Do you know how you actually lose weight? Get to the bottom of the science behind burning body fat.

Obesity is a worldwide epidemic with a severe physical and emotional toll. According to research published by the National Library of Medicine in 2018, about 70 percent of American adults qualify as overweight or obese. The U.S. obesity rate of more than 36 percent places us 12th among nations with the highest obesity rates, according to the World Health Organization.

Individuals who are obese have a much higher risk of disabling chronic illnesses, lower quality of life, and impacted self-esteem and mental health. The WHO stresses the importance of maintaining a healthy weight to lower the risk for heart attack, stroke, osteoarthritis, and certain types of cancer.

If you fall into the obese or overweight category and want to lose weight, you're not alone. Unfortunately, empty promises from self-proclaimed “fitness experts” often downplay the hard work involved in a jaw-dropping transformation. For example, singer Adele recently debuted a completely new body after losing more than 100 pounds. Her trainer attributed the star's weight loss not to a miracle diet but to a true lifestyle change involving a healthy diet, weight training, and lots of cardio.

While losing weight can seem like an uphill battle (especially when you don't have Adele's resources), understanding the scientific factors that influence weight loss can help you achieve your goals. Let's take a deeper look at what actually happens when your body burns fat.

The Facts About Fat Storage

You probably already know that counting calories is the cornerstone of reducing your body mass. The body absorbs energy from the calories in the foods we eat—a process known as metabolism. When we consume more calories than our body needs to function, the excess becomes adipose tissue—more commonly called body fat. Technically, cells called lipids make up this loose connective tissue, which settles under the skin when we don't burn off surplus calories.

Scientists distinguish between many different types of body fat, including white, beige, and brown adipose tissue. Each type of tissue influences the internal health of our organs and systems.

Excess calories lead to the development of white adipose fat, which increases the risk of chronic metabolic diseases such as diabetes. You'll find this fat around the abdominal area, waist, and thighs. 

When white fat wraps around the belly and the internal organs within, doctors call it visceral fat. Excess visceral fat slows your metabolism and dramatically increases the risk for chronic illness, especially heart disease and type 2 diabetes. While scientists aren't sure why this type of fat impacts healthy organ function, they theorize that visceral fat releases proteins that inflame the body's tissues and narrow blood vessels, both of which contribute to damage to our organs and systems. In addition, visceral fat doesn't always have a visible impact on body mass because it's buried deep within the body. Too much of this type of fat can result in poor health outcomes even if your body mass index does not fall into the overweight or obese category.

By contrast, brown adipose tissue collects around the front and back of the torso, neck, and collarbone area. This type of fat actually burns calories to help keep us warm, so scientists think it may play a role in weight loss by lowering body fat and increasing the metabolic rate of energy burn.

Fun fact: While scientists once believed that only newborn babies had brown fat, more recent research indicates that we keep this type of adipose tissue throughout our lives.

The third type of adipose tissue, beige fat, gets its name because it derives from both brown and white fat cells. According to research published by Harvard Medical School, these tiny, pea-sized deposits along the spine and around the collarbone also burn calories and may have implications for treating obesity and diabetes. In fact, some studies suggest that good nutrition and regular exercise can help turn fat-storing white cells into fat-burning beige cells.

Burn, Baby, Burn: How We Really Get Rid of Body Fat

When we burn fat, we lose weight and become slimmer. Simple enough, right? But the process is actually a bit more complicated than that. The lipid cells in adipose tissue don't actually go anywhere when we lose body fat. The fat stored within these cells must travel through complicated physiological pathways. First, the lipid cells release the fat into the bloodstream in the form of free fatty acids (FFAs). The body then sends the FFAs to the tissues and cells that need energy.

When the FFAs reach the cells, each molecule splits into three separate fatty acids and a substance called glycerol. As muscles become active, the body delivers fatty acids to these areas, where it enters the mitochondria of the cells. The energy burn occurs here as FFAs convert to the necessary fuel for organ function and exercise.

Researchers from the Bulletin of the National Research Centre refer to the cells of the body as gas tanks for fat and energy. These cells expand with the introduction of excess calories and shrink as we convert fat to fuel for physical activity. The smaller fat cells account for the slimmer look when we lose weight, even though we actually aren't burning or losing anything. When the fat leaves the “gas tanks” empty, muscles become more visible.

We still haven't answered your number-one question: Where does the fat actually go? Believe it or not, we breathe and sweat it out. Think about how your respiration rate increases and your skin releases sweat when you keep up with your kids, jog around the block, or spend the day cleaning out your closets. Physical activity causes our muscles to cry out for FFAs, and we release what we don't need through sweat and the carbon dioxide we breathe out. Vigorous workouts that result in hard breathing, increased circulation, and buckets of sweat reflect the fat leaving our bodies, so you can look forward to the sculpted muscle tone that will remain. 

Fun fact: If you're dedicated to your morning espresso, we have good news—caffeine helps your body burn fat more efficiently. Scientists have found that caffeine consumption triggers increased neurotransmitter release. These brain chemicals, including dopamine, have an energizing effect that increases your metabolism. What’s more, the adrenalin triggered by caffeine consumption sends signals to your lipid cells, telling them to break down fat!

Lean Into the Science

Now that you understand how the fat loss process works, let's translate the scientific facts into a fitness method that works for your lifestyle. You'll need to know both your basal metabolic rate and your resting metabolic rate to take full advantage of the science behind weight loss. 

The basal metabolic rate is the minimum number of calories you use just to live. This category covers functions like cell production, the use of vitamins and nutrients, the circulation of blood and oxygen through the body, and breathing. The resting metabolic rate is slightly different and describes the calories your body uses at rest.

Your BMR and RMR are similar but not exactly the same. Pull out your calculator to figure out your BMR based on the Harris-Benedict formula:

• For men: 66 + (13.7 × weight in kg) + (5 × height in cm) – (6.8 × age in years)

• For women: 655 + (9.6 × weight in kg) + (1.8 × height in cm) – (4.7 × age in years)

Your BMR tells you how many calories you use just existing, depending on your respiration rate and other factors. With this number, you can use the “calories in, calories out” method to take the mystery out of weight loss. 

Let's say you're a 40-year-old woman who is 165 cm tall and weighs 68 kg (about 5’5” and 150 lbs.). Your formula would look like this:

655 + (9.6 × 68) + (1.8 × 165) – (4.7 × 40) = 655 + 652.8 + 297 - 188

With this example, you would have to consume fewer than 1417 calories per day to lose weight. If you eat more than that, burning calories through exercise can help you reduce the stored fat resulting from that surplus.

Whether your goal is to lose, gain, or maintain your weight, knowing the amount of energy you use at rest will help you understand the amount of energy you need from a healthy diet. While this formula offers an estimate of your BMR, an RMR test can more precisely determine how many calories you burn at rest. It also provides a picture of the ratio of fat to carbs you burn while at rest. To determine your RMR, the technician giving the test analyzes the carbon dioxide levels in your breath to see how much fat your body has expelled. Like BMI, RMR provides an estimate you can use to make healthy decisions. However, your results may vary depending on genetic makeup, body composition, and other factors.

Putting the Pieces Together

Weight optimization is far from a one-size-fits-all pursuit. However, nutrition experts from the National Institutes of Health generally recommend these steps to lose body fat and maintain a healthy weight:

• Calculate your BMR so you have a daily calorie target.

• Consume low-calorie, nutrient-rich foods such as green leafy vegetables, carrots, cauliflower, green beans, grapefruit, chicken breast, shrimp, fish, mushrooms, and tomatoes. This type of food consumption is associated with an increase in lean body mass.

• Count your calories each day and ensure they fall under your BMR.

• Enhance your body fat loss and burn more calories with exercises that increase your metabolic rate, such as high-intensity cardio, cycling, weight training, yoga, pilates, and swimming. As fat cells shrink, your lean body mass will become apparent.

Less Is Not Always More

Tracking your food consumption, body fat percentage, and metabolic rate as you become more fit can also help you detect when you’re not consuming enough calories - and when your body starts to go into starvation mode. This issue occurs when you lose weight and your body slows its metabolism in response, making it more difficult to shed pounds. When this occurs, many people ditch the diet and stop burning calories because they feel so discouraged about their slowed progress. Getting an updated RMR test can help you set new goals to get over the plateau caused by starvation mode.

Just as too much adipose tissue increases the risk of metabolic disease, too little body fat poses a health risk. When the level of adipose tissue declines, you may feel depleted and have little energy to exercise, work, or function. Optimize your weight and health, not to mention how well you feel, by balancing the calories you consume with the calories you crunch.

When you're ready to challenge yourself for better wellness and change your lifestyle, let Fitnescity do the math for you. By monitoring your body composition with DEXA scans, you can track your body fat level and ensure it remains in a healthy range for weight optimization. We can also test your resting metabolic rate so you have a starting point for your weight loss plan. Reach out today to find a convenient Fitnescity RMR testing location in your area.

References:

https://bnrc.springeropen.com/articles/10.1186/s42269-019-0238-z#ref-CR13

http://ncbi.nlm.nih.gov/pmc/articles/PMC6315740/

https://www.medicalnewstoday.com/articles/240989

https://www.webmd.com/diet/what-is-visceral-fat

https://www.healthline.com/health/what-is-basal-metabolic-rate

https://www.nia.nih.gov/health/maintaining-healthy-weight 

https://www.healthline.com/nutrition/coffee-increase-metabolism

https://ourworldindata.org/obesity 

https://hms.harvard.edu/news/beige-fat-cells-could-help-fight-obesity 

https://nypost.com/article/what-is-sirtfood-diet/

https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight

https://theconversation.com/brown-white-and-beige-understanding-your-bodys-different-fat-cells-could-help-with-weight-loss-138141