Your metabolism might seem like a mysterious force that controls your weight. Energy drinks, supplements, and diets often claim to speed up your metabolism. It can be common to hear people speak enviously about someone else’s fast metabolism. But even though people talk a lot about having a fast or slow metabolism, it’s rare to get any details on what that actually means.

In reality, metabolism is a general term that refers to a lot of processes inside your body that all work together to help you live and function. While some of what controls your metabolism is genetic, a lot of it is within your control, too. Read on to learn more about how your metabolism works, and how it can affect weight loss or weight gain.

1. Your Metabolism Controls More Than Your Weight

One common mistake people make about metabolism is believing it only refers to how quickly you gain weight or lose weight. In reality, your metabolism works to convert what you consume into the energy your body needs to function. Every cellular process inside your body is part of your metabolism. These chemical processes enable you to breathe, circulate blood, heal from injury, and more. Your body’s metabolism is working all the time, even when you’re asleep or resting. In fact, everything you do burns calories. Basic functions that your metabolism supports include:

• Breathing
• Pumping and circulating blood
• Growing new cells
• Healing from illness and repairing injuries
• Controlling hormone levels
• Digesting what you eat and drink

The amount of energy your body uses for basic functions like breathing is called your basal metabolic rate. The overall speed of your metabolism includes this basal rate, as well as the energy you use to digest food and the energy you burn doing physical activity and exercise. If your body uses fewer calories (less energy) when resting than someone else’s, you might say you have a slower metabolism than they do. This metabolic rate alone doesn’t determine your body size or your weight.

2. You Can Have Obesity and a Healthy Metabolism

Just because you’re living with obesity doesn’t necessarily mean you have a slow metabolism, or that there’s anything wrong with the way your body processes what you eat. Your body’s metabolism is partly controlled by your genes, but it also regulates itself to meet your needs. It may be working just fine, even if you aren’t happy with your body weight.

Your metabolism may change from day to day. Doing the same physical activity might burn more or fewer calories on a different day. Because your body adapts to different conditions where there might be more or less food available, it sends different signals about how much energy to burn depending on what time of the day it is, how often you’ve been eating or exercising, and other factors. So even if you feel like your metabolism is slower than it used to be, that doesn’t mean there’s anything wrong.

Obesity also doesn’t always overlap with metabolic disease. You can have a type of obesity called metabolically healthy obesity. In these cases, even if your BMI is in the obesity range, you don’t have any of the health issues that may occur with obesity, such as type 2 diabetes or prediabetes, high blood pressure, or liver disease.

Around half of all people with obesity can be considered metabolically healthy, if healthy is defined by the lack of metabolic syndrome. Metabolic syndrome means you have at least three metabolic abnormalities associated with obesity. These include high blood pressure, high cholesterol, excess abdominal fat, and insulin resistance.

3. Muscle Burns More Energy Than Fat

Someone with a faster metabolism burns more energy when they aren’t moving than someone with a slower metabolism. Even when you’re resting, a higher amount of muscle mass in your body will cause you to burn more energy, especially compared to fat. This is why strength training is a big part of almost any weight-loss physical activity plan. The more muscle you build, the easier it will be for you to lose weight.

According to Mayo Clinic, obesity risk may impact women differently than men, and muscle mass could be one reason why. Because men usually have more muscle mass than women, their bodies usually burn more calories more quickly.

This also helps explain why your metabolism might slow down as you age, since it can be common for people to lose muscle as they grow older.

4. Fasting and Extreme Dieting Can Hurt Your Metabolism

Your muscles’ ability to burn more calories is also why you may regain weight quickly after a crash diet. Fasting or dieting by not eating enough can cause your body to start breaking down muscle for energy. So when you stop dieting, your body has less muscle and burns energy more slowly than it did before, causing you to gain weight faster, even with fewer calories.

Extreme dieting, fasting, and skipping meals can also cause your metabolism to slow down. When you don’t eat enough to get what your body needs, your metabolism will adjust how much energy your body uses, trying to protect your body from starvation by slowing it down.

5. Simple Changes Can Help Your Metabolism

Some of the factors that control how your metabolism works are hard to change. But there are proven links between good metabolic function and two simple lifestyle choices: getting enough sleep and avoiding dehydration.

Sleep Deprivation Slows Your Metabolism

Getting enough sleep is very important for a healthy metabolism. When you aren’t sleeping enough, your hormones can be disrupted and slow down your metabolism. Studies have linked both insufficient sleep and poor sleep quality to higher rates of obesity and worse metabolic function.

Drinking Enough Water Is Important

Drinking enough water is linked to weight loss. It can help you feel full, eat less, and cut out extra calories from sugary drinks. Staying well-hydrated also helps your metabolism work properly.

Being dehydrated hurts your metabolism. Studies in both humans and animals show that drinking more water helps the body process nutrients and fat more efficiently, and that dehydration can lead to weight gain. And that’s not the only reason to drink enough water. Studies have also linked some hormones common in dehydration to heart disease, Alzheimer’s, cancer, and diabetes.

Talk to Your Healthcare Team

There’s a lot of misinformation about fast or slow metabolism. For that reason, it’s a good idea to talk to a doctor if you think there might be an issue with how your body is processing or using energy. Some diseases and disorders, such as Cushing’s syndrome or hypothyroidism, can cause issues with your metabolism. If your doctor or another healthcare provider suspects a thyroid issue, they may refer you to an endocrinologist, who can diagnose and help you address hormone issues related to obesity. Even if you don’t have a disease affecting your metabolism, your care team can still help you find healthy changes and habits that support how your metabolism works and help you reach a healthy weight.

Join the Conversation

On MyObesityTeam, people share their experiences with obesity, get advice, and find support from others who understand.

Do you think your metabolism is fast or slow? Let others know in the comments below.