Put more simply, it's when you feel full and have no desire to continue eating. The mechanisms and events that lead to this state are numerous, quite complex and on the whole, poorly understood. This article will present several factors that lead to the consumption of too many calories, often sabotaging one's attempt at weight loss.

Goal
The mechanics involved with fat and weight loss are quite simple. If you eat less calories than you expend you lose weight. However, in order to reach or maintain your fat loss goals, your body and mind must have a sense of fullness and satisfaction from the foods and liquids that you consume.

If getting your desired body weight leaves you hungry and lethargic, the likelihood of long-term success is remote at best. If you can't live the lifestyle it took to get in shape, you won't be able to stay in shape.

Why do I get hungry?
At this time we should distinguish between hunger and appetite. Hunger is the true, physiological need for nourishment. Appetite, however, is simply the desire to eat, and has nothing to do with the need to eat. Why do we feel the need to eat?

There are two main reasons to eat. The physiological need is real hunger that signals that the body needs nourishment. The psychological desire for food is basically learned associations and habits that pertain to food and eating.

Problems and Possible Solutions

Internal cues to eat

1. Eat to survive
   Humans are designed to consume food and fluid until the nutritional needs of tissues and organs are fulfilled. However, this isn't our only trigger for satiety.
   If it were, our desire to eat would end immediately after consuming what we needed, rather than continuing to eat after we were full.
   
   Newborns up to six weeks old may be the only true depletion-driven eaters. They eat only the amount they need and only when they need it because they haven't yet had food-related experiences.
   
   Possible solution: To maintain current body weight and composition, the amount of calories we burn must match the calories we eat and absorb. In order to lose weight, we can't eat so little and burn so many calories that we are always hungry. We must arrive at the satiety level so that we comfortably stop eating.
   
   
2. Innate craving for sweetness
   Nearly all humans are born with a craving for sweetness. Newborns are a perfect example of this fact. Obviously, without learned eating behaviors, a newborn responds positively to sweetness and negatively to bitterness. These biases were probably at one time necessary for our species' survival. Bitterness tends to be correlated with toxins and sweetness with energy, favoring the bias for sweetness
   
   This innate human characteristic causes us to crave sweets even when we are not hungry. Unfortunately, food manufacturers prey upon this natural craving to lure customers into eating more than necessary. Every restaurant provides a dessert tray after a large meal and delicious, nutritionally useless foods are everywhere you look.
   
   Possible solution: Eat meals that contain a percentage of protein, fat, carbohydrates and fiber that makes you feel energetic and full. Eat them at least three to four times a day depending on your total allowed caloric intake.
   
   Each of these nutrients affects satiety in unique ways. Collectively, when consumed at each meal, they may initiate and prolong satiety better than if they were consumed alone. If you still want something sweet following a full meal, either satisfy the craving with a low-calorie dessert or just ignore it. Just because we feel the desire to eat something doesn't mean that the body needs it and we should eat it. The desire will usually subside about 30 minutes after the meal as the internal satiety cues are triggered and received by the brain. Dessert is a habit, and as such can be broken or replaced by a better habit.
   
   
3. Inherent set point
   Evidence is accumulating that genetics may influence the chances of an individual becoming fat or what body fat percentage they will settle into as an adult. This idea that genetics can influence adult body weight or fat is part of the set-point theory. This means that attempts to stray from this level of fatness or weight result in the body taking steps to bring the person back. This can be accomplished by several factors that have the effect of increasing food consumption, decreasing energy expenditure, or both.
   
   However, this is not to say that genetics are a death-sentence. Ultimately our lifestyles, such as our eating and exercise habits will determine what degree of influence our genetics have. Although your ancient ancestors may have had the same set point as you, it is unlikely that they reached it. Energy spent acquiring food and food preparation itself increased the energy cost of eating. Also, food was not as readily available as it is today, making chronic overfeeding unlikely. Today, we drive a car to the grocery store and buy prepared foods, reducing our energy cost of eating. Genes also get the opportunity to express themselves because of our sedentary lifestyles.
   
   Unless you are an ultra-endurance athlete, your daily activities pale in comparison to those of your ancestors. We are dealing with internal wiring made for a world where food was not plentiful or readily available and energy expenditure was high. Tiring of this we changed our environment. However, we have not been successful in changing our physiology. Our bodies have been designed to save for a rainy day, if you will. The problem is, in today's society, that rainy day does not come.
   
   Possible solution: Your current lifestyle dictates your current body. You must adhere to the principles of your fitness plan, which means making gradual changes and incorporating a realistic amount of work with realistic, convenient foods. Upon achievement of your goal, maintaining your body weight depends on whether or not you like the lifestyle you adopted to achieve it. At times, vanity and health can help defeat an appetite that would destroy the goal, but the bottom line remains the same…you must become addicted to your new lifestyle.

Learned eating cues
Following the newborn period, the child begins to have individual food experiences that will influence its eating behavior for life. These behaviors interact with our body's signals in order to control appetite and satiety. These learned cues are created in part by our parents, culture, commercial influences, etc. Keep in mind these are learned cues, and as such, they can be unlearned.

1. Social or ritual eating
   We often drink and eat when we are not truly hungry. Holiday feasting, going out after dinner for drinks with friends and consuming buttered popcorn throughout a movie are but a few examples of eating as a result of environmental influences instead of hunger.
   
   Possible solution: Eat a healthy snack before attending an event. People make bad food choices when they are hungry. Eating properly throughout the day will help you to make wiser food choices and maybe even bypass the ritual foods.
   
   
2. Habitual consumption
   Eating behaviors and patterns developed during youth, passed on to you by your parents or peers, will affect your choices throughout life. High-calorie foods and desserts after meals may not have been a problem during youth when energy expenditure was high, but now forced into less activity in order to make a living in adulthood, these behaviors lead to energy storage that will result in body fat. Ethnic groups mainly consuming foods indigenous to their culture for many generations develop a digestive physiology or enzymes that's compatible with the food they eat. Therefore, changing foods, if necessary, may be unpleasant until one's digestive tract adapts to the new food choices.
   
   Possible solution: Gradually incorporate changes into your current way of eating. Eat foods you like within your new adult caloric allotment.
   
   
3. Food - Mood
   Can your mood affect your appetite or more specifically, a craving for a particular food like chocolate? There has been a fair amount of research in the area of food, mood and appetite, but any conclusions drawn from this data have had little effect on our society's expanding waistline. No one has to be stuck with sinful food cravings for life.
   
   Ask a friend who has reached and maintained a fat loss goal. Often you will find that the baked potato dripping with butter, fast food hamburgers, sauces and milkshakes they used to enjoy, no longer taste good and may even be considered unappetizing. This is because they're addicted to healthy, lower-calorie, high-volume foods that allow them to look and feel great. This individual won't allow anything to interrupt this feeling. In other words, they unlearned these food-craving behaviors and replaced them with positive and beneficial eating habits.
   
   Possible Solution: Always try to make more good food choices than bad ones. But, you may incorporate some of your foods cravings into a healthy diet.

Summary
The level where regular satiety occurs will vary for each individual, influenced by their genetic predisposition and learned eating behaviors.

In today's environment, people often consume food or drink even though they're not hungry because of the social setting, type of food available or because of the habits they have learned.

Additionally, at some level, people aren't regularly satiated until they reach a certain body fat percentage or weight, then internal or physiological cues direct them to maintain that daily energy intake. This causes the body fat level to remain fairly constant.

This may take place at a low, moderate or high body fat percentage, depending on genetics. Learned behaviors may override this internal mechanism creating a weight control problem. Ultimately though, we are all responsible for what we eat, and what amount of movement we do in a day. Finding a balance of sensible choices and behaviors and enjoyment is the key to long-term success.