Whenever we hear about metabolism, the term calories often come to mind. Generally, weight loss and gain are dependent on how many calories we consume and how many are burned by the body. Resting calories play a significant role when it comes to this.
Unlike common belief, metabolism involves a series of activities taking place at the same time and is not a single mechanism. This also includes resting metabolic rate. We explore everything there is to know about resting calories and their significance to weight loss and gain.
What Are Resting Calories? (Also known as Resting Metabolic Rate RMR)
The human body needs the energy to perform functions like blood circulation or breathing. Your body converts the food you eat into units of energy (Calories) through a process referred to as body metabolism. The energy is used by the body immediately or stored for later use. The rate at which this process takes place is referred to as metabolic rate.
Generally, there are 3 numbers of calories in reference to metabolism – active, resting, and total calories. Resting calories, also known as Resting Metabolic Rate, refers to the number of calories the body needs to function while it is at rest. It is the energy burned while you are sleeping, sitting, or lying down. Primary functions include breathing, blood circulation, food digestion, heartbeat, and neurological functions.
On the other hand, active calories are those the body burns during physical exercises such as walking, playing football, hiking and cycling. Active calories are essential when it comes to losing weight. Total calories are the sum of resting and active calories. The total number of calories you burn each day is Total Daily Energy Expenditure (TDEE).
The Resting Metabolic Rate accounts for over 60% of the total energy expenditure. Often, the term Resting Metabolic Rate is used interchangeably with Basal Metabolic Rate. The two terms, however, mean two different things. Basal Metabolic Rate refers to the minimum number of calories you need to exist while the digestive system is inactive. RMR is an accurate estimate of BMR.
What Determines RMR?
For a majority of people, RMR can be calculated using known variables. These include age, weight, sex, and height. These variables are keyed into an RMR calculator and used to calculate how many calories your body needs daily to function.
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What Affects RMR?
Every person’s resting metabolism is different depending on several factors. The most significant factors that affect RMR include:
- Age. The RMR decreases as age increases. A younger person needs more energy to function compared to an older person.
- Gender. Men tend to have higher Resting Metabolic Rates than women as they are generally larger.
- Muscle. A more muscular individual requires more energy to maintain their body at rest compared to a less muscular individual. Therefore, more muscle increases RMR.
- Genetics. Your resting metabolism may be partly affected by genes.
- Body size: Larger adults have more body mass and have more metabolizing tissue, therefore having a high RMR.
- Pregnancy. Pregnancy increases the resting metabolic rate. RMR increases throughout pregnancy from the 1st trimester to the 3rd (2). This is due to increased body mass and physiological changes such as increased cardiac output.
- Climate. Living in an area with cold weather can increase your RMR. This is because the body must work harder to supply the body with adequate heat to maintain the average body temperature.
- Dieting. Regularly restricting food intake decreases your Resting Metabolic Rate (3).
How To Calculate Resting Calories?
Many online RMR calculators can be used to calculate your resting metabolism. They account for your physical activity and then tell approximately how many calories your body needs. You can also calculate resting calories in a lab, a gym, or by doing the math yourself. Remember, these calculators and tests estimate the resting calories burned daily and do not provide an exact figure.
After calculating your Resting Metabolic Rate, one might be curious to know if it falls within the normal range. The normal RMR is estimated to be about 1400 kcal per day for females and 1600 kcal per day for males. If your RMR falls somewhere above or below these values, then it is considered to be normal.
This is the simplest, most convenient way to calculate your resting calories. Search online for a Resting Metabolic Rate Calculator. Then input your age, gender, height, and weight. You need to know these before using an online resting calories burned calculator. Some also ask how active you are physically to give a more accurate estimate of total energy needs.
Calculate RMR In A Laboratory
Some clinics and health clubs may do tests to provide you with your RMR. The test takes about an hour. It may involve exercise testing. Most protocols require that you wear a mask for a certain period (about 15 minutes) while resting. This mask is used to measure the exchange of gases to determine the number of resting calories burned.
In the case you do exercise testing, you will be required to wear a mask while on a treadmill. This is done to measure the number of calories your body burns while working.
Calculate RMR Yourself
If you are a math lover, then you might as well calculate RMR yourself. A formula called the Harris-Benedict Equation is usually used to estimate Resting Metabolic Rate.
Men: RMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) – (5.677 x age in years)
Women: RMR = 444.7.593 + (9.247 x weight in kg) + (3.098 x height in cm) – (4.330 x age in years)
For example, the RMR of a 25-year-old male who weighs 70 kg and is 170 cm tall needs about 1700 Kcal per day at rest (using the Harris-Benedict Equation).
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How Do Resting Calories Affect Your Workout?
Exercising regularly increases the number of calories burned. It also increases your resting energy expenditure – the rate at which your body burns energy once the workout is complete and you are resting. Your Resting Metabolic Rate stays elevated if you exercise at least 3 to 4 times weekly. In the long run, RMR is increased due to an increase in lean body muscle (1).
During physical exercises like jogging, running, cycling or hiking, the body uses up glucose stored in muscles. It takes energy to replenish the glucose lost during exercise. So afterward, there is a need to refuel.
It is important to note that the kind of exercise also plays a key role when it comes to RMR. Certain types of exercise like lower intensity cardio and endurance focus more on burning fat and do not use up a lot of glucose. So, there is very little need to refuel because your glycogen stores haven’t been depleted. The nature of such low-intensity workouts is such that they do not affect the Resting Metabolic rate.
With high-intensity exercise, the case is different. With weight lifting and other high-intensity workouts, you use all the glucose in your muscles. As a result, the body has to send more fuel to the muscles which take longer. When the body is refueling, the amount of calories burned per day resting is increased as more food is turned into energy.
If you want to increase your metabolic rate, do high-intensity workouts that use up glucose in muscles compared to draining fatty acids. These include rope jumping, weight lifting, plyometric exercises, and hill walking.
Do Resting Calories Count Towards Weight Loss?
Weight gain results from the consumption of extra calories (More calories than the body requires). The average female requires 2,200 kcal while the average male requires 2,700 kcal daily to function properly. The extra calories are stored as fat and eventually cause weight gain.
If one individual reduces calorie intake and another increases physical exercise and doesn’t cut back on calories, the first individual will find it easier to lose weight. This is because it is harder to burn an extra 700 calories than to cut 700 calories from your meals in a day.
However, if you only cut back on calories, it is more likely that you will regain the weight lost. Why is this the case? The human body reacts to weight loss as if it is starvation, and consequently, body metabolism decreases. And even when you are resting, your body burns fewer calories.
When the body burns fewer calories, you either lose weight at a slower rate or do not lose weight at all. In the case you increase your calorie consumption, you may gain weight more quickly than you had previously. The solution is to strike a balance and increase your physical activity to counteract the slowed metabolism.
Resting Calories And Regular Exercises
Regular exercises increase the number of calories burned and the energy expenditure during rest. Regular exercises also temporarily increase your appetite. Often people joke about wanting a snack after exercise, but then they go ahead and indulge.
Since exercising regularly raises your calories resting metabolic rate, people continue to burn energy at very high rates. Thus a snack after a workout does not erase the effort of exercising regularly in helping people keep their weights in check.
To lose more weight, try to eat slightly less than your total calorie needs. You can also increase your level of physical activity to create an energy deficit. Some experts call it a calorie deficit. When you deny your body calories, it burns up stored fat as fuel. The result is that you cut weight.
The Bottom Line
Learning about your Resting Metabolic Rate and Total Daily Energy Expenditure can help you better plan your weight loss regime. The best way to lose weight is to combine dieting and exercise. But remember to consult your healthcare provider or a fitness specialist. Remember that you do not need to spend a lot of money on weight loss. All you need to do is set small achievable goals. In the long run, you will be able to lose weight and achieve your weight goals.
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This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility.
- Effect of Calorie Restriction on Resting Metabolic Rate and Spontaneous Physical Activity** (2007, researchgate.net)
- Energy Intake Requirements in Pregnancy (2019, ncbi.nlm.nih)
- Examining Variations of Resting Metabolic Rate of Adults: A Public Health Perspective (2015, ncbi.nlm.nih.gov)