Hormone Overview - Control of Metabolism
Hormones are chemical messengers. Each hormone is secreted by its specialized organ, then released into the blood stream. From there, hormone molecules are able to go to every cell in the body. They often interact not only with the surface of the cell, but can affect the DNA of each cell, the genetic code. They can tell your genes what to do.
There are a number of hormones at work in our bodies. Hormones regulate the use of fuel sources. They also direct a number of metabolic pathways.
Metabolism = Turning Food into Energy
When we need energy, our bodies have various fuel sources to choose from. If we have just eaten, we can use these nutrients (carbohydrate, fat, or protein) for energy. Muscle cells can use either glucose (sugar) or fatty acids (fat) for energy. Our brain usually relies on glucose and prefers a constant supply.
Much of the time, muscles rely on fat burning (fatty acid oxidation) for a steady energy supply. If we need a quick burst of energy, such as when we sprint up a hill, we burn mostly sugar (glucose). But this is quickly used up. Aerobic activity at a steady pace, like walking, will often use both fats and sugars as fuel.
strong>However, if your insulin levels are too high, your body remains in sugar-burning mode, and has difficulty tapping into fat stores – even if you have a lot of fat available! This makes it hard to lose weight, even if you are exercising or counting calories. You will need to follow certain strategies in order to tame insulin and become a fat-burner.
Although protein is primarily used to build muscle and to function as enzymes and signal molecules, it can be converted into glucose when needed. In times of stress or starvation, our bodies may use muscle protein for energy, even if we have plenty of fat reserves. This catabolism is often triggered by cortisol, the stress hormone.
Thyroid hormone (thyroxine) directs the rate of metabolism within each cell of the body. If your thyroid is not functioning properly, you may experience abnormalities in your energy level, mood, weight, and cholesterol level.
The master hormones insulin and glucagon control blood sugar levels. They determine whether the body is in fat-burning or fat-storing mode. For instance, when insulin levels are high, the body is unable to use fat stores for fuel. Hyperinsulinemia (chronically high insulin levels in the blood) must be overcome in order to lose weight and get healthy.
Insulin, along with leptin, CCK, ghrelin, NPY, PPY, and cortisol, have strong effects on the appetite control centers of the brain. These, in turn, affect many neurotransmitters such as serotonin, dopamine, and norepinephrine. Food, mood, and behaviors are closely interwined.
Hormones also influence the location of our fat. Even though our body shape is under genetic control, hormones and the type of diet we follow affect the amount of abdominal fat we have. The stress hormone cortisol seems to direct extra fat right to the midsection. Growth hormone and DHEA as well as testosterone promote lean muscularity.
Some hormones decrease with age and obesity
Many hormone levels decrease as we age. The production of sex hormones (estrogen, progesterone, and testosterone) decrease when the reproductive years are over. DHEA and growth hormone also wane, and some anti-aging doctors promote the use of supplemental sources of these as a “fountain of youth”.
Growth hormone and testosterone have strong muscle-building and fat-burning effects. But they may be in short supply if you are over 40 or are overweight. Aging and obesity both lead to reduced production of these hormones. Yet, there are ways to naturally promote higher levels of these powerful hormones with diet and lifestyle techniques.
In both women and men, fat cells produce estrogen, the female hormone. If we have a lot of fat, then our estrogen levels can be too high. Estrogen can fuel growth of breast and reproductive tract cancers in both men and women. In women, irregular periods and infertility may occur. In obese men, testosterone is converted to estrogen at a high rate. This problem can lead to fatigue, depression, erectile dysfunction, lack of libido, and a decrease in muscle size.
Insulin increases with age and body fat
Secretion of other hormones increases with age or with body fat. An overproduction of insulin, in particular, is a crucial factor in weight gain. High insulin levels cause or worsen many chronic degenerative diseases of our time – diseases like diabetes, heart disease, high blood pressure, stroke, cancer, and conditions like high cholesterol and arthritis. The list goes on and on.
As a woman enters the years prior to the onset of menopause, she may notice extra fat around the middle. The hormonal changes make her more likely to develop increased belly fat. Fat can also build up in the liver and other vital organs. This situation makes her more likely to develop insulin resistance.
As men age, they are likely to accumulate belly fat. With weight gain, they may become more insulin resistant. This condition is a set-up for heart disease and other cardiovascular problems.
Insulin resistance
Insulin resistance is a condition in which insulin can no longer usher glucose into the cells to be used as fuel. Even though insulin is present, even in elevated quantities, the cells don’t respond properly. They become resistant to insulin’s effects.
With insulin resistance, the body must compensate by increasing production of insulin. However, with chronically high levels of insulin in the blood, the cells develop even more resistance. And so a vicious cycle follows. Some highly resistant individuals may have insulin levels 10 – 20 times the normal range!
Insulin resistance occurs in men and women of all ages, but a tendency rises with the years. In the U.S., we are now seeing an increasing number of children with this serious problem due the country’s obesity epidemic and poor dietary habits.
Insulin resistance is associated with obesity and diabetes, but it often develops years before the individual becomes overweight. It’s never too early to develop healthy diet and exercise habits to prevent this severe health problem.
You can read ahead to learn how to tame insulin.
Hormone interaction
Many hormones interact with each other as well. Insulin and glucagon are hormones which control the same metabolic reactions but act in opposition to each other. Insulin stimulates fat storage while glucagon triggers fat burning enzymes. The ratio of insulin to glucagon blood levels is an important key. In order to lose weight, we need to learn how to turn up glucagon and at the same time lower insulin levels.
Insulin affects sex hormones and high insulin levels can be a factor in infertility. If you are faced with difficulty conceiving, you must lower insulin levels to increase your chances of success. Modest weight loss often leads to increased fertility and a better chance for a healthy pregnancy.
There are many hormones that have important roles in metabolism. Here is a summary of key hormones:
- Insulin – controls carbohydrate metabolism and fat storage.
- Glucagon – acts opposite to insulin, controls carbohydrate metabolism, increases fat burning.
- Thyroid – regulates metabolic rate at the cellular level.
- Cortisol – stress hormone, may affect metabolism and trigger an increase in appetite and the amount of abdominal fat we have. Read more.
- DHEA – a precursor to sex hormones, DHEA also tames the effects of cortisol and stimulates metabolism through its effects on other hormones.
- Sex hormones - testosterone, estrogen, progesterone – can effect muscle development, mood, and cellular function as well as reproduction. Menopause can be a time of weight gain and increased problems with insulin resistance. Men also seem to gain weight during mid-life.
- Leptin – produced by fat cells, leptin tells the brain “I’m full”. Read more.
- Growth Hormone(GH) – the hormone of youth, GH triggers muscle growth and fat burning. Read more.
- CCK – signals feelings of stomach fullness to the brain and turns off appetite
- Ghrelin – signals feelings of stomach emptiness, tells the brain “I’m hungry”. Read more.
- Adiponectin – produced by fat cells. High adiponectin levels seem to correlate with living longer.
- Calcitonin and PTH – These two hormones interact to control calcium levels in the blood and within cells. Calcium has a very important role as an intracellular messenger within the body. Lack of calcium may inhibit fat breakdown in fat cells and impair weight loss despite good efforts. Read more.
- PYY and NPY – These two hormones affect the appetite centers of the brain. When PYY is injected into rodents, they stop eating for hours. NPY acts to stimulate eating. Researchers are still trying to clarify the roles of these two brain chemicals. But certain foods may stimulate PYY, turning off appetite. Read more.
- Neurotransmitters – epinephrine, norepinephrine, serotonin, dopamine
- Epinephrine is stimulated by exercise or stress to burn fat and glucose in muscle cells
- Serotonin, norepinephrine, and dopamine affect appetite centers of the brain as well as mood, sleep, and energy levels. These neurotransmitters are targets of most anti-depressant medications. They are also affected by insulin and blood sugar levels, causing the food-mood response. Some of these medications may also affect appetite and trigger weight gain, although the response is variable between individuals.