Brown is better than white. Let me hasten to add that I am not talking about skin color. My concern is what lies under the skin.
All fats are not equal
You are probably sick and tired of hearing about different types of fats. Omega-3, omega-6, poly-this, mono-that. Enough already.
But there are two types of fat you absolutely have to know about: brown fat and white fat.
White fat
Most of the fat stored by adults is the so-called white fat. The major function of this is to act as an energy storage system. One gram of fat has approximately 9 calories. So when your body needs energy, you can mobilize fat and get energy easily. Incidentally, proteins and carbohydrates each have 4 calories per gram.
White fat can pose dangers to your health. However, how dangerous white fat is depends on its location.
Fat thighs and buttocks?
These tend more to be cosmetic issues. The fat stored in these areas is usually not significantly harmful to the body as a whole.
These, of course, are the areas where a lot of women have deposits of fatty tissue, especially before menopause.
This fat has been shown to be genetically different from the fat stored in the belly. The genes active in the thigh fat are different from those active in belly fat. Hip and thigh fat does not appear to increase the risks of heart disease or diabetes.
Belly fat
This is a different kettle of fish altogether.
A study published in 2012 in the Journal of Clinical Endocrinology & Metabolism looked at some of the differences between fat located in the belly and that located on thighs and buttocks. The researchers studied stem cells from these two locations, and found differences in gene activity. Some of these genes help decide during development which part of the body goes where. And some of the genes determine how these fat cells respond to certain hormones, such as estrogen.
It appears that the location of fat: belly versus thighs, is preprogrammed.
And belly fat is a marker that the individual is at a higher risk of diabetes and heart disease. So if your belly is flat, but your hips and thighs are not, umm…be glad.
Subcutaneous fat
This is fat located just under the skin. It can be found in the thighs, buttocks, or even in the ‘abdomen,’ or the belly region. But this is not what we traditionally call ‘belly fat.’ People worry a lot about this kind of fat, because it is clearly visible, and it looks unsightly. It jiggles when we move, and we don’t like it. But it does not cause any significant health problems.
Visceral fat
This is where the problem lies. This is the ‘deep fat’ that we cannot see, also called ‘belly fat.’
It is called visceral fat because it surrounds the viscera, or the deep-situated organs of the body, especially in the belly.
Men tend to have more visceral fat than women, but after menopause, women start storing more of their fat in this location, thus raising their risk of major illnesses.
Secretory organ
Fatty tissue, especially white fat surrounding deep organs, is not just a store of energy. It secretes a lot of chemicals/hormones, which affect numerous body functions, such as sugar and fat metabolism, and even complex systems of immunity and reproduction.
Some of these hormones include leptin, cytokines, adipsin, angiotensinogen, etc. Fatty tissue also secretes steroid hormones.
It is felt that these secretions of the white fat contribute to illnesses such as type 2 diabetes, heart disease, high blood pressure, and perhaps even certain kinds of cancer.
What is brown fat?
This is a type of fat which is quite different from what we normally think of as fat. The main function of white fat has always been to store energy, which it does in the form of large droplets of fat. Of course, we now know that it also secretes some rather harmful hormones.
Brown fat, however, is designed to burn its fat stores and release energy in the form of heat. It contains much smaller fat droplets than white fat. Its color is the result of stores of iron present in the mitochondria, which are present in abundance in brown fat.
Where is the brown fat?
It turns out that this type of fat is present mostly in human infants in the shoulders and upper spine. This store is about 5% of the total weight of the infant, and is mainly there to keep the baby warm. Scientists used to think that adults did not have any brown fat. However, it is now felt that even adults have a little bit of brown fat in the neck and shoulders.
So what is the advantage?
Mice who have larger than usual stores of brown fat are more lean and healthy than regular mice. Interestingly, when these mice take in more calories, this brown fat burns more calories, thus avoiding obesity.
There is also some data in human beings that people with more brown fat have a lower body weight.
Turn white to brown
There is a transcription factor called Ppar γ which is involved in the specialization of both white and brown fat cells. Ppar is short for peroxisome proliferator-activated receptor. This is a type of protein which binds to a particular region in the DNA of a gene, and affects the development and metabolism of cells. However, there is a protein called Ebf2, or early B cell factor-2, which regulates the functioning of Ppar γ. This Ebf2 takes Ppar γ and directs it to binding sites on cells in such a way that a cell which is destined to become a fat cell is now ordered to become a brown fat cell.
Recruit brown fat
A Harvard research team has found that brown fat can be recruited in mice. Mice are apparently born with a present-from-birth, or ‘constitutive’ brown fat, and a so-called ‘recruitable’ brown fat. This kind of fat is found in the muscles, and also in areas of white fat.
There are some triggers which the brain responds to, and on receiving these signals, the brain can proceed with converting this ‘recruitable’ brown fat to actual brown fat, with significant health benefits.
Beige fat?
There is some suggestion that human beings exposed to cold can change some of their white fat to a type of fat which has some features of brown fat, the so-called ‘beige fat.’ There is considerable research interest in these newer developments, as they could impact the prevention and treatment of obesity and its complications.
Conclusion
- There is more to fat than meets the eye. In fact, the fat which does not meet the eye, the so-called belly fat or visceral fat, is more dangerous.
- An indicator that you have more belly fat than you need is a waist circumference of 35 inches or more in a woman and 40 inches or more in a man.
- Waist circumference needs to be measured just above the hip bone (pelvis).
- Also, brown fat is a specialized type of fat which may benefit us. Research is being conducted to see if we can convert white fat to brown or beige fat.