Body Fat 101

Body fat is something we all have. It alters our appearance, health, warmth, and functioning. While we need body fat, excessive amounts can harm our health. If you wish to burn fat, you have come to the right place.

Body Fat 101 will teach you all about fat cells and ways you can reduce body fat.

States of Fat Burning/Retention

All bodies respond differently to food. Once consumed, your body absorbs nutrients which it stores as fat and converts into energy. Cells open receptors that take the nutrients they need to run, including fat cells.

Your body regularly burns fat through mobilization, transportation, and oxidation. Fatty acids release from fat cells and transport through the bloodstream to fuel cells. Adrenaline and noradrenaline are catecholamines that enhance fatty acid mobilization.


The fatty acids travel via the blood to reach the target cell. They bind to the serum protein albumin to move. Fatty acids oxidize and turn into adenosine triphosphate (ATP), or energy. The body breaks down primarily carbs and some fats to make ATP.


Anabolic and catabolic reactions are metabolic. Anabolic reactions contribute to growth and catabolic to producing and releasing energy. They occur continually and compose your metabolism. When looking to burn fat, you will want to maximize your catabolic reactions.

Your body prefers to use glucose for energy, followed by fats. Fat cells store triglycerides made of saturated fatty acids. Fatty acids are long carbon chains with hydrogen bonds.

During catabolism, the fatty acid breaks two carbons that turn into two-carbon acetyl sugar. This beta-oxidation reaction means fat breaks down like sugars. Since fatty acids have more carbons than glucose, they make more acetyl sugars.

Catabolizing triglycerides creates tons of acetyl sugars that flood the system and become keto acids (ketone bodies).

Ketone bodies form when the body quickly breaks down fat. When your body uses fats to create ATP, it requires more oxygen. When you run out of glucose to burn and switch to fat, you may have less energy due to your increased oxygen requirements.


Thermogenesis describes the calories burned to produce heat. Your body burns calories to digest food, so hard-to-digest meals create diet-induced thermogenesis. Thermogenesis can burn 5%-15% of what you eat.

High-protein foods have a thermic effect and require more energy to digest. Caffeine and polyphenols can also boost thermogenesis and help you release fatty acids.

Exercise can also trigger thermogenesis, called excess post-exercise oxygen consumption (EPOC). High-intensity exercises can burn more calories after a workout, which compounds when combined with a longer duration. If you do not have time, you could split your training into more sessions throughout the day to increase EPOC.

You can also induce thermogenesis by exposing yourself to cold temperatures.


Ketosis is a state where you use fat as the primary source of ATP. Since you minimize carbohydrates, your body produces more ketones for energy. Ketosis can help control blood sugar levels, maintain muscle mass, and reduce appetite.

When you stop eating carbohydrates, your body uses the remaining glycogen stores before switching to the keto acids produced from fat.

Why the Body Retains Fat Cells

Fat cells, or adipocytes, compose adipose tissue. You can find adipose tissue as subcutaneous fat between the skin and muscle or as visceral fat around the organs. Gaining weight expands the size of fat cells, which enlarges the adipose tissue.

The body retains fat cells for energy reserves when out of glycogen. Also, fat cells secrete chemicals to control appetite, protect vital organs and nerve tissue, insulate heat in the body, and regulate menstrual cycles.

Metabolism Effect on Fat Cells in the Body

Your metabolism controls how your body converts calories into energy. Anabolic and catabolic reactions oxidize calories to produce ATP, which helps with blood circulation, breathing, hormone levels, and cell repair.

The number of calories you burn to function without moving is your basal metabolic rate or metabolism.

Your metabolism depends on your biological sex, body composition, and age. Males usually have more muscle tissue than females, and people with more muscle burn more calories. Age often results in muscle loss and fat accumulation, which reduces the calories burned.

The number of calories burned depends on your basal metabolic rate, thermogenesis, physical activity, and nonexercise activity thermogenesis (NEAT).

Weight gain depends on your genetics, diet, thyroid, hormones, sleep, stress, physical activity, and environment. When you eat more calories than you burn, you store more triglycerides in your fat cells.

Having a higher metabolism, or burning more calories during the day, means you will have smaller fat cells than someone with a slower metabolism. However, burning more calories than you consume always results in weight loss, even if your body struggles to use energy.

HIIT vs. LISS for Fat Loss

High-intensity interval training (HIIT) can burn as many calories in less time than low-intensity steady-state (LISS), retain muscle mass, and continue burning calories after your workout. You can boost your aerobic endurance faster with HIIT than LISS as well.

LISS improves your aerobic endurance. You intake sufficient oxygen levels to provide energy to your muscles, so you need less recovery time. However, it burns fewer calories than HIIT. When on a strict deficit, LISS can burn calories without depleting your energy.

HIIT focuses on your anaerobic endurance. The high intensity means you cannot breathe as much, so your body relies on internal stores. You complete your workout in less time, but you need more recovery. HIIT helps you maintain muscle mass and burn fat, but it can harm you if you do not eat enough.

Effectiveness of Diets on Fat Loss

While the number of calories you eat has the strongest effect on weight loss, the kind of food still matters.

Reduced Calories

Reducing calories is the most effective way to lose weight. You consume less energy than normal while burning the same or more calories. Caloric restriction can reduce your risk for heart disease, stroke, and diabetes, but it lowers diet-induced thermogenesis.

Maintaining your caloric deficit sustains weight loss. By introducing more physical activity, you can preserve your bone density, aerobic capacity, and muscle mass.

However, what you eat can impact your performance, hunger, and overall health. Consuming a high-protein diet will reduce hunger levels, boost muscle performance and recovery, and increase thermogenesis.

It can have adverse effects on people with kidney disease. Also, a high-protein diet during middle age can increase mortality. The healthiest weight-loss diets include flexitarian, Weight Watchers, and vegan.


A ketogenic diet induces ketosis in your body. Your calories come from 5%-10% carbohydrates, 55%-60% fat, and 30%-35% protein, and it has shown short-term success in fat loss. As mentioned, the ketogenic diet forces your body to use fat as its primary energy source.

Short-term symptoms of the ketogenic diet come from the “keto flu,” where you experience headache, dizziness, nausea, insomnia, fatigue, and constipation. Long-term effects can include hypoproteinemia, hepatic steatosis, vitamin deficiencies, and kidney stones. When followed for extensive periods, it can increase total mortality.

By monitoring your electrolyte balance and supplementing with vitamins and minerals, you can healthfully follow the ketogenic diet.


The Mediterranean diet focuses on whole, plant-based foods, olive oil, and fish. By boosting the micronutrients consumed, the Mediterranean diet reduces heart disease, diabetes, and inflammation while encouraging a healthy weight.

However, it is easy to overeat if you do not engage in physical activity. While you can maintain weight loss, you will need to combine it with reduced calories to lose fat.

Since the meals are nutrient-dense and satiating, you can comfortably cut calories on the Mediterranean diet and experience no adverse health effects.