Used often as an excuse for eating anything we want in our younger years, and more regularly as an excuse explaining why we have trouble reaching our weight loss goals, metabolism does play a big part in our body weight as well as energy balance. A greater understanding of what metabolism is exactly and the way you can use it to work for you, rather than against yourself, will help you gain and keep a healthy and fit body.
It is well known that if you wish to lose weight, you must make a negative energy balance. You must use up more energy than you are taking in.
Energy expenditure doesn’t only happen through physical exercise and activities. Our daily energy expenditure can in fact be divided directly into three categories:
Resting Metabolic Rate (RMR)
Thermic Effect of Food (TEF)
Expended energy used during physical activity (such as training)
We will only focus on RMR for now.
Resting Metabolic Rate is what we consider our metabolism. It is the total amount of energy (or calories) needed every day to keep one’s body working while it’s resting.
Specifically, it’s the energy that our brains working, our hearts pumping, and our lungs inhaling and exhaling, along with other cellular processes. It causes 60 – 75% of daily energy expenditure, maybe less in very physically active people.
Determining the RMR
RMR can range greatly person to person and there are a couple characteristics in each person which determine a person’s metabolism. For starters, the size of one’s body. A larger person generally has a higher metabolic rate than a smaller person. According to the surface area, a larger surface has a bigger metabolic rate. This means if two people weighed the same amount, the taller person will have a bigger metabolic rate because of their larger surface area.
However, the largest determinant of one’s metabolic rate is the body weight. The more you have of fat-free mass (bones, muscle, and organs), the higher your metabolism will be. This is because your fat-free mass is calorie-burning, or metabolically active, tissue. If two people were identical in height as well as weight, the person with more fat-free mass would possess the higher RMR.
Generally, athletes will have RMRs which are ~5% higher compared to a non-athletic person because they have more muscle mass rather than fat.
Knowing your fat-free mass is the greatest way of identifying your RMR and for that reason, your daily caloric requirements. The preferred technique of gaining fat-free mass is through underwater weighing. Air displacement as well as bone density scans are other popular techniques.
Once your fat-free mass is determined it may be used as part of a prediction equation, just like the Cunningham equation, to figure out your RMR:
RMR = 370 + (21. 6 x FFM[kg])
Age and gender also impact your metabolic rate. One’s metabolism peaks during growth spurts, like infancy or puberty. This is why your teenager may be seen hovering around the fridge!
As we continue to age, we begin to lose muscle mass and the metabolism will start to slow down. We lose approximately 2-3% of our earlier RMR every decade beyond being 30 years of age.
Because women usually have more body fat as well as less muscle compared to men, men generally have bigger metabolic rates. But men are still victims to a decline in their RMR as they age.
Other variables to consider while thinking of your metabolism include:
Hormonal disorders including hyperthyroidism, which increases your RMR, as well as hypothyroidism, which lowers your RMR.
An acute injury or an illness could temporarily boost your energy expenditure.
Having a fever also boosts the metabolic rate by about ~7% for each degree increase over 98.6° F.
And lastly, living and performing exercises in a nice tropical climate may increase your RMR between 5% and up to 20%.
The major question is how do you balance your weight loss and metabolism and figure out a healthy weight that allows you to be in your best condition, in an easily maintainable way. One tip is to make certain you don’t reduce calories too much.
1. Not having enough calories may result in the body breaking down protein, and muscle mass, to use as energy. Since muscle mass is the largest determinant of metabolic rate, the less we have of it, the lower our metabolism would likely be.
With a lower metabolism, less calories are essential for your daily maintenance, making it more difficult to lose weight.
2. The more we reduce our calories, the the better the body works at using calories that it gets.
This would normally be good, however it’s not when trying to lose weight. When creating a negative energy balance, or trying to cut our weight down, having the body efficiently using calories makes it work harder, burning up more calories.
3. Finally, the most difficult challenge about weight loss and metabolism is that once we lose weight, we need less energy. This is because RMR is mostly determined by your body mass. This mean you must lower your intake often to make up for the lower metabolic rate.
Some Tips For Maintaining Your Weight Loss And Metabolism
Begin and continue a weight training system and practice it 2-3 days a week to keep lean muscle mass. This will off-set the steady decline of metabolism that aging causes.
To avoid large drops in your RMR, limit your calorie restrictions to about ~15% lower than what must be met for your training and maintenance needs. If you required 2300 calories per day to meet the RMR and training expenditures, you should just drop that down by ~345 calories each day (intake ~1955 calories each day instead).
Set realistic weight goals and when you reach each goal, stop sticking to your diet. Your RMR will resume normally when your calorie restriction has stopped and an average caloric intake is begins.
Resist fighting your metabolism. Instead, discover ways to build your nutrition to mesh with it. Some variables causing metabolism are outside of our control or really hard to change. Metabolism is a specially tuned and a very regulated kind of operation our bodies carry out and it works best when it’s in balance.
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