The Science Behind Fat Metabolism
Every cell of the human body is involved in some sort of metabolism. We need metabolism to run intracellular processes and to keep each organ going at their optimal state. Proper metabolism involves the use of protein, carbohydrates, and lipids in our diet. Without these three components, fat metabolism cannot occur.
Our metabolism is controlled by the following mechanisms:
• The amount of exercise we do each day
• Our basal metabolic rate, which is defined by our size and our age
• The function of the thyroid gland, which puts out the hormones (T3 and T4), which turn on fat metabolism
• The uptake of glucose by the cells, which is controlled by insulin
• Our caloric intake
When we exercise, for example, we are training the heart to beat faster and stronger. We are also strengthening and adding to our muscle mass, especially if we undertake anaerobic exercises like weight lifting and machines that strengthen muscles. When we take in food from protein, carbohydrates, and healthy fats, these nutrients go to making muscle and fat is broken down, replaced by muscle mass. Often this does not mean a significant weight loss as muscle weighs more than fat; however, we will be leaner because muscle takes up less room in our bodies than fat.
If, on the other hand, we eat and do not exercise, the basal metabolic rate will determine how many calories we can eat per day before gaining weight. You can calculate your basal metabolic rate by using any one of the many basal body rate calculators available on the web.
Any calories we eat beyond that which is determined by our basal metabolic rate must be burned off through regular exercise or the body turns the nutrients into fat, which is stored in fat cells throughout the body. This is what is behind the “calories in and calories out formula” for weight loss, where a deficit needs to be created in order to lose weight.
The Role of the Thyroid Gland in Metabolism
The thyroid gland is a butterfly-shaped gland located in front of the larynx and windpipe in the neck. It produces vital hormones, thyroxine and triiodothyronine, which go to all the cells of the body and turn on cellular metabolism. Women, especially, are prone to low thyroid conditions, which cause cellular sluggishness and fatigue. Instead of using calories for metabolism, the metabolism of the cells decreases dramatically and calories from protein, carbohydrates, and fat in the diet are turned into fat, causing an increase in weight and an increase in the percentage of body weight that is made from fat.
Those people with hypothyroidism (a low thyroid condition) will have a slower heart rate, ongoing fatigue, dry skin, constipation and slowed body functions. Fat will accumulate in place of normal metabolic cellular functioning and weight loss is very difficult to accomplish.
The Role of Insulin in Fat Metabolism
Insulin is produced by the islet cells of the pancreas and is the hormone responsible for taking glucose from the bloodstream, turning it into cellular fuel. Type 2 diabetics and many people who are overweight suffer from some degree of insulin resistance. This means that glucose cannot enter the cells, even under high insulin conditions, and the cells are starved of the fuel necessary for metabolism. Glucose levels rise and, in order to bring the blood sugar level back down again, insulin must put the glucose somewhere.
The two places that insulin puts excess glucose are the liver and fat cells. In the liver, the glucose goes to make a storage-form of insulin called glycogen. When glycogen stores are full, the rest of the glucose goes to make fat. Obesity and insulin resistance can lead to having fatty liver and increased fat stores throughout the body. The goal of most medications that treat type 2 diabetes is to decrease insulin resistance so that more glucose from the diet goes to cellular metabolism and less to storage in fat cells.
Fat metabolism is complicated. It depends on having enough thyroid hormone to entice the cells to become involved in metabolism. It also depends on the ability of the body to recognize insulin as a means of putting glucose into the cells so that it can be utilized for cellular processes rather than stored as fat. As we become heavier with increased amounts of fat, this sets up a cycle of decreased physical activity, poor metabolism, and ever-increasing amounts of glucose stored as more fat within the fat cells of the body.