It’s time to get a little more specific about what’s really going on when you have a slow metabolism. It’s not just some theoretical concept. Your metabolism is reflected in your major organ systems, and here are the five major players that affect how you store, burn and lose weight:
1. Your liver
If you were a car, your liver would be like the engine. It is vital and essential to keep you running. Over 600 known metabolic functions happen via the liver, and virtually every nutrient, every hormone, every chemical must be bio-transformed, or made active, by the liver. It’s your work horse.
Your liver creates bile, that powerful solution that breaks down fats and the nitrites and nitrates in your deli meats and bacon. Hormones get secreted from glands all over your body, but it is your liver that breaks down the hormones and makes them biologically active so they can go to work for you.
Your liver influences your electrolyte balance, swelling, dehydration, and water weight. It also acts like a filter for the blood coming through the digestive tract. It converts b-vitamins into coenzymes, and metabolizes nutrients such as proteins, fats, and carbohydrates.
Your liver also manufactures carnitine, which takes fat and escorts it to the mitochondria — your body’s little fat furnaces — in your cells, which influence 90% of your metabolic energy, or your metabolism. The faster and more efficiently you produce carnitine in your liver, the faster and more efficient your metabolism is.
The food you eat must feed your liver, rather than tax it. If you don’t feed your liver appropriately and frequently to stimulate its most efficient functioning, everything else will get disrupted. Because the liver is so closely linked with metabolism, it is one of the most crucial organs to pamper with your diet.
2. Your adrenals
Your adrenals are small glands that lie on top of your kidneys, and they secrete hormones that regulate your body’s response to stress. Your adrenals are responsible for the hormones that allow your body to adapt either functionally or dysfunctionally to changing situations. These hormones determine how you access fuel in your body, and what you do with the fuel or food you consume. Do you store it as fat? Or do you burn it as energy?
Some of the specific hormones the adrenals release include cortisol, adrenaline, and epinephrine. These are released in response to stress, which could be as major as a car accident or as minor as missing a meal. They respond to the acute stress of a disaster or the chronic stress of a bad relationship, an unpleasant work environment, or a taxing family situation.
The secretion of these stress hormones regulates the release of glucose or sugar from the muscle and liver cells, to either stimulate or slow down your body’s metabolic rate. That means this process is nutrient-dependent, or dependent on the food you do or don’t eat. If you nourish your body during times of stress with the right foods, you will not store as much as you burn. When you experience stress, the surge of hormones you experience will be influenced by what you’ve just been eating.
Adrenal exhaustion is a problem we see increasingly often in my clinic, caused by long-term stress and likely also by decreasing food quality and increasing environmental chemicals.
3. Your thyroid
The thyroid is a metabolic superstar! A butterfly-shaped gland located at the center of the throat, I think of the thyroid as your body’s furnace. The pituitary gland is like the thermostat, and the hypothalamus is like the guy controlling the thermostat, but the thyroid is the furnace and the hormones it produces, like T3 and T4, are the heat. When it gets too hot, the thermostat has to be turned down, and when it’s too cold, the thermostat gets cranked up. If any of these three mechanisms aren’t working just right, then the body’s temperature — a direct reflection of metabolism, or the rate at which the body is burning energy — will be off.
The thyroid performs this task via many functions in the body, including the extraction of iodine from food to produce T3 and T4. T3 and T4 travel through the bloodstream and influence the metabolism through the conversion of oxygen and calories to energy. This is what you want — an efficient furnace fueled by food and heating your house so it’s toasty and functional. T3, in particular, is the superhero of a fast metabolism. T3 possess approximately four times the metabolic hormone strength as T4.
But the thyroid has a dark side: a hormone called Reverse T3 (RT3), which is sort of like a misshaped thyroid hormone that isn’t very efficient in stimulating the metabolism, and in fact, blocks healthy T3 functioning. RT3 doesn’t mean to mess things up for you and your plans for those skinny jeans. It’s actually a smart response to prevent starvation. The problem is, when you diet, you know you aren’t starving, but your body doesn’t. In situations where you are experiencing chronic stress, certain disease processes, or nutritional deprivation, RT3 heeds your body’s “Red Alert!” cries, binding the T3 receptor sites and running interference so T3 can’t do its job. RT3 throws a big bucket of water on your metabolic fire, in a panicked effort to save your fat stores so you don’t die from what surely must be a catastrophic famine. The result is that your body quits burning and starts storing.
4. Your pituitary
I think of the pituitary gland as the conductor of the orchestra. It secretes hormones that regulate or conduct the actions of many other hormones in your body. For example, the pituitary stimulates the thyroid to secrete its hormones with thyroid-stimulating hormone, or TSH. If the TSH hormone level is high, that means the thyroid is requiring a lot of motivation or pushing to get its job done (hypothyroid).
If TSH is normal, all the pituitary has to do is speak in a normal voice: Keep up the good work. If TSH is very low, then the thyroid gland may be overactive (hyperthyroid), and the pituitary may only whisper. Of course, as I’ve explained earlier, if the thyroid is producing a lot of fat-storing RT3, the pituitary may perceive this as plenty of thyroid hormone, and may only whisper when it should be yelling. For this reason, a normal thyroid test isn’t necessarily indicative of optimal thyroid function.
5. Your substance
The final key player that directly influences the metabolism is your substance, which is how I refer to the fat and muscle in your body. The body stores the majority of your reserve fuel in either muscle or fat. Because muscle is constantly contracting, relaxing, beating, pushing, and pulling, it takes a lot of fuel to create and maintain it.
There are two types of fat in the body: white fat and brown fat. Brown fat is brown because it is rich in mitochondria, those little parts of the cell that burn fuel and produce energy. The more obese you are, the less brown fat and the more white fat you have. This is just another sick joke on your body, because brown fat burns fuel nine times faster than white fat. White fat is for long-term fat storage, and your body likes to make a Herculean effort to hold on to it.
White fat isn’t all bad. In fact, you need it. White fat is the fat under your skin and around your organs. It is designed to maintain body temperature, protect the organs, and act as an energy storage site for future need. White fat also secretes and regulates hormone output, and these hormones communicate directly with the adrenals, the pituitary, and the hypothalamus.
However, when your metabolism slows down, your body goes into super white-fat production mode, hoarding fat like some people hoard newspapers or shoes or junk mail or stray cats. You can literally be buried alive with all this saved energy, in the form of smothering white fat.
Brown fat is the thermogenic or furnace fat. It actually helps stimulate the metabolism by warming the body, increasing blood flow, and making it easier to deliver nutrients to the white fat. Brown fat helps regulate your cholesterol and triglycerides, transports waste to the intestines for elimination, synthesizes proteins, and stores and metabolizes fatty acids used for energy. Brown fat also metabolizes and stores carbohydrates, storing them as glucose for your red blood cells and brain.
These five major players are the keys to using food to sculpt your body the way you want it. Feeding your liver, soothing your adrenals, maximizing pituitary and thyroid function, and tweaking your fat balance are all part of a balance diet.
An Excerpt from #1 New York Times Best Selling Book, The Fast Metabolism Diet by Author and Nutritionist Haylie Pomroy.