The Basics: What Is Metabolism
You might remember some of this from your high school biology days: metabolism is essentially the sum of all the metabolic processes in your body. Some of these processes you control, some you don’t.
All the calories you burn in a day is often referred to as your TDEE or Total Daily Energy Expenditure (or TEE: Total Energy Expenditure). One common mistake I see is people thinking that all of the things on the right (RMR/BMR, Exercise, TEF, NEAT) make up equal parts of your TDEE, however most of our TDEE comes from our BMR which is largely beyond our control.
As you see below, the energy required for your liver, brain, etc. are large parts of your BMR. People with larger livers and brains require a little more energy (aka calories) and therefor a slightly higher BMR. Your amount of muscle and fat mass also contributes to your BMR is so that IS one component of BMR that you are able to change slightly over time.
So the components of your metabolism you have greater control over or are more able to make an impact on are your physical exercise, NEAT and TEF.
- Physical Exercise – As you know, exercising burns calories! Aerobic activity burns many calories during exercise and you stop burning those calories soon after you stop. Strength training burns fewer calories during the sessions, but increases your calories burning in the hours afterward. It’s important to remember that although we can increase our metabolism by increasing exercise, studies show it’s really not by that much and we often compensate by burning less calories elsewhere. My advice: Exercise primarily for your health and wellbeing. Enjoy the extra calories burned as a bonus.
- NEAT – Non-Exercise Activity Thermogenesis. These are the calories you burn moving your body outside of physical exercise. These are things like walking and fidgeting. Often when we reduce calories, like when on a diet, NEAT decreases if you don’t deliberate aim to keep up your steps. My advice: Set a daily step target that feels good for you and prolongs your life, while adding subtly to your metabolism.
- TEF – Thermic Effect of Food. Digestion uses energy, aka burns calories. Protein and fiber having the greatest cost of digestion so increasing them in your diet can increase your metabolism. This is one of my favorite strategies for increasing metabolism because most people need more protein and fiber in their diets.
Think Backwards: Components For A Slow Metabolism
Often people feel stuck with a slow metabolism and like it’s a life sentence to not achieving the goals that they want. It’s helpful to think backwards and think about IF you wanted to slow your metabolism, what would you do? Then do the opposite! Things that will slow your metabolism:
- Not resistance training
- Having low muscle mass
- Not participating in aerobic exercise
- Having a low fiber diet
- Having a low protein diet
- Losing weight quickly
- Drinking too little water
What About Green Tea?
If green tea helps contribute to your overall water consumption, then it could slightly help metabolism. Coffee and green tea are fairly similar for these purposes and this meta-analysis sums it up nicely: “Green tea preparations appear to induce a small, statistically non-significant weight loss in overweight or obese adults. Because the amount of weight loss is small, it is not likely to be clinically important. Green tea had no significant effect on the maintenance of weight loss.” So if you like green tea, great. If not, you’re likely not missing out on any meaningful benefits.
What About Age?
A pretty groundbreaking study came out in 2021 that showed metabolism doesn’t actually decrease from ages 20-60. The reason we FEEL like our metabolism decreases and that gaining weight is easier is actually from decreases in physical activity and losses of muscle mass. That is good news! It means you don’t just have this uphill battle (until you’re over 60, then it’s approximately a 0.7% decrease per year) against metabolism, you have a battle against inactivity.
Takeaways
Metabolism has many components. Some you can control, some you can’t. You can control eating a high fiber & protein diet, exercising regularly (with both aerobic and strength training), staying hydrated and avoiding rapid/drastic weight loss. The biggest part of your metabolism (BMR) is beyond your control and your’s could be 10% higher or lower than your friends, but that likely won’t hold you back from achieving any goals that you are after!
Photos From: https://tdeecalculator.org/faq/ & https://ebook.ecog-obesity.eu/chapter-energy-expenditure-physical-activity/metabolic-mechanical-cost-sedentary-physical-activities-obese-children-adolescents/