An honest energy balance: what a day of foraging and fishing really brings
In films people gather one meal after another in the woods. In reality wild greens, berries and a small fish usually provide less energy than the searching costs – especially in the cold. A healthy adult can survive several weeks without food if they have water, but only a few days without water, and in the cold without shelter often only hours. So the rule is: shelter, water and being found first, save energy, and only look for food where the effort pays off.
- Thinking it through 10 minutes; applies to the whole emergency
Explained simply
Your body is like a stove that always has to burn a little – even when you sit still. It needs energy to stay warm, breathe and keep your heart beating. When you walk, feel cold or carry something heavy, it needs much more. This energy comes from food.
In films there is always enough to eat in the woods. In reality it is very hard. Leaves and herbs are almost only water and hardly fill you up. Anyone who walks through the cold woods for hours to find a few herbs often uses more energy doing so than they eat afterwards.
The good news: a healthy person can survive several weeks without food if they have enough water. Without water it is only a few days, and if you are wet and cold it can become dangerous after just hours. That is why you first look after warmth, water and being found – food comes after that.
How it works
The body constantly burns nutrients to produce heat and movement. Even at complete rest it needs a large part of its energy for breathing, heartbeat, brain and keeping warm. Every movement, every piece of luggage, cold, wind and wet clothing raise the need. For humanitarian planning the Sphere Handbook gives 2,100 kcal per person per day; anyone working hard in the cold needs considerably more.
How much energy a food provides depends on what it is made of. As a rule of thumb, carbohydrates and protein provide about 4 kcal per gram, fat about 9 kcal per gram. Water and fibre provide practically nothing. Wild greens are mostly water and fibre – that is why a whole basket often holds less energy than a chocolate bar. In nature, mainly fatty nuts in autumn and fish are rich in energy.
Without food the body draws on its reserves: first on stored sugar, then mainly on fat and also on muscle protein. This weakens you and makes you more sensitive to cold, but with enough water it can be survived for weeks. Water, on the other hand, the body hardly stores, and hypothermia can become life-threatening in wet and wind after just hours. That gives the order: shelter, water, being found, then food.
What really matters
Honest calculation starts with your own pack. Lay everything edible on a cloth, read the energy values on the packets – kcal per 100 grams times weight – and divide by the number of people. Usually the supplies last longer in small portions than you think. Knowing this takes the pressure off and prevents hectic, dangerous searches.
Before every search for food, ask yourself four questions: How far do I have to go? How long will it take? How wet and cold will I get? How great is the risk – falling, getting lost, mixing plants up? Only what is close to camp, quick to fetch, reliably identified and plentiful is worth it. A bush full of ripe berries right by camp: yes. A two-hour walk for a handful of herbs: no.
Saving energy is often more effective than searching for it. Anyone who stays in one place where they can be found, rests a lot, keeps dry, insulates themselves from the ground and sleeps warmly needs much less. Work slowly enough that you do not sweat, because wet clothing chills you and costs extra energy. Every calorie you do not use is one you do not have to find.
Safety: what to watch out for
Hunger changes how you think. Anyone who has eaten little becomes impatient, irritable and accepts more risks. That is exactly when plants get mixed up, steep slopes get underestimated and camps get abandoned. Be aware of this trap and make important decisions rested if possible and together with others. Eat nothing you do not identify 100 % – a poisoning costs far more than any meal can bring.
The body needs water to process food, especially protein-rich food such as fish and meat. If water is scarce, eat little and save protein-rich food for later. Weakness, dizziness when standing up and feeling cold are normal effects of eating little and a reason to rest even more. Confusion, violent shivering or fainting are emergencies: call 112, in Austria also 144, and in the Austrian mountains also mountain rescue on 140.
After many days with almost no food, the body has switched to saving mode. Sudden, plentiful eating can then overwhelm it. That is why you start again slowly with small portions and seek medical help. Children, older and ill people have smaller reserves than healthy adults – they need help sooner and are looked after first in a group.
When it makes sense – and when it does not
Looking for food makes sense when shelter, water and signal are secured, the emergency is likely to last longer and something worthwhile can be found near camp – ripe berries, nuts in autumn or, where legal or in genuine danger to life, fish. In a group it is best if one person who knows the plants well gathers while the others look after fire, shelter and signal.
Looking for food makes no sense in the first hours after getting lost, in cold, wet or darkness, when you are injured, or if you would have to leave the place where people are searching for you. In these situations hunger is unpleasant, but it is not the danger. The danger is chilling, lack of water or an accident while searching.
The best energy balance is made at home. A small, energy-dense emergency ration in your pack, warm protection and a trip plan left behind weigh little and replace many hours of searching. Anyone prepared like this hardly has to think about food in a real emergency.
Good to know
The US Army survival manual (FM 3-05.70) stresses that although you can live several weeks without food, physical and mental performance declines quickly without it. Exactly how long depends on body reserves, health, temperature and water – which is why this entry gives no exact figure.
The energy needs of individual people vary greatly. The FAO/WHO/UNU expert report describes how they rise with body size, age and physical activity. Planning figures like the 2,100 kcal from the Sphere Handbook are averages for large groups, not an exact calculation for you.
Hunger is also in the head. Fixed mealtimes, small portions, a warm drink and shared rituals help you stay calm. Anyone who knows they can hold out for a long time makes better decisions than someone who sets off out of fear of starving.
Step by step
Stop and set priorities
Stop, take a breath and ask yourself in this order: Am I injured? Am I protected from cold, wet and wind? Do I have safe water? Can I be found – emergency call, trip plan, signal? Only once that is solved does food become a topic.
- 1
Stop and set priorities
Stop, take a breath and ask yourself in this order: Am I injured? Am I protected from cold, wet and wind? Do I have safe water? Can I be found – emergency call, trip plan, signal? Only once that is solved does food become a topic.
- 2
Know your own need roughly
As a planning figure the Sphere Handbook gives 2,100 kcal per person per day. Hard work, cold, wet clothing and carrying loads raise the need considerably; rest, warmth and sleep lower it. This figure is not a target you must reach outdoors but a yardstick for judging what you find.
- 3
Count your supplies honestly
Lay everything edible from your pack on a cloth and read the energy values on the packets: kcal per 100 g times weight. Divide that by the number of people. That way you know how many days your supplies last in small portions – usually more than you think.
- 4
Judge finds realistically
Wild greens such as nettle or wood sorrel are almost only water and fibre and hardly fill you up. Berries provide some sugar, but little per handful. Only fatty nuts in autumn and – where legal or in genuine danger to life – fish are rich in energy. A chocolate bar from your pack often holds more energy than a whole basket of wild greens.
- 5
Weigh effort against gain
Before every search ask: How far do I have to go, how long will it take, how wet and cold will I get, how high is the risk? Only what is close to camp, quick, reliably identifiable and plentiful is worth it. Walking through the woods for hours for a handful of herbs costs more than it brings, and you move away from the place where people are searching for you.
- 6
Save energy
If possible, stay in one place where you can be found. Rest a lot, work in the warm hours of the day and slowly enough that you do not sweat. Keep dry, insulate yourself from the ground and sleep as warmly as possible. Every calorie you do not use is one you do not have to find.
- 7
Think about food and water together
The body needs water to process food – especially protein-rich food such as fish and meat. If water is scarce, eat little and save protein-rich food. Divide the supplies you have into small, regular portions and share them fairly in a group.
- 8
Take warning signs seriously
Weakness, dizziness when standing up, feeling cold, irritability and slow thinking are normal effects of eating little – they are a reason to rest even more, not to search even more. Confusion, violent shivering or fainting are emergencies: call 112 (in Austria also 144). After a long time with almost no food, start again slowly and seek medical help.
Common mistakes
- Going to look for food straight after getting lost instead of building shelter
- Walking for hours for a few herbs
- Leaving the place where people are searching
- Eating uncertain plants out of hunger
- Getting sweaty while foraging
- Eating protein-rich food although water is scarce
- Suddenly eating a lot after long starvation
Quick view
Materials
Dry spare clothing
Staying warm saves energy
Carry it in waterproof packaging – wet clothing barely insulates.
Sleeping bag
Do not store compressed long-term; do not pack away damp.
Suitable for
- Lost or injured in the terrain, waiting for rescue
- Planning trips and emergency rations
- Groups that need to decide who does what
Not suitable for
- Medical nutrition advice or fasting during illness
- Infants, pregnant women, the chronically ill – stricter limits apply to them
- As encouragement to go hungry on purpose
Prerequisites
- Willingness to calculate honestly rather than hope
- Knowing what food you have with you
Safety
- Hunger makes people careless. Anyone who is weakened is more likely to confuse plants, fall and make poor decisions. Eat nothing you do not identify 100 % – a poisoning costs far more than any meal can bring.
- After many days with almost no food, start again slowly with small portions and seek medical help – sudden, plentiful eating after long starvation can be dangerous. Children, older and ill people have smaller reserves and need help sooner.
How it works
The body needs energy even at rest to stay warm, breathe and keep the heart beating; movement, cold and work raise the need. For humanitarian planning the Sphere Handbook gives 2,100 kcal per person per day – anyone working hard in the cold needs more. Wild plants are mostly water and fibre and provide little energy per handful; fat provides about twice as much per gram as carbohydrates or protein. Foraging only pays off when the gain is bigger than the effort. Without food the body lives on its reserves – this weakens you, but with enough water it can be survived for weeks.
Advantages
- Prevents dangerous decisions made out of hunger
- Saves strength for what really matters
- Helps when packing food for trips
Disadvantages
- Hunger remains unpleasant and weighs on morale
- No exact figures possible for individuals
Deep knowledge
Background
The US Army survival manual (FM 3-05.70) stresses that although you can live several weeks without food, physical and mental performance declines quickly without it – and that water is far more urgent. The FAO/WHO/UNU expert report on human energy requirements describes how needs rise with body size, age and physical activity; the Sphere Handbook turns this into the planning figure of 2,100 kcal per person per day.
How long a person survives without food depends heavily on body reserves, health, temperature and water. That is why we give no exact figure – only the cautious statement “several weeks with water” for healthy adults.
Variants
- In a group
- In a group, not everyone gathers for themselves. One person who knows the plants well gathers near camp; the others keep fire, shelter and signal going. Supplies are counted together and shared fairly; children and the injured are looked after first.
- Plan beforehand
- The best energy balance is made at home: a few hundred grams of energy-dense emergency ration, warm protection and a trip plan left behind weigh little and replace many hours of searching.
Common mistakes
- Going to look for food straight after getting lost instead of building shelter
- Walking for hours for a few herbs
- Leaving the place where people are searching
- Eating uncertain plants out of hunger
- Getting sweaty while foraging
- Eating protein-rich food although water is scarce
- Suddenly eating a lot after long starvation
Limits and risks
- No energy values for individual wild plants – the values vary widely
- No recommendation to fast
- Does not apply to infants, pregnant women and the chronically ill
Material alternatives
Derived from material properties: a substitute must have all relevant properties. Observe the notes on the substitute.
- Dry spare clothing
- Sleeping pad, Dry leaves, grass or conifer boughs (Collect only where allowed; no protected plants. Check for ticks and insects.), Backpack, Wool blanket / duvet (Keep away from candles, stoves and heaters.), Insulated cool box (Keeps cold only for a limited time; without ice packs or ice it is not a fridge.), Sleeping bag (Do not store compressed long-term; do not pack away damp.), Newspaper and cardboard (Flammable – keep away from candles, stoves, heaters and embers.), Insulated cooking box (hay box, thermal cooker) (Never put open flame or embers inside – only the hot, closed pot.), Long-stemmed thatch (reed, grass, rushes) (Extremely flammable – no open fire and no sparks nearby.)
- Sleeping bag
- Sleeping pad, Dry leaves, grass or conifer boughs (Collect only where allowed; no protected plants. Check for ticks and insects.), Backpack, Dry spare clothing (Carry it in waterproof packaging – wet clothing barely insulates.), Wool blanket / duvet (Keep away from candles, stoves and heaters.), Insulated cool box (Keeps cold only for a limited time; without ice packs or ice it is not a fridge.), Newspaper and cardboard (Flammable – keep away from candles, stoves, heaters and embers.), Insulated cooking box (hay box, thermal cooker) (Never put open flame or embers inside – only the hot, closed pot.), Long-stemmed thatch (reed, grass, rushes) (Extremely flammable – no open fire and no sparks nearby.)
Results come exclusively from structured entries. No improvised instructions are generated.
Sources
Headquarters, Department of the Army (USA) (2002): FM 3-05.70 Survival
Several weeks without food survivable, but rapid loss of performance; water is more urgent than food
Sphere Association (2018): The Sphere Handbook: Humanitarian Charter and Minimum Standards in Humanitarian Response
Planning figure of 2,100 kcal per person per day
Food and Agriculture Organization of the United Nations (FAO) (2004): Human energy requirements – Report of a Joint FAO/WHO/UNU Expert Consultation
Energy requirements depend on body size, age and physical activity
John E. Hall – Elsevier: Guyton and Hall Textbook of Medical Physiology
Energy metabolism, energy content of fat, carbohydrate and protein, starvation metabolism
Wilderness & Environmental Medicine (Wilderness Medical Society) (2019): Wilderness Medical Society Clinical Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2019 Update
Hypothermia as an acute danger in cold and wet