Making lifestyle changes, such as exercising regularly and cutting down on fattening food, is difficult enough when you're seeing results. However, if the pounds and inches don't seem to budge, you may start to wonder whether it's all really worth the trouble. Before you give up on your dream of building a better body, consider this: You may be one of the millions of people whose underactive metabolism has gone undiagnosed. This is very often the case even in individuals who have been told by their doctors that they have normal thyroid function based on blood test results. The routine thyroid tests are not sensitive enough to pick up every case of an under active thyroid. What's more, in many instances, slow metabolism is not due to thyroid dysfunction at all. Imbalance of the body's long-acting stress hormones, cortisol and DHEA (dehydroepiandrosterone), is the cause of many cases of sluggish metabolism. Excess levels of the sleep-inducing hormone, melatonin, can also be responsible for inefficient weight loss. The way that the stress hormones and melatonin slow the metabolic rate is by their influence on thyroid hormones.

The thyroid gland, located in the lower part of the neck, produces hormones referred to as T4 and T3. Hormones are messenger molecules that circulate throughout the body, regulating diverse bodily functions. T4, and the more powerful T3, regulate body temperature and the metabolic (biochemical reaction) rate of every cell in the body. When the level and/or activity of these hormones falls, the body temperature drops and the rate of chemical reactions slows throughout the body. Less energy is produced and more body fat accumulates. All things being equal, if thyroid hormone activity is lower, a fat loss program will be less successful.

So, how can you tell if you have a slow metabolism? We can take advantage of the intimate relationship between metabolic rate and body temperature. A simple, accurate way to gauge your metabolic rate is to measure your body temperature. For meaningful data, the following protocol must be followed:

1. Before going to bed, shake down an oral thermometer (below 95 degrees) and leave it within arm's reach of your bed.

2. First thing upon awakening in the morning, place the thermometer in your armpit and lay quietly in bed for 10 minutes before recording the reading. It is important to take the measurement while at rest, before getting out of bed in the morning. Repeat this procedure for 6 to 10 days.

3. Because the menstrual cycle causes fluctuations in body temperature, women who menstruate should start the measurements on the second or third day of their cycle. 

4. After collecting 6 to 10 days worth of temperatures, determine the average. If it is below 97.8 degrees Fahrenheit, you probably have an under active metabolism. The lower the temperature, the slower the metabolism.

After determining that your metabolic rate is slow, we need to try to uncover the cause so that it can be dealt with appropriately. Some doctors prescribe thyroid hormone replacement therapy based solely on a low body temperature. However, as previously mentioned, thyroid malfunction is only one possible cause of the problem. Imbalances of melatonin and of the stress hormones are other possible causes of low body temperature and low metabolic rate. To give thyroid replacement hormone when it is not needed will lead to eventual atrophy of the thyroid gland and to disruption of stress hormone production.

The most economical way to approach the investigation of an under active metabolism is to start by ruling out the phenomenon known as melatonin spillover; additional measurements of body temperature may be all that is needed to identify the cause of the problem. Have you ever noticed that you put on more weight in the winter? This is probably due, in part, to melatonin. Melatonin is a hormone that is produced by the pineal gland in the brain in response to darkness. Greater production of melatonin occurs in the winter because there are longer periods of darkness. Melatonin has a circadian (24 hour) rhythm or fluctuation in output, with greatest amounts being produced normally around 2:00 to 3:00 a.m. During sleep, body temperature usually drops about 1.1 to 1.2 degrees Celsius. With the temperature drop comes a decrease in metabolic rate of nearly 80 percent. Melatonin is responsible for about half of this nighttime drop in temperature and metabolism due to its effect of inhibiting thyroid hormone activity at the cell level. Normally, as morning approaches, melatonin levels fall and body temperature increases. However, some individuals produce excessive levels of melatonin well into the day. This is called melatonin spillover. When this occurs, body temperature and metabolic rate are lower than normal for long periods after getting up in the morning and, consequently, fewer calories are burned. To determine if you have melatonin spillover, you follow all of the previous instructions for measuring body temperature except for two differences: First, you open the blinds in your bedroom. Second, you wait 45 minutes, lying with eyes open, before measuring your temperature. If your temperature normalizes with this procedure, then melatonin spillover is the cause of your slow metabolism. The way this works is that melatonin production is suppressed when the retina of the eye is exposed to bright light. The bright light causes melatonin levels to decrease, and therefore body temperature and metabolic rate increase. Dim light is less effective in suppressing melatonin. People who spend their day indoors with insufficient lighting have higher daytime melatonin levels and therefore may have more difficulty losing weight. The treatment for melatonin spillover is to spend time on a daily basis within a certain distance of a bright light of specific intensity. For instance, if the light intensity is 2500 lux, it is necessary to be within six feet of it. You should not stare at the light, and it need not be full-spectrum, just strong! A company by the name of Northern Light Technologies sells a 10,000 lux desktop lamp. Their number is (800) 263-0066. When melatonin spillover is the cause of an under active metabolism, simply sitting in front of a special light can make the difference in losing body fat!

If melatonin spillover is determined not to be the cause of the slow metabolism, the next area to investigate is the output of adrenal stress hormones, cortisol and DHEA. These are best measured from saliva samples. Cortisol and DHEA are produced by the two adrenal or stress glands, which are situated above the kidneys. These hormones are secreted in a circadian fashion. In times of stress, the normal reaction of the body is to produce greater quantities of both cortisol and DHEA. When the stress ends, the body reduces its output of cortisol and DHEA to resting levels and everything is fine. This is what happens with short episodes of stress. However, when the stress is prolonged, the body prefers to make increasingly greater amounts of cortisol and less DHEA. How long does it take for this to occur? One study showed that after just 28 days of continuous stress, cortisol levels had climbed to 240 percent of starting values and DHEA had dropped to 15 percent of baseline levels! What's worse is that even after the stress is removed, the body sometimes does not recover and normalize output of these hormones, but instead, remains in the stress response mode with high cortisol and low DHEA output.

The consequences of elevated cortisol and reduced DHEA levels are damaging to all the body's systems. With regard to metabolism, an elevated cortisol to DHEA ratio can cause suppression via alteration of thyroid hormone function. In times of stress, the body attempts to conserve energy by slowing metabolism. What happens is that TSH and T3 levels fall (by as much as 30 percent) and reverse T3 levels increase. TSH (thyroid stimulating hormone) is the hormone secreted by the pituitary gland at the base of the brain. TSH causes the thyroid gland to manufacture and release the hormones T4 and T3, which are responsible for regulating metabolic rate throughout the body. Most of the body's T3 is produced outside the thyroid (primarily in the liver) by enzymatic modification of T4. An elevated cortisol to DHEA ratio causes an inhibition of T3 production from T4. Cortisol-DHEA imbalance results in reduced metabolic rate not only by suppressing production of active thyroid hormone, but also by spurring production of "counterfeit" thyroid hormone. Reverse T3 is slightly different in structure from normal T3. Reverse T3 poorly binds to the same receptor sites as T3 and fails to exert biologic activity. Binding of reverse T3 to receptor sites is like putting a right-handed glove on your left hand. Not only does reverse T3 fail to stimulate metabolism, but by blocking normal T3 attachment to receptor sites it results in a further suppression of metabolic rate.

The way to correct cortisol-DHEA induced thyroid dysfunction is to remove the precipitating stress and simultaneously use therapies that restore a normal stress-response mechanism. This will bring cortisol and DHEA back into normal range. Most people equate the word "stress" with mental/emotional strain. There are many other things that stress the body. Probably the two other most common types of stress are inflammation and fluctuation in blood sugar levels. Prolonged stress of any type produces the same result: cortisol elevation and DHEA suppression.

Meditation, tai chi, and aerobic exercise can minimize Mental/emotional stress. All of these methods have been proven to reduce cortisol levels. When cortisol levels are lowered, DHEA output begins to increase toward normal.

Inflammation in the body may be obvious, as in arthritis, or it may be hidden. It must be identified and dealt with appropriately, which usually includes therapeutic diet and nutritional supplement strategies. The most common cause of hidden inflammation is a bacterial infection of the stomach. By eradicating these bacteria with the appropriate medication, cortisol and DHEA begin to normalize.

When blood sugar fluctuations are stressing the body, dietary and nutritional supplement strategies are very important. Each meal should have approximately 1 gram of protein for every 2 grams of carbohydrate. Chromium, magnesium, and vanadium are a few of the nutrients that regulate blood sugar metabolism. These may be taken in supplement form.

The body's recovery from the stress response mode is often facilitated by supplementation of exogenous DHEA and other compounds that can help support the health of the adrenal glands and aid in cortisol reduction.

The best way to determine if cortisol-DHEA imbalance is the cause of a slow metabolic rate is to measure the circadian output of these hormones from four saliva samples taken at specific times over the course of one day. Saliva is a better test specimen than urine or blood for these hormones. This testing, and the appropriate treatment strategies, necessitates the involvement of an experienced healthcare professional.

If melatonin and cortisol/DHEA appear to be functioning normally, then the thyroid is probably the cause of the under active metabolism. (A fourth possibility is that a protein called neurotensin, which is produced by the brain in response to stress, is the culprit. There are presently no tests or therapies geared specifically toward neurotensin. However, neurotensin levels usually track cortisol output so no extra intervention may be necessary beyond those designed to rebalance cortisol and DHEA.) Thyroid dysfunction is best confirmed with a new saliva test. If T3 and T4, the active thyroid hormones, are found to be low, this is evidence of hypothyroidism (under active thyroid activity). A high TSH level also indicates hypothyroidism because if the thyroid is under active, the pituitary gland responds by producing more TSH in order to stimulate the sluggish thyroid. In many cases, the problem is not actually in the thyroid itself, but involves inadequate stimulation of the thyroid by an underactive pituitary (signified by low levels of TSH, T4 and T3), altered transport of thyroid hormone in the bloodstream, impaired conversion of T4 toT3, interference in binding of thyroid hormones to cell surface receptors, altered transport into the nucleus of the cell where thyroid hormones exert their action, or abnormal elimination of these hormones from the body.

Once an under active thyroid is diagnosed, the conventional treatment is prescription of thyroid replacement hormone. This is usually effective in restoring normal metabolic rate and, thus, improves weight loss.

Simply taking thyroid replacement hormone, however, fails to address the underlying cause of the malfunctioning thyroid. Many factors can interfere with the manufacture, release, transport, conversion, and elimination of thyroid hormones from the body. These include malnutrition, radiation exposure, illness, smoking, certain medications, exposure to various environmental pollutants, and even consumption of certain foods. A natural approach to reviving an under active thyroid (either alone or in conjunction with thyroid hormone replacement) needs to be multifaceted. 

Reduction in pollution exposure is critical. Using a quality water filter (I recommend Doulton brand) is one step in the right direction as pollutants and water additives, such as fluoride and chlorine, interfere with thyroid function. A comprehensive detoxification program, supervised by a qualified healthcare professional, can be effective in removing thyroid-suppressing toxins from the body. Detoxification involves following a special diet and using specific nutritional supplements, as well as other therapies such as sauna baths. 

Many foods have a negative effect on thyroid hormone synthesis, secretion, conversion, and elimination. These include: cabbage, Brussels sprouts, broccoli, turnips, mustard greens, peanuts, walnuts, almonds, sorghum, cassava, bamboo shoots, maize, mustard greens, onions, grapefruit, apples, millet, pinenuts, kale, and cauliflower. Individuals with an under active thyroid should reduce or eliminate these foods from their diet until thyroid function is normalized. Various nutrients need to be present for proper thyroid function. These include: iodine, selenium, glutathione, zinc, L-tyrosine, rubidium, copper, calcium, cobalt, and vitamins A, B2, B3, B6, C, D and E. Identification and correction of nutrient deficiencies are very important in supporting thyroid function. Last, but not least, moderate exercise helps to stimulate thyroid activity, as well.

To summarize, if body temperature testing reveals slow metabolism, investigation and correction of the cause involves:

1. Ruling out melatonin spillover by measuring body temperature while lying in sunlight with eyes open. Light therapy is the way to correct melatonin spillover.

2. Measuring cortisol-DHEA levels from saliva samples. These are normalized by appropriate stress reduction and nutrient supplementation, including DHEA.

3. Testing for an under active thyroid by testing the saliva for T3, T4, and TSH. Thyroid hormone replacement therapy and/or comprehensive, natural therapies can be used to re-establish normal thyroid function.