Medically reviewed by Neka Miller, PhD on August 15, 2021. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
People commonly talk about their metabolism as being slow or fast. Metabolism can be affected by a swath of factors related to your lifestyle, environment, and personal health. This can in turn affect your general health, weight gain, and energy throughout the day.
One of the most prominent components that affect your metabolism is your hormones. Certain hormones can inhibit your metabolism, while others can speed it up (some think coffee boosts your metabolism). Understanding your metabolic hormones may potentially help you maintain your overall health and help you better understand your results on a metabolism test. Learn more about the link between hormones and your metabolism below.
While many people associate metabolism with weight, your metabolism serves a more comprehensive purpose. Metabolism, in general, refers to the process wherein your body breaks down everything you drink and eat, converting the base components into usable fuel for all of the cells in your body.
During metabolism, calories taken from your food are combined with oxygen to release energy. Your body needs this energy all the time, even when you are at rest. Everything from breathing to blinking to growing entirely new cells requires energy. The number of calories that you burn to perform these basic functions is well known as your basal metabolic rate, which is what most people refer to as their metabolism. That basal metabolic rate is influenced by a wide range of things, including your body composition and age.
On top of your basal metabolic rate, your body burns even more calories based on thermogenesis and physical activity. Thermogenesis refers to the steps that go into food processing, including digestion, absorption of nutrients, transportation, and storage. About 10 percent of the calories that you burn go into thermogenesis. Physical activity accounts for the rest of the calories that you burn, and this is the most variable part of your metabolism as different forms of exercise burn a different number of calories.
On top of physical activity, experts have a separate category for the less deliberate exercise that you perform throughout the day. This is known as non-exercise activity thermogenesis (or NEAT). This includes small things like fidgeting, standing, or walking from your desk to the kitchen. On an average day, NEAT accounts for about 100 to 800 calories.
Weight gain is a surprisingly complex process. At its most basic, weight gain or loss comes down to your calories. Using more calories than you eat results in weight loss, while consuming more calories than you burn can result in weight gain. This is often where people bring metabolism into the equation.
Still, even that can be an oversimplification. While metabolism does play a role, your weight can be affected by a whole host of other factors, including hormones, genetics, your diet composition, and things in your environment that can influence your lifestyle, like stress, sleep, and exercise.
Hormones are a variety of chemicals produced by your body that serve a wide range of functions. Generally, balanced hormonal output ensures good health and proper bodily functions, including metabolism. Imbalances in certain hormones can potentially contribute to a slower metabolic rate. This leads many to question at what age does your metabolism slow down?
Insulin is a hormone produced by your pancreas. It essentially allows your cells to absorb blood sugar (blood glucose) and use it as energy or store it for later usage. The pancreas secretes small amounts of insulin throughout the day, and it increases production after meals. Insulin is also the main fat-storage hormone, allowing your body to store fat in fat cells.
However, some people may have insulin resistance in their body that does not respond to insulin as it normally should. This can result in high blood sugar, which can potentially progress to metabolic syndrome or prediabetes. Left untreated, prediabetes can eventually turn into type 2 diabetes and heighten your risk of cardiovascular disease and stroke.
Cortisol is the primary hormone released during stress. It triggers your natural fight-or-flight reaction, and in small amounts, this stress hormone is relatively harmless or even beneficial. However, chronic stress has quickly become a modern epidemic, resulting in a constant flood of cortisol. Those consistently high cortisol levels (which can be checked for with a cortisol test) can have significant physiological effects, including increased blood pressure and a suppressed immune system.
Unsurprisingly, high cortisol also affects metabolism. Experts believe that the stress hormone increases fat and carbohydrate metabolism, which then causes cravings for foods that are high in sugar, salt, and fat. Alternately, high cortisol levels may contribute to insulin resistance, causing your body to essentially hold more blood glucose. Cortisol may also signal the release of glucose from fat cells, which further increases blood sugar levels.
Leptin is a hormone produced by your fat cells. It is often referred to as the “satiety hormone” because it is responsible for signaling to your brain that your body is full, thus reducing your appetite and forcing you to stop eating.
In some people, the leptin system may not work as intended, resulting in leptin resistance. This can be caused by high insulin levels or inflammation in the hypothalamus. With leptin resistance, your brain never gets the signal to stop eating. Essentially, your brain thinks that you are constantly starving and encourages you to keep eating.
Ghrelin, known as the hunger hormone, is the counterpart to leptin. When your stomach is empty, or you don’t have enough calories, your body releases ghrelin, signaling to the hypothalamus that it’s time to get some grub. Ghrelin levels are typically highest right before a meal and lowest about an hour after eating.
However, some people have lower ghrelin levels when fasting, and after eating, ghrelin levels only decrease slightly. This then results in overeating.
Your thyroid gland is a butterfly-shaped gland that lies just in front of your windpipe. It is responsible for producing and secreting two hormones: triiodothyronine (T3) and thyroxine (T4). Together, these hormones regulate your metabolic rate, digestive functions, brain development, and bone maintenance. The production of thyroid gland hormones is controlled by the pituitary gland, which produces its own hormone called thyroid-stimulating hormone.
When your body doesn’t have enough thyroid hormones (hypothyroidism), you may experience weight gain as your body begins to store more fat than necessary. If you have too much thyroid hormone (hyperthyroidism), your body begins to rapidly break down fat cells. This can lead to unintended weight loss, an irregular heartbeat, and other health issues.
Testosterone is the main androgen hormone. Androgens are male sex hormones, but every gender has some testosterone, which plays a role in physical development and components of general health, like your metabolism.
Testosterone is essential to the production of muscle mass and the metabolism of fat. Abnormally low testosterone levels may potentially contribute to a higher proportion of fat mass. In women, elevated testosterone levels may also contribute to weight gain.
Metabolism is such a complex process that is influenced by several different mechanisms, like your hormones. If you’d like to dive deeper into understanding your body and its metabolism, consider the Everlywell Metabolism Test, which evaluates your cortisol, testosterone, and TSH levels.
1. Metabolism and weight loss: How you burn calories. Mayo Clinic. URL. Accessed August 15, 2021.
2. Blood Sugar & Other Hormones. University of California, San Francisco. URL. Accessed August 15, 2021.
3. Thyroid gland. Society for Endocrinology. URL. Accessed August 15, 2021.