Metabolism vs. Digestion
“My metabolism isn’t what it used to be.” “I could eat anything I wanted to when I was young, but I got older and my metabolism slowed down.”
In the fitness industry statements like these are heard often. However, it is often that the statement is not actually referring to metabolism but rather digestion, two different things that are commonly confused. Understanding how your body actually uses food can help you make thoughtful nutritional choices for a long and healthy life.
In a nutshell, metabolism refers to every single biochemical reaction happening inside your body in order to maintain life. For example, your body uses complex molecules from food in order to produce energy, whereas the digestive process involves breaking down the food that we eat and processing it so that it can be used by the body.
Let’s take Sarah, for example. She’s about to enjoy lunch at her desk. She packed a turkey sandwich with arugula, tomato, and cheese, all on a roll. The digestive process starts the moment she takes her first bite. As soon as that sweet bite hits her lips the chewing process is initiated. Her salivary glands begin producing saliva which contain amylase, an enzyme that helps to digest the roll from her sandwich.
When she swallows the food it travels down the esophagus and into her stomach. Contractions of her stomach cause the food to move around as her stomach releases hydrochloric acid. This and an enzyme called pepsin break the food down into a soft, almost liquid-like substance called chyme. Once soft enough the stomach releases the food into the first portion of her small intestine where it comes into contact with pancreatic juices, digestive enzymes, and bile. Her body is now releasing amylase, the same enzyme found in saliva, which again is necessary in the digestion of the roll; lipase which digests fats from the cheese; and protease which digests proteins from the turkey.
Once the food is thoroughly mixed, it travels into the second and third portions of the small intestine where additional nutrient absorption occurs. At this point, any part of the food that cannot be absorbed by the body passes through the ileum and into the first portion of the large intestine. Here her large intestine will absorb any water and solutes (i.e. fatty acids) and anything that cannot be absorbed will begin to concentrate in order to form stool.
Here’s where the digestive process gets…personal. The matter that cannot be used in the body is pushed through the large intestine, into the colon, and ultimately the stool will eventually be passed as feces, effectively ending the digestive process and leaving Sarah with an extra skip in her step.
It’s important to distinguish that the rate of one’s digestion varies from person to person and is dependent on factors like diet and activity level. Whereas, the speed of one’s digestion is measured by the complete transit time between when food enters the mouth until the time its excreted as feces. Of course, there are ways to speed up the rate of digestion. For example, consuming foods rich in fiber allow food to pass through the GI tract quickly, however high-fiber foods will not speed up one’s metabolism.
Metabolism, as mentioned previously, refers to every single biochemical reaction happening inside your body. There are two major categories of reactions: anabolic and catabolic. Catabolic reactions in the body are what cause things to be “broken down” so that they can later be absorbed and used. Anabolic reactions inside the body are essentially the rebuilding or converting of molecules into nutrients that the body needs.
Metabolism is responsible for creating the energy within your body. One measure of the energy is calories. It’s important to remember that when you regularly consume more calories than your body uses up the end result is weight gain. Alternatively, when your body uses up more calories than your body is taking in the end result is weight loss.
Both the digestive process and metabolism are heavily dependent on the food that we consume making it incredibly important that you stay mindful when making decisions about what to eat. Back in the 1950’s the term “junk food” was coined to refer to cheap or heavily processed foods that are high in calories from fat and sugar but have little to no fiber, protein, or minerals. It’s not “junk” simply because it doesn’t serve a purpose to your body, there’s also all the added preservatives inside junk food that your body is exposed to.
Your best bet is to consume a diet of nutrient-rich foods to give your body the best chance to get all of the vitamins, minerals, proteins, fats, and carbohydrates that it needs in order to function properly. Functions as basic as decision making, your mood, and of course, your energy level. Start by thinking about what you can add to your diet rather than what you should take away from it. Try adding more fruits and vegetables for a while and go from there; there’s no reason why eating healthier has to be negative.
Jessica Elsner is a certified personal trainer and co-owner of Foss Fitness ME, a boutique personal training studio located in South Portland. Foss Fitness ME specializes in improving the quality of life of Maine residents through our unique movement-based therapy programs and nutrition education. Whether you’re looking to lose weight, regain strength, or just feel like yourself again, our expert training and guidance will get you there. Please call us at 207-767-0890 to learn more about what we do and to set up a free consultation. Visit us on the web at: fossfitnessme.com. Foss Fitness ME is located at 936 Broadway in South Portland, ME 04106.