Understanding Your Metabolism & Calculating Your Daily Caloric Needs
We all use the word “metabolism”, but do you actually know what it means and what influences it? Metabolism is often thrown under the bus and used as an excuse as to why we are not meeting our goals. I thought I would spend some time on the next couple of blog posts and do a deep dive into metabolism 101. We need to understand what we are working with here, and the many factors that can influence our daily needs.
Metabolism is defined as the biochemical processes that occur in a living organism. Metabolism Includes anabolism (the buildup of substances) and catabolism (the breakdown of substances). Most people think of metabolism specifically in regards to the breakdown of food and its conversion into energy, however, it is more than that.
Metabolism has 3 main roles:
- The aforementioned conversion of the energy in food, to the energy available to run the body’s cellular processes.
- The conversion of food into building blocks for lipids, proteins, and carbohydrates.
- The elimination of metabolic waste due to the body’s metabolic processes
Total Energy Expenditure
So now that you have metabolism basics down, do you understand what goes into determining your daily caloric needs to run those body processes? It’s called your TEE, or Total Energy Expenditure. It is typically true you need to be in a SMALL caloric deficit to lose fat, and while a calorie is a calorie (a unit of energy), the source of that calorie will ALWAYS be more important in my mind than the actual number. A calorie from kale is NOT going to behave the same way as a calorie from a Twinkie within your body. Food is information, and what kind of information are we feeding our bodies? This information affects everything including the hormones and enzymes we create, the bugs in our microbiome, and the energy produced at a cellular level.
Metabolism is the word that is often used to describe how many calories we burn in a day. Your metabolism impacts how your body processes “fuel”, both how fast and how much. The higher your metabolic rate, the more calories you burn, and the easier it is to lose weight and keep it off.
About 70% of the calories we require on a daily basis are used to just keep us alive, things like breathing and the functioning of our organs. This is called our Basal Metabolic Rate. The remaining approximately 20% of calories burned come from our physical activity and about 10% in digesting food.
BMR defined (basal metabolic rate): Calculator
What is BMR? Your BMR is a measurement of your body’s energy or the minimum level of calories your body needs when it’s resting. Things that can impact your BMR include:
- body weight
- fat-free mass: FFM comprises tissues such as skeletal muscle, heart, brain, liver, kidneys, and the GI tract organ.
- fat mass: The actual weight of fat in your body. Some Body fat is essential for maintaining body temperature, cushioning joints, and protecting internal organs.
- cardiac output: The amount of blood the heart pumps through the circulatory system in a minute.
- thyroid hormone: Thyroid hormones stimulate diverse metabolic activities leading to an increase in basal metabolic rate. One consequence of this activity is to increase body heat production, which seems to result, at least in part, from increased oxygen consumption and rates.
How do you calculate BMR?
Luckily many of us have devices that have calculated this number for us such as an apple watch, whoop, or fit bit. If you don’t you can use the calculations below to figure yours out. Here is a link to an online calculator if math scares you as much as it does me. My BMR comes out to just a little over 1200 calories a day. Yikes! I know I eat a lot more than that!
Here are the formulas using Harris-Benedict Formula
Men: BMR =(88.4 + 13.4 x weight in kilograms) + (4.8 x height in centimeters) – (5.68 x age)
Women: BMR = (447.6 + 9.25 x weight in kilograms) + (3.10 x height in centimeters) – (4.33 x age)
As I said, my BRM is slightly over 1200 calories per day, yet I consume anywhere from 1700-2000 plus calories on a typical day, so what else goes into metabolism? One thing is what is referred to as “NEAT”. What is it? Non-exercise activity thermogenesis (NEAT) is the energy expended for everything we do that is not sleeping, regular body functions, eating, or sports-like exercise. It ranges from the energy expended walking, typing, performing yard work, undertaking agricultural tasks, and fidgeting.
NEAT is often underestimated in weight loss. If you have a sedentary job it is easy to have a low NEAT. What are ways to increase your NEAT? Walk when you can, use a standing desk, take the stairs, do your own chores, cook your own food and stretch while watching TV.
Obviously many factors go into how many calories you burn during exercise including your fitness level/body composition, oxygen intake, weight, age, diet, sleep, temperature, and sex.
This formula can give you an approximation of how many calories you will burn:
Total calories burned = Duration (in minutes)*(MET*3.5*weight in kg)/2002
MET stands for Metabolic Equivalent for a Task
Luckily most of us have wearables that help us with this number. It’s typically defined as “active” calories.
Here is another way to get to a rough “guesstimate”
- Sedentary. If you get minimal or no exercise, multiply your BMR by 1.2.
- Lightly active. If you exercise lightly one to three days a week, multiply your BMR by 1.375.
- Moderately active. If you exercise moderately three to five days a week, multiply your BMR by 1.55.
- Very active. If you engage in hard exercise six to seven days a week, multiply your BMR by 1.725.
- Extra active. If you engage in very hard exercise six to seven days a week or have a physical job, multiply your BMR by 1.9.
OTHER FACTORS IMPACTING METABOLISM:
Everyone is a biochemically unique individual and while the above may be a good baseline and you can use it as a guide, along with any other tracking gadget you may have, it does not give you the entire story! There are many other factors that impact our daily requirements.
- Thermic effect of food: Foods such as protein and fiber require more energy to be broken down. They require more energy to digest suggesting adding in healthy protein and fiber can help you reach your goal.
- Body composition
- Weight history
- Microbiome (yes, your gut bugs can determine how easily you gain/lose weight)
- Lean mass
- Food timing
Putting it all Together:
There you have it, the items that make up your daily caloric needs:
Total Energy Expenditure (TEE)=BMR+NEAT+EXERCISE+OTHER FACTORS
Again, many of us have devices that track this at a basic level for us, but it is nice to understand the components and how we can control them. An apple watch can’t account for things such as hormone levels, your gut health, thyroid function, and more.
The old way of thinking that we just need to eat less and do more to lose weight is outdated and dangerous in my mind. I’ve actually seen many clients, who in an effort to lose weight, cut calories, and exercise obsessively while living on processed food/shakes and protein bars. Yes, this can work short-term, but to what long-term impact?
Cheers to your health! XDeeDee