reasons to hike in a fasted state are as follows: To use stored fat for energy and to maintain focus and clarity during the hike. So, different trips require different fasts.

For our purposes, we divide hikes into 1. day/ weekend hikes, 2. week-long hikes, and 3. thru-hikes.

Fasting during a one to 3-day hiking trip

On a day hike, it is pretty easy to skip breakfast and go hiking. When you reach the top of the local mountain, eat lunch. Hike down, and eat dinner. Also, you could try skipping breakfast, hiking then eating when the hike is completed. When I am fat-adapted, I enjoy this form of fasting.

A weekend hike, do the same as the day hike but stop eating at 6 or 8 p.m. and don’t eat again until 10 a.m. or 12 p.m to accomplish a 16/ 8 fasting schedule.

The benefits of these short fasts include increased focus and some mild fat burning.

Fasting during weeklong backpacking trips

Following a 16/8 fasting regimen is similar to the weekend trip. It is important to eat your daily calorie requirements. Carrying the appropriate high-fat, low carb foods is paramount to maintaining energy during this trip.

The benefits of longer fasting during thru-hikes include greater weight loss and more clarity and focus during the trip.

Fasting during thru hikes

thru-hiking requires ever increasing caloric needs. it is difficult to fast when thru-hiking.

As backpacking trips lengthen, our caloric needs increase as well. It becomes more difficult to get enough calories. So, it is much more important to plan out meals that are super high in fat and carry enough protein to prevent muscle loss.

Additionally, fasting may become more difficult to maintain on longer hikes. The reason for this is that our bodies burn more calories over time. And keeping up with this demand becomes more difficult.

Our advice is that instead of grazing throughout the day, you continue to eat large high-fat meals during your eating window and skip snacking. This way, insulin stays in check and energy stays level.

Frequent eating causes insulin to spike at high levels. As noted earlier, when insulin levels rise, we store fat and rely on sugars for energy.

The benefits of fasting on thru-hikes include reliance on fat for energy, increased weight loss, and continued steady focus.

When to stop fasting

While fasting has many benefits, some discomfort from hunger pangs is normal. Also, headaches and flu-like symptoms, while uncomfortable, are not reasons to stop fasting. They may be signs of early electrolyte imbalance or even withdrawal from sugar.

But according to the Fasting Method with Megan Ramos, there is one symptom from fasting that you should not ignore: nausea.

Here is what she says:

Nausea usually occurs because you’ve become too dehydrated.  Either your electrolytes have become too depleted or the concentration of ketone bodies (fuel source produced by burning fat) in your blood has become too high.

Megan Ramos, The Fasting Method – When to Stop Your Fast

Before you backpack in a fasted state, understand the symptoms that might occur and what to do about them.

Who should not fast during hiking?

Fasting is beneficial in many circumstances. However, some people should not fast. According to Dr. Jason Fung of The Fasting Method, children and pregnant women should not fast.

If your child is heavy or obese, Dr. Fung suggests reducing sugary snacks and not eating between meals as the first line of defense against obesity. Because children are still growing, they require extra nutrients, and fasting is not appropriate.

Also, pregnant women require extra nutrients for the baby. So, fasting is not appropriate for this population.

Common misconceptions about fasting and hiking in a fasted state

Many people believe that fasting will cause serious damage. They think that skipping a meal is the end of the world. Have you heard the saying, “breakfast is the most important meal of the day?” Well, yes, breaking your fast is important, but it doesn’t have to be first thing in the morning.

Many breakfast cereal companies promote the notion that eating breakfast gives you energy for the day. Unfortunately, they also sell highly processed, sugary foods that spike your insulin and leave you feeling lethargic.

Additionally, after coming off your insulin spike, you are left feeling hungry again. So, to combat this, the food industry says you need to eat frequently throughout the day. That is hogwash!

Yes, we are designed to eat. But we don’t need to eat every 2 or 3 hours. We crave sugar when we fill ourselves with high sugar foods. Because of this, we believe that we need to eat frequently.

However, eating highly nutritious, high-fat foods keep up satisfied without spiking our sugar and insulin levels. Eating this way lets us go for hours without eating.

What is hiker hunger?

Hiker hunger is an extreme sense of hunger without the accompanying caloric needs. What this means is hikers feel super hungry for a long time after hiking something like the Appalachian Trail or Pacific Crest Trail.

Many people equate this to the high caloric needs required to perform sustained high-level activity for months. However, is there more to this?

While people require anywhere from 3,000 to 6,000 calories per day, they often get those calories from foods “rich” in processed carbohydrates and simple sugars. These processed calories are mostly void of the nutritional value needed every day. Over several weeks or months, this deficit worsens. And hiker hunger takes over.

Many hikers succumb to the pressure by eating massive quantities of food. Unfortunately, many choices are void of nutrients like pancakes and syrup, or pasta with high sugar marinara sauce.

How to prevent hiker hunger during thru hikes

As we stated earlier, a low carb, high fat, moderate protein diets help stave off hiker hunger appropriately. But remember, the carbs should be nutrient-dense and the proteins real.

Recommended Macro Percentages
Fat40 to 70 Percent
Protein15 to 30 Percent
Carbohydrate15 to 30 Percent

Many ‘energy bars’ suggest that their proteins and nutrients are the highest level and will provide what the body needs. However, most are just nuts, seeds, and raisins covered with sugar.

It is best to learn about what you need. Also, don’t fall victim to the food companies saying this and that about their monetized sugar.

What do backpackers say about fasting?

I scoured the internet to see what backpackers say about fasting. Many are on board, while others don’t think it is necessary.

9 hiker quotes by hikers who have fasted during hikes

  1. “no noticeable drops in energy or changes in hunger”
  2. “keep in mind lots of hiking food is high on the glycemic index.”
  3. “doing it to feel good…not to suffer unnecessarily”
  4. “belief in calories being the answer” – again, when adapted tend to use fat and not sugar for energy.
  5. “I barely ever eat breakfast on section hikes anyway”
  6. “Just got off the CT and I found that I could not fast on the trail. I usually eat between 12 and 6 with no problem fasting until then. But after a couple of days on the trail, I found that I would be extremely hungry and need a snack in the morning or else I’d get a terrible crash. It wasn’t much, usually just a bar or a handful of nuts but I needed something.”
  7. “lost a pound per day on a 5-day hike, wouldn’t suggest fasting”
  8. “packing in 4,000 calories in your eating window is hard when backpacking”
  9. “I am completely adjusted to IF…find that I have a hard time with digestion when I follow conventional wisdom [high carb, low fat]”

Final thoughts about hiking in a fasted state

burgers and fries aren't the best for breaking a fast

I find it interesting that conventional wisdom (eating frequent high carbohydrate/highly processed meals) may be a roadblock to someone thinking about fasting for the first time. But at the same time, thru-hikers gorge on pancakes, pasta, pizza, french fries, and other high carbohydrate foods, and it leaves them seeking more.

The term insanity comes to mind. It is doing the same thing over and over expecting a different outcome. When hikers report hiker hunger but eat only highly processed foods, it is no wonder the cycle continues for months.

I have found that when we fast, we free ourselves of the sugar cravings; and when we eat high fat, low carb meals, we replenish our bodies with what it needs and wants on a daily basis.

My advice for hiking in a fasted state

Start at home slowly. Skip breakfast for a week. Stop snacking in between meals. Slowly build up your tolerance to fasting. And start making better food choices. Ones that are higher in fat, lower in processed carbs, and provide the right amount of protein.

Over time your body will know what it needs and wants to sustain your energy. Fasting gets easier over time. Start slow and stick to it. Then when you want to try it on the trail, it isn’t such a big deal.