Hunger, Satiety, and Appetite are Body Signals that try to tell us how much and when to eat
Hunger is a normal sensation (stomach growling, hunger pains), which tells us that it is time to eat again. It is partially controlled by: (1) the “hypothalamus” (discussed below), (2) blood sugar (serum glucose level), (3) how empty our stomach is, and (4) certain hormone levels (discussed below).
Satiety is the feeling of fullness and satisfaction. Stretch receptors in the stomach send signals to the brain that the stomach is filled. Increased blood sugar (glucose), the activity of the hypothalamus, and the presence of food in the intestines all contribute to satiety.
Appetite is a conditioned mental image desire or interest in food that we associate with the sight, smell, or thought of it. Inappropriate appetite can override natural hunger and satiety, as when overweight people continue to eat even after they are full and their blood sugar is high. Individuals with eating disorders can also have no appetite for food even though they are very hungry, such as in a stressful situation or during an illness.
Mental Images control the “stimulus / imagery / response” of hunger, satiety, and appetite. Part of the reason that people have problems with weight control and eating disorders is based on the incorrect mental images that they link to the underlying stimuli. Mental conditioning can significantly alter the way our body responds. This obviously applies to the voluntary decisions most people make every day to eat certain unhealthy foods or inappropriate quantities that have a negative impact on their health, self-image and happiness.
What is less obvious to most people is that our internalized mental images also unconsciously influence our powerful autonomic nervous system (as well as our energy level, respiration rate, temperature, metabolism, energy level, fat storage, immune system, ability to heal and fight disease, etc. See Psychoneuroimmunology).
Our body-signaling mental images are acquired over a lifetime from many good-and-bad sources. We now know that “rewarding” a child for eating their vegetables, by giving them a high-sugar dessert (like “mom’s apple pie”) just before bedtime is a VERY BAD MENTAL IMAGE. We now know that the 1992 U.S. FDA Food Pyramid recommendations for consumption of high-quantities of indiscriminate carbohydrates was a VERY BAD MENTAL IMAGE, which contributed significantly to the American morbid obesity epidemic, causing unnecessary suffering and premature death of many thousands of naive American individuals who listened to bad government recommendations, and even taught the flawed Food Pyramid to children.
The Good News is that mature, intelligent adults can take control of their bad mental images and replace them with superior ones. Joyful Aging offers significant scientific information to help you identify your flawed mental images about nutrition, and understand why they should be replaced, in order to improve your longevity, health and lifetime happiness.
The hypothalamus is part of our brain that influences of our “autonomic nervous system”, which controls most of our internal organs. The hypothalamus releases hormones that help control the “endocrine” and nervous systems, regulate body temperature, metabolism and sleep, and affect many other body functions.
The Greek word “hormon” means "to urge or excite." Hormones play important roles in many basic human motivations and behavioral responses. Hormones serve as invaluable messengers, governors of growth, development, weight, and regulators of heart rate, respiration, temperature and various metabolic processes.
A healthy hypothalamus produces a hormone called “thyrotropin-releasing hormone” (TRH), which stimulates the “pituitary gland” to produce “thyroid-stimulating hormone” (TSH). TSH regulates the amount of “thyroid hormone” (TH) in the bloodstream.
Iodine is common in the sea, but rare on land. Iodine an essential element of TH. A person (or an entire country) that lacks an understanding of the important role of small amounts of iodine can develop “hypothyroidism” - fatigue, apathy, etc. For many American’s, their primary source of essential iodine is salt (sea salt or as an additive to common table salt). Zero salt diets may be deficient in essential iodine.
One important function of TH is helping the body convert food into energy and heat. TH exists in two major forms: “Levothyroxine” (T4, with four iodine atoms per molecule) is the inactive form of TH that can be converted into “Triiodothyronine” (T3), which is produced by a healthy thyroid gland.
T3 directly boosts energy metabolism in “mitochondria”, (the powerhouse chemical factories inside our cells). T3 triggers rapid protein synthesis and influences mitochondrial gene transcriptions, (the reading of genes and the synthesis of body-building proteins from our inherited genetic blueprint). These activities also cause the breakdown of protein amino acids, and an increase in free essential fatty acids. TH elevates the heart rate to meet the increased metabolic oxygen requirement.
TH also regulates body temperature. TSH, which stimulates the thyroid to produce TH, also stimulates “brown adipose tissue”, a mitochondria-rich tissue, to boost heat production in mammals without muscle activity.
TH fluctuates in response to caloric intake and external temperature. During starvation, the body naturally lowers TH, which not only to reduces caloric consumption, but also prevents ketone bodies from building up in the blood and damaging the kidneys and other organs (which can also happen to diabetics).
Injury, illness and negative mental images can lower TH levels, which may improve after the patient is healed and the mental images improve.
TH is sensitive to the levels of other hormones besides TSH. For example, estrogen partially blocks the efficiency of TH, so women compensate by producing more TH than men. This may be why women have larger thyroids than men and are more prone to thyroid disease of all types (including iodine deficiency, hypothyroidism, fatigue, apathy, etc.). This may also be related in part to monthly and lifetime changes in estrogen levels, post-menopausal body temperature changes, etc.
Women who take TH replacement pills must increase their TH dosage if they start taking birth control pills, to compensate for the resulting higher levels of estrogen.
Human growth hormone (HGH, which decreases with normal aging) partially blocks TH, but it also complements TH in its effects on growth, development, and metabolism. Indiscriminate self medication with over-the-counter products that influence natural hormone levels can be extremely dangerous.
TH plays a major role in metamorphosis, growth, development and weight in all vertebrates. TH affects development by binding to “thyroid hormone receptors: (TRs - molecules that then change their shape to an activated form). After being activated by TH, TRs can bind to responsive elements in the DNA, triggering gene transcription. The position of the TR attaching to the responsive element facilitates the copying of some genes, and blocks others from being copied.
TRs are nuclear receptors like: retinoid A receptors, Vitamin D receptors, and steroid hormone receptors. TRs change configuration when attached to T3, and this changed configuration allows them to attach to responsive elements in the genome. Nuclear receptors are often dimerized (attached to another nuclear receptor of the same or different type), but they remain inactive until bonded by the usual trigger. For example, thyroid hormone receptors dimerized with retinoid X receptors will not activate until they are bonded with T3 or retinoids (derivatives of Vitamin A).
Modern science still does not know all of the many genes that are regulated by TH. Some TR-responsive elements in the DNA are Alu elements, which are able to move around in the genome on occasion, creating even more Alu elements in the genome. This allows many different genes to come under the control of TH without the genes themselves mutating. Different species may have different genes under control of TH, especially these concerned with development. For instance, while most mammals show similar symptoms of hypothyroidism, dogs show the additional symptom of seizures. Most chemicals that cause hypothyroidism do not block thyroid receptors in the genes; they only block the efficiency or synthesis of TH. Hence most of our information about which genes are regulated by TH comes from studying genetic disorders in which the TRs are non-functional.
Through many complex biochemical processes, our mental images (and other voluntary and autonomic factors) significantly influence the release of extremely powerful hormones, etc. which control and regulate almost everything inside our bodies, our health, longevity, risk factors for unnecessary premature aging, and the quality of our life. Positive self-images (based on more-accurate scientific understanding of our physiology) can influence our autonomic nervous system’s regulatory mechanisms and can help us interpret and respond correctly to many complex basic body signals that help us regulate body weight and many other health factors.
Will power, breaking long-term bad habits, and taking control of our own healthy, happy future are within the grasp of everyone who is willing to STOP SAYING: “I know I shouldn’t eat (or do) this, but …”
Children’s mental images are influenced by imperfect parents, peers, teachers, profit-motivated commercial television advertisements, etc. The difference between naïve, immature children, and mature, intelligent adults, is the motivating desire to seek the truth, and having found it, to change bad habits and replace them with better ones, based on the best available information. Children seek immediate gratification. Intelligent adults understand the need to understand risk factors, and seek ways to predict the future consequences of today’s good-versus-bad habits.
Perhaps 30% to 40% of the difference in weight between individuals is due to heredity, which affects basal metabolic rate, appetite and satiety (feeling full), body fat distribution, and possibly the tendency to be active or inactive.
Basal Metabolic Rate (BMR) determines the pace at which your body uses energy, and therefore, it affects your total energy requirement. BMR is based on heredity, height, body composition, and age. A lower BMR makes it easier to gain weight. A person's BMR can change in response to certain conditions. For example, starvation or very low-calorie diets decrease a person's BMR. Overeating increases BMR, as do fever and severe physical stress, such as recovery from surgery or from extensive burns.
Hunger, satiety, and appetite are body signals that tell us how much to eat. These signals can be influenced by the environment or ignored for short periods of time. They are powerful drives, and trying to ignore them for a long period of time (such as a restrictive diet) can cause out-of-control people to become obsessed with food.
Your body tries to keep your weight within a specific range, called your “set point”. Your body seems to regulate your weight similar to the way it regulates your temperature, blood pressure, and blood sugar (serum glucose levels). Research has shown that your body will waste calories if you overeat and conserve calories if you undereat. Your set point range seems to be influenced by your genetic makeup, but your actual weight within that range is influenced by your lifestyle or environment.
Your set point adjusts to a new level when it is maintained over time and can be altered by overeating, exercise, some medications, and some brain conditions. There is also a psychological set point. For example, people who live with others who are overweight see themselves that way and are more likely to accept additional weight gain. Self image clearly plays a role in eating and exercise behavior.
Your weight distribution changes as you age. Aging leads to replacement of lean muscle mass with fat. Men store more fat in the abdomen as they age and women store more in the hips and thighs as they age. Repeated weight loss and gain can change the proportion of fat to lean tissue in your body and actually increase your percentage of body fat.
Food advertising and the accessibility of fast foods tempt us to eat large servings, often of starchy high-sugar and high-fat foods. In addition, many foods are presented as being better for you than they really are. For example, a low-fat cookie is still a high-carbohydrate fattening cookie with little useful nutrition. Potato chips labeled cholesterol-free are still high-fat, low-nutrient snack foods.
A balanced, healthy diet supplies your body's nutritional needs, satisfies your hunger, decreases cravings, and decreases your risk for some diseases (like colon cancer and osteoporosis). In addition, you will generally feel better, have more energy, and be less likely to gain too much weight if you eat a healthy diet.
People who eat regular meals tend to be closer to a weight that is good for them than people who eat on an irregular schedule. Planned meals with reasonable portions of healthy foods are usually more nutritious than meals grabbed on the go or at the last minute. Also, skipping meals may make it more likely that you will overeat at the next meal or eat a less-than-nutritious snack. Buffets and super sized value meals are NOT a bargain, in terms of your health and well being.
Our modern sedentary lifestyles require far less physical activity than lifestyles of 100 years ago, or even a few decades ago, when most people had jobs that required physical labor. We work at jobs that require us to sit all day, and then we eat too much and snack while we watch television at night. We have created many labor-saving devices, from washing machines to remote controls for the television. All this has led to less than 22% of the United States population getting adequate physical activity. 4 out of 5 Americans need a significant increase in daily vigorous exercise.
Physical activity is a very important way to prevent obesity and improve health. Regular exercise can improve blood cholesterol and triglyceride levels, reduce blood sugar, and improve other indicators of disease. If you are depressed, regular exercise can help lift your mood. It can also boost your self-image and self-esteem, while making you more attractive to others around you.
You can be physically fit even if you are obese. In a study of more than 25,000 volunteers, researchers at the Cooper Clinic found that a person's fitness level was a stronger predictor of death than body weight. Overweight men in this study who were physically fit had a lower death risk than men who were a healthy weight but were not physically fit.
Other factors can affect what and how much you eat and how much activity you get:
Self-esteem and body image are strongly linked. Dissatisfaction with your body decreases your self-esteem, which can make it even more difficult for you to lose weight.
Repeated failure at dieting can affect your self-esteem and make it even more difficult to adopt healthy behaviors.
Emotional stress or emotional illnesses, such as depression, can lead to overeating. Some people eat to calm themselves, to avoid dealing with unpleasant tasks or situations, or to dampen negative emotions. Interestingly, even stress eating may be somewhat internally regulated. A recent Yale University study showed that in stressful situations, women who had more of the hormone cortisol (an indicator of stress) in their saliva ate more high-fat foods, and women who had low levels of cortisol in their saliva did not eat high-fat foods.
Medical conditions (such as hormone imbalances) and certain medications (such as antihistamines, some medications used to treat depression, steroids, insulin, some pills used to treat type 2 diabetes, lithium, valproic acid, and phenothiazines) have been associated with weight gain.
Alcohol use is associated with greater abdominal fat.
The above factors also affect a child's weight, along with the following:
Mother who had gestational diabetes. Children born to a woman who had gestational diabetes during pregnancy have a greater risk for becoming overweight and for developing diabetes.
Unwillingness to eat foods that they don't like. Children may be taught to prefer high-fat foods over vegetables, making a balanced diet difficult and weight gain more likely. They may also think that they don't like a food after having tried it only once or twice. In reality, it takes 8 to 10 times of being offered that same food before a preference is developed.
Family eating patterns or pressures, such as being required to finish all the food on the plate and obtaining sweet food rewards for behavior. When parents control the meal size or persuade a child to eat, the child does not learn to depend on his or her body signals (hunger, satiety, and appetite) for when and how much to eat.
Teens are also affected by peer pressure and the cultural influences that promote ultra-thinness. One study found that 59% of the teen girls were unhappy with their body shape, and 66% wanted to lose weight, yet only 29% of those studied were overweight. Magazine pictures influenced 69% of the girls’ idea of the perfect body shape, and 47% wanted to lose weight because of magazine pictures.
The more we know about “how” our mental images control who we are and what we will become, the more powerful and effective we will continue to become.
Joyful Aging offers many information resources to help accelerate the journey toward improved mental images.
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