Identify some of the side effects of negative energy balance. which part of the brain signals when to start and stop eating? how do hunger and appetite differ? how can you approximate the number of calories required to keep you in energy balance? about percent of the calories you take in are used for physiological functions like breathing, blood circulation, and digestion.

Some of the side effects of negative energy balance are hunger, grumpiness, irritability, shakiness, cognitive fuzziness, anxiety, and low mood. Negative energy balance (which means you are spending more energy than you are consuming) is not a pleasant state, even just in the form of a delayed meal.  
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The part of the brain that signals when to start and stop eating is the hypothalamus. This part is responsible for the regulation of certain metabolic processes through the synthesizes of specific neurohormones, that are called to stimulate other specific hormones. The hypothalamus is responsible for the management of different body function such as body temperature, hunger,  fatigue, sleep, and circadian rhythms.
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Hunger and appetite are not synonymous, as they are totally different things: Hunger is the need for food. Appetite is the desire for food. In practice, they can work together: when you are hungry you may want to eat a slice of pizza, then your appetite makes you desire to eat another slice.
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it is possible to calculate the number of calories required to keep you in energy balance with a simple equation: Energy balance = energy input – energy output. in order to find out your energy input, you have to remember that protein and carbohydrate each provide 4 calories per gram, and fat provides 9 calories per gram, and then you have to count the number of calories you eat each day.
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About 60-75% percent of the calories you take in are used for physiological functions like breathing, blood circulation, and digestion. this component is called resting metabolic rate (RMR) and it is one of the three components of your metabolic rate, with physical activity and the thermic effect of food.

Where are the following