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What does metabolism actually mean?

By Catherine Roy Oct 31, 2017 for

The word metabolism is thrown around quite a bit. But if we asked you to explain what it is and how it relates to your overall health, could you?

If not, don’t worry; you're not alone. That's why we're sharing the details you need to know about all things metabolism. And with some of our newest recommendations, InsideTracker can help you understand what the word really means, how it ties into your overall wellbeing, and how to optimize it.

So exactly what is metabolism?

In the simplest terms, your metabolism is the way your body utilizes calories from your diet to produce the energy it takes to keep all necessary bodily functions (breathing, digestion, etc) running seamlessly. Your metabolism regulates how many calories you need per day to accomplish these (and other) processes.

How efficiently your metabolism functions – aka your daily calorie burn – is determined by three factors: basal metabolic rate (BMR), thermic effect of food (TEF), and energy expenditure due to physical activity (EEPA). These three pieces affect how calories are used in the body. Together, they are known as our "total energy expenditure."

Basal Metabolic Rate: Consider this the number of calories your body needs to rest – and only rest. This means no sitting up, no talking, no use of any muscles. BMR accounts for anywhere between 60-70% of daily calorie intake, making it the largest contributor to overall metabolism. We all have different BMRs because it’s determined by a number of factors including age, gender, muscle mass, hormones, stress, physical fitness level, and nutritional state. Having a fast metabolism is usually associated with a high BMR.

Thermic Effect of Food: The digestion of food involves a lot of different processes. And although you don’t have to actively work to digest a meal, your body still uses up energy doing so. The cumulative amount of calories this burns makes up the thermic effect of food. On average, this accounts for approximately 10% of daily energy expenditure. Protein has the greatest effect, followed by carbohydrates, then fat.Energy

Expenditure from Physical Activity: These are the calories your body uses during movement. This accounts for roughly 20% of your daily calorie burn, but can vary depending on daily activities. It doesn’t just include the calories burned while working out, but also those burned while doing any physical movement, including the simplest movements like typing or folding laundry.

So, having a fast metabolism is usually associated with a high BMR, but how about those of us with “slow” metabolisms? Is it possible to increase the calories our bodies need, a.k.a. “boost” our metabolism? According to science, yes! Let us explain...

Biomarkers related to metabolism

Glucose is the body's primary source of energy. The body must regulate glucose levels in the blood to maintain good health.

Cholesterol is a waxy, fat-like substance that is made in the body by the liver and serves many vital functions. Normal cholesterol levels (HDL and LDL included) are important for maintaining energy, an active metabolism, and a healthy heart and circulatory system.

Triglycerides are a type of lipid found in your blood. When you eat, your body converts the calories it doesn’t immediately need into triglycerides. Then, between meals, hormones release triglycerides from storage to use for energy. Adequate levels of triglycerides are important for maintaining energy, improving metabolism, and promoting heart health.

Vitamin D is an important nutrient that helps the body absorb calcium, which helps to maintain bone strength and regulate the development and maintenance of the nervous system and skeletal muscle.

How to maintain a healthy metabolism

Use a standing desk:

Ever tried a standing desk? In multiple studies, those who used a standing desk for even just part of the work or school day had an increased energy expenditure compared tothose who remained seated all day.

Most standing desks are adjustable, meaning they can be used standing or sitting. So, if being on your feet all day seems a bit intimidating, start by alternating between sitting and standing and work your way up (literally)!

Drink green tea:

Green tea contains a specific compound that has been associated with an increase inenergy expenditure and fat burn.4,5 Although the effect is relatively small (and drinking green tea probably won’t solve all your metabolism woes), it will aid in supporting a healthy metabolism (bonus: it will also help you stay hydrated). Additionally, green tea is high in flavonols, which exert a strong antioxidant effect in the body.

Try swapping out one of your daily cups of coffee for green tea. Or, if you’re looking for that afternoon pick me up, grab an iced green tea and throw in some lemon for a flavor twist.

Prioritize your ZZZ’s:

It seems like a good night’s sleep is the solution for everything, and a healthy metabolism is no exception. Lack of sleep disrupts appetite hormones, increases caloric intake, and negatively alters glucose metabolism.5,6,7 Chronic, or even partial sleep deprivation is associated with an increased risk of obesity and diabetes.8

Aim to get 7-9 hours of sleep every night. Developing a nighttime routine - such as powering devices down an hour before bed and reading with a cup of tea can help you get those extra hours in.

Meet your daily protein goal:

Compared to carbohydrates and fat, protein has the highest thermic effect, meaning the body utilizes the highest amount of calories to digest and absorb it.9

Aim to include a complete protein source at every meal. For meat eaters, that can easily be done with eggs, chicken, fish, or lean beef. For plant-based eaters: tofu, tempeh, quinoa, and buckwheat are great options.

Add in High Intensity Interval Training workouts:

HIIT workouts increase post-exercise oxygen consumption, fat oxidation, and metabolic rate.10,11 Essentially, they keep the body burning fuel long after your workout is over (often known as the “after-burn” phenomenon).

High-intensity interval training includes 30-60 seconds of high intensity aerobic work followed by 1-4 minutes of rest or recovery, repeated for 4-10 rounds. Try to incorporate HIIT workouts three times per week on on nonconsecutive days. If you’re new to HIIT, check out the group fitness classes at your local gym; many of them are HIIT type workouts.

Optimizing your metabolism is no small feat, but armed with these recommendations and your blood data, you’ll be one step closer to reaching your overall health goal!


[1] Reiff C, Marlatt K, Dengel DR. “Difference in caloric expenditure in sitting versus standing desks.” J Phys Act Health. 2012 Sep;9(7):1009-11.[2] Roemmich JN. “Height-Adjustable Desks: Energy Expenditure, Liking, and Preference of Sitting and Standing.” J Phys Act Health. 2016 Oct;13(10):1094-1099.[3] Gibbs BB, Kowalsky RJ, Perdomo SJ, Grier M, Jakicic JM. “Energy expenditure of deskwork when sitting, standing or alternating positions.” Occup Med (Lond). 2017 Mar 1;67(2):121-127.[4] Hursel R, Viechtbauer W, Dulloo AG, Tremblay A, Tappy L, Rumpler W, Westerterp-Plantenga MS. “The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta-analysis.” Obes Rev. 2011 Jul;12(7):e573-81.[5] Markwald RR, Melanson EL, Smith MR, Higgins J, Perreault L, Eckel RH, Wright KP Jr. “Impact of insufficient sleep on total daily energy expenditure, food intake, and weight gain.” Proc Natl Acad Sci U S A. 2013 Apr 2;110(14):5695-700.[6] St-Onge MP, Roberts AL, Chen J, Kelleman M, O'Keeffe M, RoyChoudhury A, Jones PJ. “Short sleep duration increases energy intakes but does not change energy expenditure in normal-weight individuals.” Am J Clin Nutr. 2011 Aug;94(2):410-6.[7] Broussard JL, Kilkus JM, Delebecque F, Abraham V, Day A, Whitmore HR, Tasali E. “Elevated ghrelin predicts food intake during experimental sleep restriction.” Obesity (Silver Spring). 2016 Jan;24(1):132-8.[8] Sharma S, Kavuru M. “Sleep and Metabolism: An Overview.” Int J Endocrinol. 2010;2010. pii: 270832.[9] Pesta DH, Samuel VT. “A high-protein diet for reducing body fat: mechanisms and possible caveats.” Nutr Metab (Lond). 2014 Nov 19;11(1):53.[10] Chan HH, Burns SF. “Oxygen consumption, substrate oxidation, and blood pressure following sprint interval exercise.” Appl Physiol Nutr Metab. 2013 Feb;38(2):182-7.[11] Wingfield HL, Smith-Ryan AE, Melvin MN, Roelofs EJ, Trexler ET, Hackney AC, Weaver MA, Ryan ED. “The acute effect of exercise modality and nutrition manipulations on post-exercise resting energy expenditure and respiratory exchange ratio in women: a randomized trial.” Sports Med Open. 2015 Jun;2. pii: 11.

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