Your Fat Can Talk
Fat is the body’s way to store energy in a food shortage crisis. Our bodies contain two types of fat, visceral, white-yellow (white) and subcutaneous, brown. We unknowingly refer to what is known as white fat when referring to bulging physical body appearance. Fat cells have fat globules, iron containing mitochondria, the cell’s power producers that change energy into usable forms, and tiny blood vessels. The more mitochondria and blood vessels the more fat cells appear brown. Brown fat deposits are found mainly in the front and back of the neck and on the upper back. Brown fat gets depleted with age. Brown fat is present in mammals; including mice and human infants. Newborns have a higher brown fat content.
Fat tissue releases hormones and other substances that help regulate your body’s metabolism by communicating with other organs and tissues, such as your liver, pancreas, and muscles. Fat cells can communicate with other organs, with small pieces of genetic material, called microRNAs (ribonucleic acid) and transported in tiny, fluid-filled sacs called exosomes. These small membrane vesicles clean up a cell’s trash and they also carry signals to distant parts of the body, where they can impact multiple dimensions of cellular life. With age the level of microRNA processing enzyme called Dicer gets lower. Dr. C. Ronald Kahn of the Joslin Diabetes Center and Harvard Medical School and colleagues studied effect of dicer on brown and white fat. Animals missing the enzyme in their fat cells had less white fat than control mice. MicroRNAs circulating in the blood outside of exosomes were also lower in the mice lacking Dicer. Their studies revealed that fat tissue is the main source of circulating exosomal microRNAs in the body. The scientists next investigated whether microRNAs released by fat tissue could affect other tissues. These studies showed that circulating exosomal microRNAs from one mouse could regulate gene expression in the liver of another. These findings suggest that microRNAs made in fat tissue can regulate metabolism and gene expression throughout the body. Because fat is easily accessible, it might offer a way to deliver microRNAs to regulate genes in other organs.”
Fat of Choice
A third type of fat cells, identified as beige fat, has some characteristics of brown fat. Both beige and brown fat cells are able to burn calories, and could potentially serve as targets for therapies to try to reduce obesity. Dr. Shingo Kajimura at the University of California, San Francisco, found novel genes, namely, potassium channel K3 (KCNK3) and mitochondrial tumor suppressor 1 (MTUS1) required for beige fat cells to become brown fat cells and to burn energy to create heat.
1. Brown Fat
This fat is composed of several small lipid (fat) droplets and a large number of iron-containing mitochondria (the cell’s heat-burning engine). The iron, along with lots of blood tiny blood vessels, gives this fat its brownish appearance. Brown fat is usually found in the front and back of the neck and upper back. The purpose of brown fat is to burn calories in order to generate heat. That’s why brown fat is often referred to as the “good” fat, since it helps us burn, not store, calories. Brown fat is derived from muscle tissue and is found primarily in hibernating animals and newborns. After life as an infant, the quantity of brown fat significantly decreases. Adults who have comparatively higher brown fat levels tend to be younger, slender, and have normal blood sugar levels.
Increased brown fat development is activated by cold temperatures such as exercising outdoors in the wintertime or in a cold room, and lowering the temperature in your living and working spaces and exercising, which can convert white fat to a more metabolically active brown fat and getting enough high-quality sleep, aids proper melatonin production which influences the production of brown fat.. A team led by Dr. Francesco S. Celi of Virginia Commonwealth University and Dr. Paul Lee, now at the Garvan Institute of Medical Research in Australia reported that after a month of exposure to mild cold, the participants had a 42% increase in brown fat volume and a 10% increase in fat metabolic activity. These alterations completely reversed during the final month of warm exposure. All the changes occurred independently of seasonal change. Exercise can convert white fat to a more metabolically active brown fat. An excess of white fat around the belly region can be associated with a group of symptoms that signal an increased risk for heart disease, diabetes, and cancer.
Bottom line: You want as much of this type of fat as possible. Bring on the brown!
2. White Fat.
This type of fat is composed of a single lipid droplet and has far less mitochondria and blood vessels, thus resulting in its lighter white or yellow appearance. White fat is the predominant form of fat in the body, originating from connective tissue. White fat has many purposes. It provides the largest energy reserve in the body. It’s a thermal insulator and cushion for our internal organs, and cushions during external interactions with our environment (that’s code for a soft landing when we fall on our behind!). It is a major endocrine organ, producing one form of estrogen as well as leptin, a hormone that helps regulate appetite and hunger. White fat also has receptors for insulin, growth hormone, adrenaline, and cortisol (stress hormone). So, it’s a myth that fat cells just sit there and do nothing all day long!
White fat is found, oh heck, you know where it’s found. Just look in the mirror! In women, excess fat accumulates around the hips, thighs, buttocks, and breasts until perimenopause (the 40s), when fat is redistributed to the abdomen as well. Men tend to gather excess fat primarily in the belly region most of their lives. An excess of white fat inside the belly (visceral fat) is associated with metabolic syndrome—a group of symptoms that signal an increased risk for heart disease, diabetes, and cancer. Location of body fat really counts! Excess white fat throughout the body is associated with an increased risk of breast, colon, esophageal, gall bladder, and pancreatic cancer. It’s also associated with sleep apnea, and physical disabilities such as knee arthritis.
Here’s how much white fat a “normal-weight” person would carry throughout a lifetime: Men’s body fat range is 15 to 25 percent; women’s is 15 to 30 percent. Your generic 154-pound person would carry about 20 pounds of fat. One pound of stored fat contains roughly 4,000 calories, so 20 pounds has 80,000 calories of energy storage. If you required 2,000 calories to live per day, you’d last about 40 days on a desert island. These numbers aren’t meant to be perfect or exact, but instead, give you a broad, general idea.
You accumulate white fat by: consuming too many calories and expending too few calories.
Bottom line: As a species, white fat is very important to our survival. It’s a matter of how much and where it’s located. You want to control your visceral fat level (keeping your waist circumference to less than 35 inches if you’re a woman, and less than 40 inches if you’re a man) and keep your total body fat within the normal ranges for each gender.
Does white fat interact with brown fat? You better believe it. New research shows that when people overeat, they not only increase their total amount of white fat, but the overconsumption results in their brown fat becoming dysfunctional and thus unable to burn calories.
All right, the lesson is over, and now you’re locked and loaded with new knowledge about all things adipose tissue.