Fat, or ‘adipose tissue’ is made up of lipid (an oily substance)-filled cells called adipocytes. The denseness of this tissue depends on both the size and number of these cells. Once new fat are formed, because of a person’s increase in fat intake, they are permanent. They can be reduced in size, but not eliminated (except through liposuction, where they are physically removed from the body).
How do I Get Rid of Fat?
There are two chemical mechanisms for releasing fat from adipose tissue: lipolysis and thermogenesis.
Lipolysis involves the chemical decomposition of fat within adipose tissue and its movement into the blood as an energy source. Phosphatidylcholine, found in soy lecithin, can stimulate lipolysis.
Thermogenesis means increasing the metabolic rate by burning fat to produce body heat. Ephedrine, caffeine and aspirin stimulate the rate of thermogenesis. You can find a number of diet supplements containing ‘fat burner’ agents as the basis for their weight reduction claims.
Apples and Pears
Adipose tissue is stored differently in men and women. Generally, but not always, men’s adipose tissue is stored in the upper body. Women tend to store theirs in their lower bodies. You may hear the terms apple- and pear-shaped to describe this phenomenon.
Genetics plays a large part in this distribution. Children tend to have the same fat distribution as their same-sex parents. As we age, our bodies store fat differently. After menopause, women accumulate fat in their upper bodies. Extreme weight gain and “yo-yo dieting” can also increase upper body fat.
Surplus upper body fat is related to cardiovascular disease, hypertension, and non-insulin dependent diabetes. Older men store their fat in their lower bodies.
Why Do We Get Fat?
If you eat more energy (fats, carbohydrates and proteins) than you expend, it is converted into fat and stored in adipose tissue. This increases the density of the tissue. That is why, ideally, you should try to eat only as many calories as you use, and cut calories until you are doing this. You lose weight by eating less energy than you need and decreasing the amount of fat which is stored in your adipocytes.
You can also lose weight with a regular exercise program. The benefit of exercise during weight loss is that it preserves fat-free body mass and your fat loss will be equal or greater than your weight loss.
Different Types of Fat
Within the body are white and brown types of adipose tissue.
The white adipose tissue (WAT) found beneath the skin acts as a heat insulator in the body by conducting two-thirds less heat than other tissue. It surrounds internal organs and protects them from jarring. WAT is also found in the lymph nodes and the skeletal muscle. It stores triglycerides as energy for use as needed.
The number of white adipose cells and the amount of fat in a cell are regulated by various factors, including diet, physical activity, hormones and pregnancy.
In 1994, researchers discovered the hormone leptin in WAT. This meant that it was more than just a layer of fatty tissue beneath the skin. It was considered to be part of the endocrine system of organs, such as the thyroid, which secrete hormones that control many body functions. WAT secretes the hormones leptin, adiponectin and other proteins called adipokines, which are involved in fat metabolism, insulin sensitivity (affecting diabetes), vascular function and blood pressure regulation.
This is the key to the understanding of the underlying causes of obesity, which medical researchers refer to as a state of chronic mild inflammation. As WAT increases, adipokines (which have inflammatory properties) increases and adiponectin (which has anti-inflammatory properties) decreases. This increase may cause Type II diabetes, heart disease and cancers of the breast and colon in obesity.
Brown Adipose Tissue (BAT) gets its name from the rich blood vessels and densely packed mitochondria in it.
It is located near or around critical organs and supplies blood to the brain, spinal cord, heart, lungs, and kidneys during cold stress. In infants, BAT comprises 5% of the total body mass. BAT decreases in humans as they age and virtually disappears by adulthood.