Wilderness Survival and Caloric Intake
As I've previously discussed, one of the main targets for us while surviving in the woods will be getting enough calories to manage well. To refresh your memory, the average 70 KG man (154lbs) needs around 2100 calories a day for maintenance. That figure is too optimistic for someone surviving in the woods. Without infrastructure, many traps created, supplies to draw from, abundant game, vegetable and fruit and nut sources, and something I call unmentionables, the maximum amount of calories for an expert hunter/gatherer will most likely be around 1500 calories. Of course, you will hit days of abundance. You'll find something and store it, using some of that to supplement on following days. Or you'll eat very well, and not eat anything the next day for a variety of reasons.
Maintaining 1500 calories in a perfect setting of safety and low energy output is tolerable. As anyone knows who has dieted, it is uncomfortable. When the body sees a change in diet, it adapts. This is not a rapid process. There are enormous amounts of money spent to calculate the perfect way to diet and minimize hunger and still feel somewhat satisfied. People say, “I'm dieting and I'm dieing.”
Bear with me. I know it's boring. I've avoiding talking about the details. It'll be over soon, and back to survival. You need to understand it, since it affects your goals in wilderness survival.
Yeehaw biochemistry yeah! The adaptation cycle goes something like this. Stored calories exist in our body in two main forms, glycogen and fat. Gycogen is stored in the liver or it is stored in the muscle. Fat is stored in the abdomen, but also in other places as more calories are taken in than can be used. If intake is less than 1500 calories, then the body goes “What a minute, what gives?” Sugar levels in the blood drop. We get tired. Our stomach circulates a variety of acids and enzymes in the stomach. The gurgling sound is the injection of enzymes from the duodenum to digest food. The whole body cycles chemicals to the digestive system based on routine eating times. Some blood is shunted there for some digestion. We feel tired some more. Most of the digestion happens at night while the rest of body shuts down. A good thing, because if it didn't, we would drag around with far less blood volume pumping around to muscles.
Some people say not to eat unless you can get 1500 calories. Well to be honest, that's considering a lost in the wilderness scenario, not a SHTF scenario. Really low caloric jump starts the drop in metabolic rate, and extends survivability some. This could give the edge, if you think help is on the way, but in our case, there is no help.
The brain needs sugar. It's the only food that the brain can use for energy. If the blood sugar drops, we get sleepy. It's that simple. The body says, “I'm tired, eat something dang it!” We get a response based on an empty stomach (it's not stretched and expanded) and the brain triggers a hunger mechanism. A classic diet trick is fill the stomach with water. It's stretched by the volume of liquid, and you feel less hungry. Sure.
If the body cannot get sugar, it will convert something to sugar, to maintain blood glucose. Glucose spiking too high works with the pancreas to release insulin. When starving, we've got the opposite problem that diabetics have.
The body locates the glycogen in the liver and muscle and through a boring complex process making sugar. The reason it stores it in muscle is availability. This minimizes the transfer of sugar in the most economical way possible. Long starvation creates very low blood sugar and ketoacidosis. It creates acetone breath that smell fruity, a warning sign that you'll already be all to aware of if there food. It is a very dangerous condition common in diabetics with very out of control blood sugar.
We're surviving in the woods. We're exercising more than normal. When the exertion is extended, the body sees this, and when the blood sugar drops, starts stealing from muscle glycogen. The hunger trigger goes off, enzymes and acids flow, and you think, “Wow I feel weak and hungry.”
Breaking down fat doesn't occur quickly. What happens is, as hunger extends over a progressively longer cycle, the body goes, “Wait a minute, the fires are burning too high.” It begins to lower basal metabolic rate. Your heart beat goes down, as does breathing. More and more energy intensive systems go into using lower amounts of energy. If water is an issue, and the body needs water for a ton of biochemical processes, that's an additional restriction. Therefore the body lowers metabolic rate even further. Keep it up, and you'll pass out or be listless.
Fat is a petty efficient storage unit for energy. It's twice as calorie rich, so more energy can be liberated. Thankfully for survival, by the time you start digesting fat, the metabolic rate is lower, and you're burning less normal calories. What this means is that the difficulty getting rid of fat, that you experience while dieting, will also help you maintain weight while getting less calories in the wilderness. It's a survival mechanism.
After a week of this, you feel pretty tired. Maybe you have headaches. Some people get a sense of well-being from exercise: the second wind that runners experience. Some of that is chemical, some of that is renewed confidence. It doesn't last. You are burning more calories than normal from activity. If you'd been burning fat, but still somewhat sedentary, then you'd be maintaining that weight. But you're not. You're burning more, eating less, and there are limits to the food sources.
In the woods, you're looking for calorie dense foods that you can gather as quickly as possible, using minimal energy for gathering and digestion. There's a very real reason that tribal people are not vegetarian. While some wild foods are rich in calories like nuts and some starches, most are not. Many of the items that you'll harvesting only can be harvested at certain times of the year. This isn't the grocery store. While there is an abundance of things to eat most of the time, it may not be in sources you're used to eating.
In winter, most people are sedentary based upon weather. You may not be. You're trying to keep your core temperature high. If you're outside in it, and looking for calories, you may very well be using much more than you could conceivably gain. Fishing from a pole or walking along with a throwing stick for a rabbit could expend a serious amount of calories, and put you into a deep caloric deficit.