After researching and practicing fasting for a few years, I understand the mechanisms and benefits of the process. Therefore, to help others understand how fasting affects us when hiking, I want to provide you with everything you need to know about hiking in a fasted state.
Hiking in a fasted state is not inherently dangerous. Our bodies require energy, which we normally get from eating. However, when fasting, our bodies primarily use stored fat for energy. You should slowly adjust your body to the fasted state before attempting it on a hiking trip.
Below, I’ll go through everything you need to know about hiking in a fasted state. This will not only let you decide whether or not fasting is right for you, but it will also ensure you understand how to fast safely for any hiking trip. But first, let’s give an overview of what fasting actually is.
What Is Fasting?
Simply put, fasting means voluntarily abstaining from food for a set period. The simplest form of fasting happens between dinner and breakfast the next day. A few hours after eating, our body switches from digestion to fat-burning to provide energy while we sleep.
People fast for many reasons. Many people fast for religious or spiritual reasons, others fast for weight loss, and some people fast for clarity and focus. Whatever the reason, your body undergoes several hormonal changes, allowing you to fast for a lengthy period if you do it properly and safely.
What Happens When You Fast?
When hiking or performing a moderate aerobic activity, we use both carbohydrates and fat for energy. Our body actively recruits and readily uses the available energy source at that moment.
As we reduce our reliance on food during fasting, our bodies switch from burning sugars to utilizing fat for energy. You need to burn about 3,500 calories to burn one pound of fat. You can burn about 350 calories per hour by walking at a moderate pace, and this varies from person to person.
Plenty Of Fat Reserves
This means you’d need to do about 10 hours of walking to burn a pound of fat, and that’s if you’re not taking on any more calories within that time (i.e. fasting). The average person might have 30 or more pounds of fat in their body. So, even if you could hike for days on end in a fasted state, you wouldn’t run out of fat to burn very quickly (unless you have a very low body fat percentage).
However, this does make fasting combined with exercise a great way to lose weight if you do it safely. But just because your body can start using fat reserves for energy in a fasted state, that doesn’t mean you should go out and hike in a fasted state right away.
Take Your Time
It takes time for your body to adjust to a fasted state. Many people exhibit mood changes even after going just a few hours without food. So, going without food for a large part of the day without getting your body used to that state can lead to unpleasant mental states, and you will most likely feel physically weak too, which clearly isn’t great for hiking.
It can take several weeks for your body to “adjust” to a fasted state. So, don’t rush into it, and instead find a pattern of fasting that works for you before you try and do any major exercise or hikes in a fasted state. Fasting isn’t for everyone, and you may just find it doesn’t work for you.
Intermittent vs Extended Fasting For Hiking
In recent years, intermittent fasting (IF) has become very popular. It can offer many health benefits, including weight loss and mental clarity. People who practice IF do so in a few ways.
Depending on their goal, people change the lengths of their fasting and eating windows. One of the most common systems is the 16/8 method. When on a 16/8 intermittent fasting regime, you fast for 16 hours then have an eating window of 8 hours. The same idea holds for 18/6, 20/4, 36-hour, 42-hour, and 72-hour fasts.
There are also methods such as OMAD and 2MAD, standing for One Meal A Day and 2 Meals A Day respectively, both being self-explanatory. People choose different IF lengths to fit their lifestyle and goals. This is an important point for those considering hiking in a fasted state. You need to pick a system that suits you and your hike, and your own physiological responses to 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.
However, this won’t be the case for everyone, and you shouldn’t attempt a 10-day fast without any prior fasting experience. To understand why, let’s take a closer look at the different effects of fasting.
Hormonal Changes With Fasting
Hormones regulate every system in our body, including the burning of fat and carbohydrates.
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.
You can then become apparently “carb-dependent”. This means you mainly 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.”
Fasting and eating a low carbohydrate, high-fat diet can reduce your insulin levels. Additionally, sugar becomes less available, and fat can become your primary energy source. Over time, your body can become fat-adapted, and it can get progressively easier to fast for longer periods of time. This is why it’s important to start small, and work your way up to longer fasts, be it extended or IF.
How To Hike Safely While In A Fasted State
Hiking is an endurance activity, meaning your 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.
Our bodies need to keep our electrolyte levels in check. If not, muscles will cramp up, and you can even experience more serious side effects like blood clots, so it is important to replace them as you use them up. We replace our electrolytes with mineral-rich foods and balance it by drinking enough water.
However, when we fast on a hike, electrolytes aren’t replenished through food because you’re not consuming any. Your water levels rise, and your electrolyte levels fall.
If this water to electrolyte imbalance worsens, you 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 comas.
How To Prevent Hyponatremia When Fasting
As we hike, we use our stores of electrolytes. Therefore, we need to replace them continually. Adding salt tablets to your water will maintain sodium balance, but not that of other minerals. Unlike table salt, Himalayan sea salt is packed with minerals, including magnesium, which can be a good alternative.
However, it’s not just an electrolyte imbalance you need to consider. When exercising in a fasted state, your body can actually start breaking down proteins in your muscles for fuel, rather than fats.
You can also end up just having less energy to do things if your body hasn’t adjusted to burning stored fat, which can leave you feeling weak. You may also just not be able to keep up the pace. This reemphasises the importance of breaking your body into fasting, rather than trying to do too much at one time.
How To Get Started Fasting
For most people, intermittent fasting is the best way to get started. If you’re doing this, it’s best to eat until you’re full during your eating window. This ensures your body has enough stores of energy to keep you going during your fasting period.
Do not eat anything during your fasting window. Eating even a couple of nuts and berries breaks your fast. So, drinking water and taking in electrolytes during your fast is the best way to get all of the benefits of fasting.
Choose your fasting regimen carefully. In a 16/8 fast, you have an eating window of 8 hours. You can eat 2 or 3 meals between the hours of 10am to 6pm, for example. During this period, eat until you are full, don’t snack, and then wait until the next meal. If 16/8 doesn’t work for you, play around with the durations until you find what suits.
Water And Electrolytes
As we stated earlier, your most important needs when fasting are water and electrolytes. If you are doing an extended fast, 5 to 7 days for example, then you need to add various vitamins to this regimen too. On shorter fasts, your body has enough stored vitamins to avoid depletion and subsequent deficiencies. You will not get scurvy on a short fast, unless you already have vitamin deficiencies.
The more often your fast, the better you will get at it. Over time, our bodies can adapt to a fasting regimen. Starting a fasting regimen at home helps your body adapt before hitting the trail.
How To Approach Different Types Of Hiking When Fasting
1-3 Day Trip
On a day hike, it is pretty easy for many people to skip breakfast and go hiking. When you reach the top of the local mountain, eat lunch. Hike down, and then eat dinner. You could try skipping breakfast, completing the hike, then eating when you’re done.
For a weekend hike, do the same as the day hike but stop eating at 6 or 8pm and don’t eat again until 10am or 12pm to stick to a 16/8 fasting schedule (adjust to suit your chosen regime). The benefits of these short fasts can include increased focus and some mild fat burning.
Fasting For Longer Trips
It is important to eat your daily calorie requirements when intermittent fasting, especially if you’re doing a lot of exercise, such as on a hike. Carrying the appropriate high-fat, low carb foods with you is paramount to maintaining energy during this trip.
The benefits of intermittent fasting during longer hikes can include greater weight loss and more mental clarity and focus during the trip. Extended fasting for longer hikes is generally not advised for beginners, unless your body is well-adapted to burning fat already.
Fasting During Thru Hikes
As hiking trips lengthen, our caloric needs increase as well. It becomes more difficult to get enough calories throughout the eating window while still staying on the move. So, it is much more important to plan out meals that are high in fat and carry enough protein to prevent muscle loss.
Frequent eating throughout the day can cause insulin to spike at high levels. When insulin levels rise, we store fat and rely on sugars for energy. The benefits of fasting on thru hikes can 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. However, these uncomfortable symptoms are best suffered by practicing fasting in advance of your hiking trip, to limit their impact on your hike.
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. Before you backpack in a fasted state, understand the symptoms that might occur and what to do about them.
However, if you feel excessively weak, are struggling with dizziness, or general discomfort that makes hiking unpleasant, you should stop fasting.
Who Should Not Fast During Hiking?
Fasting is beneficial in many circumstances. However, some people should not fast. Young children and pregnant women should not fast. Because children are still growing, they require extra nutrients, and fasting is not appropriate. Pregnant women require extra nutrients for the baby, so fasting is also not appropriate in this case.
Hiking in a fasted state is safe if you understand how to do it properly. It’s best to get your body used to fasting well in advance of your hiking trip. You need to find a fasting regime that suits your body, and this takes practice. Hiking in a fasted state can aid weight loss and mental clarity.