Why are carbohydrates and fats considered high energy foods

Usually, when you are short on energy, it's advisable to have glucose rich foods to replenish your energy quickly. Even bananas and a few fruits are often advised and prescribed by physicians to quicker recovery from fatigue-induced disorders. The reason such foods are preferred, when energy supplies are concerned, is they have plenty of carbohydrates and fats- the two most used and energy rich molecules. The reason behind this energy richness (3.75kcal/g for carbohydrates and almost 7.5kcal/g for fats) is their organic nature. Chemically, the C-H bonds which form these molecules are very stable and thus when broken liberate high amounts of energy which is dually utilized by the human system.

Carbohydrates are a good source of energy for the body. Carbohydrate is major nutrient which gets 50-60% of energy from carbs. Carbs are two types simple & complex. Simple is considered as high level of calories & energy but it is not healthy & advisable for all. Simple carbs should be limited.
Example for simple carbs are - simple carbohydrates foods are :Table sugar,Corn syrup,Fruit juice,Candy,Cake,Bread made with white flour
Pasta made with white flour,Soda pop,Candy,All baked goods made with white flour,Most packaged cereals
Honey,Milk,Yoghur,Jam,Chocolate,Biscuit & most of refined products.
Complex carbs are healthy carbs which means it is high in fibers, low in carbs(energy), contains good amount of b-vitamins & minerals that essentials for health. Example of complex carbs: Ragi, oats, whole wheat , fruits, vegetables, whole grains & lentil, etc.
But in 1 gm of carbs are 4 calories which is equal to protein.
Fat calories take only 20% but is high in calories , 1gm of fat contains 9 calories- it should be limited for all.
Thats why it is considered as high calories nutrients.