Imagine a post apocalyptic world with fall out government, where there is not enough water to quench man's thirst and food to satiate his hunger.
Livestock was gone, the waters were infected by sorts of poisonous substances and there is too little vegetation to forage. Man had to survive, but the choices available to him are very limited. He needs energy to fight those zombies and A I.'s. Yes, the world was simultaneously invaded by zombies and A.I 's, the worst possible scenario. The A.I.'s became so smart that they've released an infectious substance from a military facility which led to a zombie outbreak. It became a three way tug of war between three races.
Man searching food
Man needs any edible food available. To fight, he needs to eat. Thankfully he saw something, a green grasshopper. Before the Apocalypse he had watched shows of tribes and other ethnic people treating critters like these as delicacies. He had no choice since the beginning. He caught the grasshopper, peels its wings and removes the spiky part of its legs. Without second thought he munches the critter. He can't taste it but he can feel a mixture of sliminess and crunchiness as he chews. And after that, he swallows it and searches for more.
We left man.
After n years we will come back to see him again. The question is, would he survive?
Removing the possibility that he would be killed and he have knowledge regarding poisonous critters, could he survive just by eating insects?
Before we look for man again let us first make a short research about what nutrients does his body needs and see if these critters can provide man with enough nutrients to survive. We are assuming here that no species (of insects) were wiped out during the invasion and he will not die searching for food.
Man and his bodily needs
Man needs food to stay alive. Here are his body's minimum nutrient requirements to do so.
Carbohydrates (Carbs)
The most essential nutrient in any disaster is the one that can sustain the functions of the body. The one that can give more calories, the better. Man needed energy to run, walk and jump. Carbohydrates would provide that. But how much carbohydrates does he need? The minimum recommended carbs per day is 130 grams.
Lactose, a dissacharide carbohydrate
Protein
Proteins are large complex molecules that is very important to man, only secondary to carbs. Proteins have five main functions: antibody, enzyme, messenger, as structural component and as a transport(or storage).
Myoglobin, a protein
As an antibody, proteins can repel foreign particles like bacteria and viruses. Proteins that act as enzymes perform by enhancing the chemical reactions in mans body. The speed of these chemical reactions is very important in sustaining life. The structural component proteins provides mobility to man while messenger proteins send signals to make sure that every part of the body will coordinate. Transport and storage proteins as their name suggests transfer and bind atoms and smaller molecules throughout the body. The minimum requirement for proteins is 0.8 grams of protein per kilogram of man per day.
Fats
Trimyristin
Together with Carbohydrates and proteins, fats are classified as one of the main macronutrients.
Hey 
You're half correct, they are all greasy because they are hydrophobes. They are soluble in organic solvents but insoluble in water. As for the difference you can think of it as this, oil is a kind of fat and fat is a kind of lipid.
Fats are very important because they help regulating temperature differences and other metabolic processes. They also contributed in structural development of the body. The minimum fat requirement per day is 0.5 gram per pound (weight of man).
Vitamins and Minerals
Both vitamins and minerals are considered as micronutrients. The main difference between the two is that Vitamins are organic and can be broken down by heat while minerals are inorganic, they tend to retain their elemental properties even in smaller levels.
A bottle of B-complex vitamins
Minerals are important because they aid in tooth and bone development, blood coagulation and muscle contraction. In the other hand vitamins helps in blood formation while keeping hair, eyes and skin healthy.
Different kinds of minerals in large quantities
Only some minerals are needed by the body (calcium, magnesium etc.) while all vitamins ( A, B complex, C etc.) are necessary.
Its quite tedious to write mans minimum nutrient requirements for vitamins and minerals (there's too many) but for our research's sake, we should do this. Vitamins can be classified as water-soluble or fat-soluble, it depends on how the body will dissolve it. Minerals can also be classified into two groups, this is based on the amounts the body needed. The classifications for minerals are Major Minerals and Trace minerals.
Vitamins
Vitamins (water soluble)
Vitamin C - 90 mg
Niacin - 1.6 mg
Thiamine - 1.2 mg
Riboflavin - 1.3 mg
Folate - 400 micrograms
Vitamin B-12 - 2.4 micrograms
Pantothenic acid - 5 micrograms
Vitamins (fat soluble)
Vitamin A - 900 mg
Vitamin E - 15 mg
Vitamin D - 15 micrograms
Vitamin K - 120 micrograms
Minerals
Major Minerals
Calcium - 1000 mg
Magnesium - 400 mg
Potassium - 4700 mg
Phosphorus - 700 mg
Sodium - 1500 mg
Chloride - 2300 mg
Trace Minerals
Chromium - 35 micrograms
Fluoride - 4 mg
Zinc - 11 mg
Iodine - 150 micrograms
Iron - 8 mg
Manganese - 2.3 mg
Copper - 900 micrograms
Molybdenum - 45 micrograms
Selenium - 55 micrograms
Water
Although water cannot be considered as nutrient we couldn't deny the fact that water is most important to man. Man needed to rehydrate because losing enough water could be fatal. In this situation we are assuming that man would never go dehydrated ( Here and there he would still be able to find clean water sources). So the only problem is food.
Could the insects satisfy his daily nutrient requirements to live? Let us see some insects nutritional content to find out.
Insects and Nutrients
Entomophagy comes from the Greek words éntomon and phagein which translates to 'to eat insects'. It is the study of humans use of insects as food.
We have found a very interesting data from FAO.org. Below are the nutritional value of some edible insects.
Fig.1
The green weaver ant can give an energy value of 1272kcal/100g. An average man needs at least 2500 kcal per day. That means ~200g of green weaver ants and the required energy for the day would be satisfied.
Insects are rich in protein. Take a look at Fig. 2.
Fig. 2
Based on this data, man would not have a deficit in protein. And we could also conclude that most insects are at least 13% protein.
Here is a comparison between insects and other animals protein content.
Fig. 3
An adult chapuline can give protein value that is almost double compared to other animal meats.
Man needs fats for metabolism and structural development, insects also have them.
Fig. 4
Saturated fatty acids (SFA) have high melting point. They are often found in tropical oils like palm and coconut oils. Unsaturated fatty acids (USFA) on the otherhand have lower melting points compared with their saturated counterpart. They are usually found in vegetable oil, nuts and seafoods. USFA are healthier to consume compared to SFA. Essential fatty acids cannot be synthesized by the body, it could only be obtained through diet. Omega 3 and Omega 6 fatty acids are examples of ESFA.
Edible insects are undeniably good sources of minerals especially iron and zinc. Below is the mineral values for mopane worm.
Fig. 5
Although most insects are not rich in chloride, molybdenum and selenium it can be easily obtained by other means. In the case of chloride it can be found in most edible salts.
Would you believe that these critters are also rich in vitamins?
Yes they are. Insects are extremely good source of Vitamins B complex, K and E. Low to Moderate source of Vitamin C. And although they are not very rich in Vitamin A it doesn't necessary mean that they don't have it. Man can just eat more(insects with Vitamin A) to satisfy this requirement.
We have the data needed. Let's visit man again. It has been n years.
There he is! He's eating a weevil larvae, well that's not very appetizing. He's OK but his skin looks like a little bit rough, maybe because he didn't found enough insects with Vitamins A and C. But all in all he's doing just fine.
Now we should leave him for good. Whatever happen to him, that's his fate to decide...
Conclusion
I know that we have an absurd example above but it can't change the fact that it's really possible(to survive by eating insects).
Actually in the 1970's many Cambodians were forced to eat crickets and spiders(not an insect) just to survived from the genocidal Khmer regime. As we know now this harsh experience of the Cambodians was integrated in their culture. That is why when you go to any streets there, most probably you would encounter stalls selling deep fried insects.
We can now say that with enough hydration, man can really survive just by eating insects (though they are not appetizing). Almost all the essential nutrients can be found in different species of insects. This is a very important issue to be addressed because the world's population is increasing every year. The developing countries are already experiencing food shortages. And studies are saying that insects as food might be one of the keys in solving this problem.
Thank you very much for reading!
Oh wait what's that!
That's another story folks...
Try reading What if insects are larger than us?
wikipedia.org/carbohydrates
wikipedia. org/protein
wikipedia. org/fat
wikipedia. org/vitamin
wikipedia. org/mineral
sfgate.com
diffen.com
nih.gov
fao.org
ALL IMAGES AND GIFS ARE FROM PUBLIC DOMAIN EXCEPT FOR THE TABLES
THE CREDITS FOR THE TABLES CAN BE SEEN AT THE BOTTOM OF THE TABLES THEMSELVES
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