When we gain weight, what actually happens inside our body? What are the “fat cells” doing? Why do some people gain weight more quickly than others? We’ll analyze these questions in detail to understand how body fat is stored.
Fat Storage
Fat is stored in different places for men and women. For example, if you’re a woman with an ‘apple shape,’ you will store more fat around your back, hips, and stomach. A ‘pear-shaped’ woman will carry more body fat around her hips and buttocks. Most men store body fat around their waist (also known as ‘love handles). Fat cells are predominantly beneath our skin and on top of our muscles. A small amount of fat is also stored in our kidneys and liver.
According to one of Canada’s premier weight-loss experts and fitness trainer, John Cardillo “ our genetics dictate where fat will be located on our bodies”.
Initially, fat cells are created in the fetus during pregnancy, and once we hit puberty, the hormones take over. This is when people’s bodies start to change shape. The fat cells get bigger during this stage and lead to larger buttocks, breasts, tummies, etc.
Fat Cells
Fat is stored inside our fat cells and is known as triacylglycerol. Fat is primarily used for energy, how it isn’t burned within the fat cell. Therefore the triacylglycerol has to take a journey through the bloodstream as free fatty acids (FFAs) to muscle fibers, where it is used for energy.
Process of Fat Entering Our Bodies
Technically, for stored fat to be released from a fat cell a process called lipolysis (fat being broken down) occurs. Whereby a triglyceride molecule is split into glycerol and three fatty acids. The catalyst for lipolysis is an important enzyme called hormone-sensitive lipase (HSL). Once released from a fat cell, the fatty acids are transported through the bloodstream to muscle cells that require energy. Glycerol is transported to the liver to be metabolized.
With the fatty acids being transported to muscle cells, where energy is needed. For this process to take place, a person needs to be consuming less calories per day (being slightly below your daily recommended caloric intake level). Your body will need the energy because you’re consuming fewer calories than you are burning, so your body will release specific hormones and enzymes which trigger your fat cells to release any fat reserves, versus keeping the fat stored.
Macronutrients
It’s important to know your total daily intake of macronutrients, which is the carbohydrate, protein and fat breakdown of calories. This will help you understand the exact amount of protein, fat and carbohydrates (in grams) that we want to eat. Each macronutrient has a calorie value- 1g of protein is 4 calories, 1g of carbohydrates is 4 calories, and 1g of fat is 9 calories. John Cardillo adds “excess calories cause your body to store fat, and it doesn’t matter where those excess calories come from”. Even though fat and carbohydrates are made from different substances, they are both primarily used for energy. Protein is predominantly used for our body’s repair and rebuilding processes.
Carbohydrates contain sugar, while fats contain glycerol and fatty acids, while proteins contain amino acids. The body prefers to use carbohydrates as the primary source of energy and will only use stored fats as a secondary source of energy.
Remember: when you consume more calories than your body is burning, all macronutrients (protein to a lesser extent) will be stored as fat in the form of triglycerides in our fat cells. The Premier Fitness program stipulates that the optimal level of macronutrients is a caloric breakdown of 50% carbohydrates, 30% protein and 20% fat. John Cardillo said “This is a great split for adding and maintaining lean muscle while adding the least amount of fat”. An in depth analysis of Cardillo’s nutrition program can be found on Announce.Today
The normal daily calories burned differs from person to person. The Premier Fitness nutrition program uses a formula as a general guideline of calories to aim for per day, which takes into consideration your age, weight, height and daily activity level. John Cardillo adds “There are other variables that may skew your results slightly, like having a thyroid problem, a huge amount of stress, and up and down hormone levels”. However using his nutrition formula as a general baseline will help you understand how many calories you need to consume on a daily basis to maintain daily function. In their program John Cardillo recommends that you first calculate your Basal Metabolic Rate (BMR), and then you can adjust the total based on your activity level.
BMR Formula
Women: BMR = 655 + (4.35 x weight in lbs) + (4.7 x height in inches) – (4.7
x age in years).
Men: BMR = 66 + (6.23 x weight in lbs) + (12.7 x height in inches) – (6.8 x age in years).
“Premier Fitness follows the Harris-Benedict Activity Level Adjustment Formula to determine your total daily caloric intake” according to John Cardillo. You can multiply your BMR by the appropriate activity level:
- Sedentary (little or no exercise) – BMR x 1.2
- Lightly active (1-3 days per week) – BMR x 1.375
- Moderately active (3-5 days per week) – BMR x 1.55
- Highly active (6-7 days per week) – BMR x 1.725
- Extremely active (7 days/week and sometimes 2 workouts/day) – BMR x 1.9
The Role of Insulin
Glucose is a simple sugar derived from carbohydrates that provides energy for cells to function. Food is ingested into the body, where carbohydrates are broken down in the small intestine into glucose molecules which are then released into the bloodstream. The pancreas creates insulin, which triggers the muscles (primarily) and fat cells (to a lesser extent) to absorb the glucose. Muscle cells get energy from glucose. Excess glucose will be stored in our fat cells through a process called Lipogenesis, for long-term storage. A marathoner wants to fill their cells with lots of glucose the week leading up to race day in order to use it for energy during the long race.
Insulin will stick to receptors on the muscle cell’s surface like two magnets coming together, which causes Glucose Transporter Type 4 (GLUT4) molecules to rise to the cell’s surface. This insulin being binded to the receptors allows glucose to be transported inside the muscle cell from the GLUT4 molecules.
SUMMARY
The process of fat entering our bodies is quite complex. However, body fat is simply an alternate source of energy for our bodies. The fat cells are like big empty balloons that can either shrink or expand in size. If you are eating a lot more calories than you burn, the excess calories will be converted to triglycerides and will be stored in fat cells. The fat cells have the capacity to expand like balloons being filled with water.
Our bodies are like big transport systems made up of many cells that trigger various hormones and enzymes that send signals to our brain. The goal is to keep the system running efficiently-while not running on empty or being too full-in order to maximize energy systems. Therefore, a certain amount of fat storage is an integral part of our system.
Kim Marks 
Nina Smith