Have you ever heard someone has a “high” or “low” metabolism? You may envision the person with a high metabolism requiring thousands more calories each day compared to the one with low metabolism. Did you know that 96% of people stay within 200-300 calories of the average metabolism? Then why is it some people restrict their calories and exercise like a fiend but struggle with consistent weight gain? Others eat whatever they want without exercising and have a difficult time maintaining weight. This doesn’t seem fair.
To understand your unique metabolism and how to stoke the fire to get it to burn hotter, we need a little Metabolism 101 class. Keep reading to briefly touch on the following topics:
What is Metabolism?
a. What is the most effective way to lose weight without decreasing metabolic rate?
2. What makes up my Total Daily Energy Expenditure or TDEE?
a. Resting Metabolic Rate (RMR)
b. Non-Exercise Activity Thermogenesis (NEAT)
i. Ideas for moving more during the day
c. Thermic Effect of Food (TEF)
i. Which foods burn the most calories to digest?
d. Exercise Activity Thermogenesis (EAT)
i. Which types of exercise are best for boosting the metabolism?
3. Conclusion
Increase the Calories You Burn at Rest. Let’s Get Started!
Metabolism is the process where your body uses the food and drink you consume each day to make into energy. The calories in what we consume are combined with oxygen to provide your body energy to function. Even when you are sleeping, your body requires energy to breathe, create and grow cells, circulate blood and all the other basic functions we need to live. The number of calories required for these basic functions is known as your basal metabolic rate (BMR).
Obesity is associated with a higher metabolic rate due to the heavier body requiring more energy to function. There is a risk of slowing metabolism when extreme caloric restriction is used, and a fast weight loss is experienced. Studies have shown that formerly obese individuals have a 3-5% lower metabolic rate compared to others. Due to this, recommendations for slower weight loss (1-2 pounds per week) with less extreme caloric restrictions combined with adequate protein intake and strength training are ideal to promote maintenance of a healthy metabolic rate.
Resting Metabolic Rate (RMR)
RMR is the number of calories you need in a resting state. It is slightly higher than your basal metabolic rate and is a term used more often for estimating a person’s daily calorie needs. Always remember, these are estimations and only as good as the formula or method used. The RMR makes up ~70% of your total daily energy expenditure (TDEE).
Your RMR can be affected by the amount of fat mass vs fat free mass in your body because various tissues burn calories at different rates.
Your brain and organs are very metabolically active making up ~12% of your RMR or ~200-440 kilocalories per kg weight of the organ per day.
Even though these organs don’t weigh much compared to muscle, ounce per ounce, they require more calories to function than other tissues.
Skeletal muscle uses ~13 kilocalories per kg weight of lean mass per day.
Increasing your muscle mass through strength training helps increase the calories you burn at rest.
Fat mass is much less metabolically active at ~4.5 kilocalories per kilogram of fat mass per day. Fat stores burn calories but at a much slower rate than muscle.
Since increasing the mass of your organs is not a possibility, the primary way to increase RMR is by increasing muscle. Building muscle requires doing activity which fatigues that muscle causing small tears in the tissue. With adequate protein intake and recovery, that muscle repairs itself and becomes stronger.
Unfortunately, RMR decreases with age due to decreased muscle mass as well as decreased energy-generating mitochondria living in the cells. RMR can be 20-25% lower in adults >70 years of age compared to younger adults. This makes it even more important to continue to be active with age and specifically incorporating strength training and weight bearing exercise into daily routines to maintain muscle mass and bone strength.
Interesting Fact!! Your body uses 2/3 of your RMR calories just maintaining your body temperature!
Non-Exercise Activity Thermogenesis (NEAT)
NEAT includes all the activities you do during the day EXCEPT exercise. It makes up 15% of your daily calorie expenditure meaning it is the second largest portion next to RMR and can range from 100-800 calories per day. This is an area where most of us could improve, especially those of us who work sedentary jobs which require sitting for large parts of the day.
How can you improve this? Find ways to move more during the day!! Here are some ideas:
1. Use a standing desk for work off and on during the day.
2. Sit on a stability ball while working on the computer.
3. Take a walk over your lunch break.
4. Get up and stretch for a few minutes every hour.
5. Take a 5-minute dance break.
6. Use the stairs instead of the elevator.
7. Park farther away in the parking lot.
8. Rather than sitting and watching TV at night, take the dog for a walk, go pull some weeds or do some household chores.
Another Interesting Fact: By standing ~1/2 of an 8 hour workday, you can burn an extra 200 calories compared to sitting.
Thermic Effect of Food (TEF)
Did you know you burn calories just by eating? Thermic effect of food is the increase in metabolic rate occurring after you eat and typically makes up ~10% of the total daily energy expenditure. The body uses energy or calories to digest, absorb and store the nutrients in food you have eaten. There is conflicting evidence on whether more frequent meals, versus skipping meals, increases or decreases the TEF. Timing of the meal and the type of food eaten can affect the TEF.
The TEF of the three macronutrients varies:
1. Fat: 0-3%
2. Carbohydrates: 5-10%
3. Protein: 20-30%
As you can see, high protein foods have a significantly higher TEF than the other 2 macros. In addition to this benefit, protein promotes satiety or that feeling of fullness. Increased protein intake can help with maintenance of muscle mass and fat loss when an individual is consuming at a calorie deficit with the goal of weight loss. Less processed foods that are higher in fiber require more energy to break down compared to highly processed foods. Even though high fiber foods take more calories to digest, there is no such thing as a negative calorie food. Even celery which is very low calorie, contains more calories than it costs the body to digest it.
Does this mean a person should avoid fat and carbohydrates in meals? Absolutely not! In each meal and snack, choose a high protein food as well foods high in fiber like vegetables/fruits, whole grains, beans/legumes and nuts/seeds to maximize the TEF. This is also beneficial for blood sugar management because protein and fiber lessen blood sugar spikes.
Studies have shown that physically active individuals generally burn more calories with food consumption in general. Yet another reason to be physically active!!
Exercise Activity Thermogenesis (EAT)
Finally, the last piece of the pie is Exercise! EAT makes up the last 5% of the TDEE but when coupled with NEAT, is the most variable aspect making up ~15% of TDEE in sedentary people and up to 50% of TDEE in highly active ones.
Depending on the duration and intensity of the exercise, you can have increased metabolism for up to a day after the end of the exercise. This is called EPOC which stands for excess post-exercise oxygen consumption. Aerobic exercise like running, walking, kickboxing, swimming and biking can burn more calories during the activity but does not have as much of an EPOC effect compared to Anaerobic exercise.
The exercise which most affects EPOC is the kind which builds muscle. Increased energy is required through the process of damaging those muscles and repairing them.
We have also learned above that muscle burns more calories at rest than fat so strength training will provide more long-term metabolic benefits than other forms of exercise.
Conclusion
Our metabolism is the furnace of our bodies. To make our furnaces burn more calories during the day:
increase muscle through strength training
find ways to be more active during the day
consume mixed meals which include high protein and high fiber foods
We can also benefit from regular exercise to increase our metabolism for up to 24 hours after a workout. It is especially important to incorporate strength training into exercise routines for older adults to maintain muscle mass and combat decreasing metabolic rates.
What do you do to keep up your metabolism? Please comment below with answers or any feedback you would like to provide. Thank you for reading to the end.
References:
Kimberly Duffy, RDN, LD, CPT
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