A Look at Metabolism

While everybody’s metabolism is unique and we all experience a progressive slowing, there is rarely an inherent and unavoidable root cause of poor metabolic health. Metabolically-related conditions are the world’s most common, and most deadly, health issues. These issues are almost entirely preventable (and even reversible) through lifestyle change (1). Metabolism is such a broad term that you may not even quite understand what this global health epidemic is, but Prime Meridian Healthcare™ is here to help.

What Is Metabolism?

You consume food which is processed within the body and turned into the fuel that is necessary for all physiological functions. The chemical reactions that occur within your cells to facilitate this continuous process is called “metabolism.” Countless metabolic functions are taking place at all times within your body, in an endless cycle that keeps every cell functioning; but that process is actually quite simple. After food is ingested, enzymes (proteins that facilitate chemical reactions) break down macronutrients into their smaller components: proteins into amino acids, fats into fatty acids, and carbohydrates into simple sugars so they can be used for the opposing (anabolic and catabolic) purposes of building up tissues or breaking them down.


Metabolic processes involving building and growing. In anabolic metabolic processes, the broken down components of the food we consume is used for the growth of new cells, the maintenance of existing cells, and the storage of fuel for future needs.


Metabolic processes involving breaking down for immediate use. Carbohydrates, fats, and (in some cases) proteins are broken down to fuel our biological functions and provide energy for our muscles to facilitate movement.

How much fuel your body needs to function (our metabolic rate) has three separate components: Basal Metabolism (BMR), Thermogenesis, and Physical Activity.

Basal Metabolism (BMR)

The amount of energy needed to maintain vital functions at rest. Anywhere from 50-80 percent of our metabolic needs are necessary to maintain vital organ function, maintain breathing, blood circulation, digestion, hormonal regulation, and other processes that you (seemingly) have little control of (2).


The process of obtaining and using fuel, requires fuel. Also known as the “thermic effect of food,” the process of digestion, absorption, transportation, and storage of the nutrients you get from food represents approximately 10 percent of your metabolic needs (3).

Physical Activity

Although weight management efforts are often focused on “burning calories,” the amount of energy to fuel daily movement actually represents a fairly small proportion of your metabolic needs. Although it can vary greatly, physical activity generally represents approximately 20 percent of our daily energy use (4).

Hormones and Metabolism


Hormones, those chemical messengers that regulate every physiological process, have vast influence over metabolism as well. The thyroid gland is the primary endocrine regulator of metabolism, but it doesn’t act alone (5). In order to maintain proper metabolic function, the thyroid releases hormones (T3 and T4) to speed up or slow down the various chemical reactions involved in metabolism. How active the thyroid is depends on the hypothalamus (the region of the brain that regulates homeostasis) and the pituitary gland (known as the “master gland” because of its influence over all hormone-secreting glands). When metabolic dysfunction is detected, the hypothalamus secretes thyroid releasing hormone (TRH) which in turn stimulates the pituitary gland to produce thyroid stimulating hormone (TSH), which induces the thyroid to release more thyroid hormones.

You’ve likely heard the hormone insulin associated with metabolism as well, and it is intricately involved. Insulin, which is secreted by the pancreas, is the chemical messenger tasked with regulating the storage of energy and it does so through a number of different biochemical pathways (6). Interestingly, insulin is both catabolic and anabolic. When consumed food is broken down into its usable parts, glucose (sugar) is released – most easily from carbohydrates, but also from fats and proteins – into the bloodstream and the pancreas secretes insulin to clear glucose that is not needed for immediate energy needs so that it can be stored as adipose (fat) to meet future energy needs. Insulin is anabolic in that it helps amino acids enter cells, promoting their growth (especially of muscle cells) (7).

The speed of our anabolic and catabolic metabolic processes is greatly determined by how much food we consume, and hormones influence this as well. In effort to maintain that internal balance (homeostasis), our body’s produce and secrete hormones that regulate our desire for fuel. Produced and secreted from our fat cells, leptin (the “satiety hormone”) communicates with the brain to regulate our energy balance; effectively, signaling to the brain that there is enough fuel for normal metabolic processes so that more food does not need to be consumed (8). Generally referred to as “the hunger hormone”, ghrelin is a signaling molecule produced in the gut that tells the brain that you do not have enough fuel to meet your metabolic demands and therefore should consume more and store more as fat (9). Leptin and ghrelin counterbalance each other to regulate how much you need to consume to maintain your basal metabolism.

Other hormones such as cortisol, estrogen, neuropeptide Y (NPY), and glucagon-like-peptide-1 (GLP-1) are also influential in regulating metabolism, appetite, and how much fat is stored.

Prime Meridian Healthcare is here to help you reverse the course of chronic disease, reduce your need for prescription drugs, and help you reclaim your health and quality of life, and that starts with education. Stay tuned to read about how all these metabolic factors influence your overall health and wellness.



Global Epidemic of Metabolic Syndrome

Saklayen M.


Energy Metabolism, Fuel Selection, and Body Weight

Galgani J. and Ravussin E.


Effect of Insulin on Human Skeletal Muscle

Fujita S., et al.


Energy Metabolism in Humans

Lam Y. and Ravussin E.


Thyroid Hormone Regulation of Metabolism

Mullur R., et al.


Role of Leptin in Human Physiology

Kelesidis T., et al.


Diet Induced Thermogenesis

Westerterp K.


Metabolic Actions of Insulin in Men and Women

Magkos F., et al.



Muller T., et al.