How Does Weight Loss Work?

Some of the weight loss info out there can be pretty far-fetched. One of the best defenses while navigating through your own weight loss journey is going to be understanding the science behind HOW weight loss works so that you can distinguish the difference between breakthroughs and bullshit.

How do we store fat?

To understand how we burn fat, we first need to understand how we store fat. Body fat is stored in storage cells called adipocytes and used as energy when other forms of energy are not available. The number of these storage cells an individual has appears to be determined by early adolescence and rarely changes during adulthood. That means while we can’t get rid of our fat cells entirely, we can manipulate the size of these cells. 

Adipocytes can increase or decrease in size, like a balloon, depending on the amount of fat a body is storing. If you are not using as much energy as you are taking into your body, the excess will be stored as fat molecules (called triglycerides) within those adipocytes. This is what makes up your body fat. If this storage of excess body fat continues consistently over a long period of time, you will see weight gain happen.

How do we burn fat?

In order to burn that fat, the fat molecules must first be released from the storage system inside the fat storage cells. When the body needs to tap into this stored energy, certain hormones will trigger the release of fat molecules. These molecules are broken apart into smaller pieces called glycerol and free fatty acids.

Glycerol is primarily metabolized in the liver and kidneys where it is further broken down into the sugar molecule, glucose, and carbon dioxide. The glucose is used as energy by the body and the carbon dioxide is released from the body when you breathe out.

Free fatty acids continue through the body and are used in the liver and the muscles for energy by the body. As these fatty acids are oxidized by the body they produce water and carbon dioxide which is either secreted (through urine or sweat) or breathed out.

How Does Weight Loss Occur?

When most people start to look at losing weight, what they intend to do is lose fat mass. Weight loss can come from any loss of mass on the body including muscle mass, bone density, and fluid loss. But fat loss, more specifically, is reducing body fat while preserving or increasing lean body tissues such as muscle mass and bone density.

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As we discussed before, your fat cells expand with body fat when there is more energy being taken into the body than is being used. We take energy into our body through the diet in the form of calories and we expend energy through regular body processes and daily movement. So if we are eating more calories than we are using on a consistent basis, this is how we gain body weight.

The reverse of this is true for losing body weight. We must take in less calories than we are using on a consistent basis. This is called creating a caloric deficit. When you are in a caloric deficit, the body will signal the need to tap into your stored energy and trigger the release of those body fat molecules from your fat storage cells! 

It is important to note there is a difference between burning fat and fat loss. Burning fat, or fat molecules being metabolized by the body, is something that happens every day. But fat loss, or losing weight- specifically body fat mass is something that happens over time with a consistent caloric deficit in place.

How to Get in a Caloric Deficit

A caloric deficit simply means you are taking in less calories than you are using, on average, over time. To get into a caloric deficit, there are two parts of the equation we can look at: calories in and calories used.

One way to create a caloric deficit is to reduce the amount of calories you take in on average through what you eat. Keeping track of your calories and reducing portion sizes will help you to reduce the amount of calories you eat over time and create a caloric deficit. You only need to reduce your average daily calories by about 250-500 calories a day to create a substantial enough deficit to cause weight loss.

The other way to create a calorie deficit is to increase the amount of calories you use in a day. This can be increased through how much you move throughout the day and how much you exercise. Moving your body more will use more energy overtime and create a small caloric deficit.

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You’ll find that most weight loss programs encourage you to eat lower calorie foods and exercise more. This is the principle they are based on because all weight loss comes down to this basic theory of calories in and calories out!

Metabolism Considerations

While, yes, weight loss truly is as simple as creating a caloric deficit, something that sometimes gets overlooked are the metabolic considerations that go into determining a person’s basal metabolic rate (BMR). Your basal metabolic rate is the number of calories required to keep your body functioning at rest. It is often just referred to as your metabolism.

Even when you are at rest, your body needs energy for basic body processes such as breathing, and organ function. Your BMR is the number of calories your body uses to carry out these basic functions and cannot easily be changed the way diet and movement can be.

Individual factors that can affect your metabolism include:

• Your sex: men usually have less body fat and more muscle mass than women do of the same age and weight because of their natural testosterone levels. People with more muscle mass burn more calories at rest.

• Your body size: people who are larger and taller burn more calories at rest because the body needs more calories to support larger body functions.

• Your body composition: people with more muscle mass burn more calories at rest because muscles are more metabolically active than other body tissues are.

• Your age: as you get older, the amount of muscle mass you have tends to decrease which gradually slows down the amount of calories you burn at rest.

• Medical conditions: conditions such as Cushing's syndrome, hypo- or hyper- thyroidism, Hashimoto’s Disease, and diabetes can all have effects on how your resting metabolism works and how your body stores fat.

While it is important to acknowledge these individual differences in metabolism, the energy needs for the body’s basic functions do stay fairly consistent and are not easily changed. We cannot blame the metabolism for weight gain because the metabolism is a natural process that regulates many mechanisms to meet your individual needs.

Weight gain is a combination of all of these individual factors and a person’s environment, healthy habits, and lifestyle choices. Regardless of where your BMR is set, you still gain weight if you take in more calories than you burn, and you still lose weight if you burn more calories than you take in.

The Best Diet for Weight Loss

While you don’t have much control over your basal metabolic rate, you can control your energy balance.

You have control over how many calories you eat on average through your diet. Cutting calories from your diet doesn’t have to mean drastic changes to what you eat- it is actually best if you continue to eat foods you enjoy and focus more on portion control to reach your weight management goals. Simple tips like reducing your intake of caloric beverages (including alcohol) will help cut hundreds of calories from your diet without much effort.

You also have control over how many calories you burn by being more or less physically active. The more active you are, the more calories you burn. Physical activity can include routine movement like walking the dog, fidgeting, and doing house chores, as well as formal exercise such as jogging, or lifting weights (a bonus to lifting weights is if you increase the amount of muscle mass you have, you can slightly increase your BMR and burn more calories at rest!)

The key takeaway I want you to have from this is that there is no magic bullet. Don’t look to dietary supplements to burn fat - you know by this point in the article, that’s not how it works! Supplements that claim to “speed up your metabolism” are more hype than help and can have dangerous side effects that can hinder your weight loss progress.

The best diet for weight loss is one that puts you into a slight caloric deficit while considering your personal preferences for food and exercise.

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How Long Does it Really Take to Lose Weight?

Along with setting realistic expectations on how weight loss works, it is important to set realistic expectations for what a healthy weight loss rate is.

It is important to not lose weight too rapidly. Losing weight too quickly can increase your risk of gallstone formation, dehydration, malnutrition and have other major health detriments.

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A healthy weight loss rate is an average of 1% of your body weight per week, or about 0.5-3lbs a week. 

Also keep in mind that weight loss is not a linear process. Weight loss may occur quickly in the beginning of a program and then slow down. Additionally weight loss may occur faster some weeks and not at all other weeks.

Don’t be discouraged if your weight loss slows down or plateaus for a few days! As you’ve read today, the process of burning fat involves several metabolic processes and it takes time to do molecule-by-molecule! Put your patience pants on and keep going!

+References

1. Encyclopædia Britannica, inc. (n.d.). Adipose tissue. Encyclopædia Britannica. https://www.britannica.com/science/adipose-tissue.
2. Nature Publishing Group. (n.d.). Adipocyte numbers are set during childhood and tightly regulated in adults. Nature News. https://www.nature.com/articles/ncpgasthep1189.

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