Nutrition is an immensely complicated thing. First, calories are a difficult unit by which to determine what type of foods, and the amounts of them that you should be eating.
This is the definition of a calorie: The quantity of thermal energy required to raise one gram of water 1°C at 15°C at 1 atmosphere.
It used to be obtained in controlled lab conditions at one atmosphere by burning a substance in pure oxygen, then measuring the amount of temperature change in a given amount of water.
Calories are quite simply, a measurement of heat energy. But nutrition involves so much more. Our body temperature is dependant on the calories generated as we metabolize food substances. When we move, or think, or breathe, we are using up some of that energy. But foods also contain nutrients that help us to rebuild dammaged bones and tissues, make it possible to move, to think, to digest substances, and a whole host of activities that our bodies require to keep working.
Our bodies are immensely complicated machines that use the various subtances in the foods we eat, along with water and oxygen to maintain the functionality of that machine, and produce work. To think of calories as a way of controlling weight is at best, primitive.
You asked if too few calories will make you feel fatigued. The answer is no. But too little water will, as will too much salt, too much sugar, too much caffein, to few vitamins, to few phyto-chemicles, too little exercize, too little sleep, too much sleep, and a host of other factors. Even such things as too little sunlight can contribute to feelings of lethargy, fatigue, and deppresion.
Nutrition needs to be ballaced, that is, a wide variety of foods must be eaten to make sure your body gets the many chemicals, minerals, and compounds it requires to provide energy, and the molecular building blocks to maintain itself and all of its functions. And it has been proven time and again that nutrients obtained from their natural food sources are much more effective at doing what they are supposed to do in the body than are the same substances obtained through pills, capsules, and suplements. There are intricate chemical processes involved that depend on other compounds found in the foods that aren't available in pills.
The advise given above about losing slowly is sound. And counting calories is a valuable tool in helping you to control protion sizes to a reasonable level. But behavioral modification is far more effective, and lasts a lifetime.
For instance, learn to eat slowly from a variety of foods. Eat small portions throughout the day rather than three big meals plus snacks. If you aren't hungry, don't eat. If you are eating due to emotional cues, learn to handle those emotions by working them out through exercise, or aritstic activities, or by resolving whatever is stressing you.
So learn about your foods, what they're made of, what theyr'e value is. And I hope you have great success.
Seeeeya; Goodweed of the North
