Your Metabolism Explained, Part II

In my previous post, Your Metabolism Explained, I wrote about the three main ways our body uses energy: during rest, during activity, and during digestion. Thus, you can think of your metabolism as the following equation:

Metabolism = Basal Metabolic Rate + Activity Factor + Thermic Effect of Food

As a refresher, your Basal Metabolic Rate is the energy your body uses during rest. Your Activity Factory is the energy your body uses during any activity above and beyond sleeping (not only exercise, but also activities of daily living). Lastly, Thermic Effect of Food is the energy your body uses during the process of digestion.

There are many factors that can influence your metabolic rate. These can include your menstrual cycle, your age, your genetics, your activity levels, your food choices, and your history with dieting, among others. Let me explain how these factors can play a role in your metabolic rate.

If you have experienced a menstrual cycle, have you had the sensation of increased hunger during your cycle? This is a very common experience! The luteal phase of the menstrual cycle can increase how much energy your body is using upwards of 10% for some individuals. For example, if your body uses 2,400 calories on an average day, it could be using around 240 calories more during your menstrual cycle.

Age can also play a factor with metabolism. Typically, into adulthood, our bodies naturally start to lose some muscle mass. During this time, it is not uncommon for individuals to gain adipose tissue. Because muscle mass requires more energy to maintain than adipose tissue, this change can cause our metabolic rate to slow slightly. Research estimates that basal metabolic rate declines about 2% for every decade after 30 years of age. This is a pretty minimal amount, however as we age many adults tend to stop being as active. This reduced activity combined with the natural decrease in metabolic rate can have a greater effect.

Speaking of activity, physical activity impacts metabolism. Recall from the previous post that activity factor accounts for around 10-30% of your total energy usage. This strongly depends on the individual. A competitive athlete who is in peak training season, will likely be utilizing significantly more energy due to their physical activity than someone who works a job that requires sitting for several hours in a day. The important takeaway with physical activity, is to find activities you enjoy that you can do on a consistent basis. Walking, stretching, and playing intramural sports are all great options!

There are many factors that affect your metabolic rate, I could never cover all of them in one post. But the last one I want to focus on is so common, I would be remiss to skip over it.

Dieting… Ugh, where do I even begin?! Diets are often started with good intent. Maybe you’re looking to improve your health, or you think losing some weight would be good for your self-esteem. If you take anything away from this post, please let it be this: dieting backfires more often than not and is highly capable of causing a lot of harm. You see, when we diet, we initially lower our Thermic Effect of Food. We’re consuming less food therefore our body uses less energy to digest. This causes your metabolism to slow down.

Have you ever experienced that ever-so-frustrating “weight loss plateau”? Yep, that’s a sign that your metabolism has slowed to match the amount of energy you’re providing it. I’ll go out on a limb and guess that most dieters don’t want to slow their metabolism. I know this because I can go into nearly any supermarket and find a magazine or book on how to “Boost Your Metabolism in Three Easy Steps!” I smell total B.S.

Going on one diet, may not cause long-term damage to your metabolic rate. However, most dieters don’t go on just one diet. Most dieters fall into a category researchers call “yo-yo dieters.” These are individuals that go on diet, after diet, after diet, searching for the one that will finally work. This long-term behavior can cause major damage to your basal metabolic rate and take years to heal.

Here are some key points:

  • There are a multitude of factors that affect how much energy your body uses

  • Some factors are completely out of our control, like genetics

  • Some factors are within our control, like physical activity and our eating habits

If you want to get started on promoting an efficient metabolism, here are some of my suggestions:

  1. Ditch the diet! Aim for consistent meals and snacks every day.

  2. Eat a wide variety of foods, by not depriving ourselves of our favorite treats we can prevent overeating them when we do decide to eat them.

  3. Find a type of physical activity you enjoy and that you can do consistently. Don’t try to force yourself to go running 3 times a week if you hate running. It’s going to be really hard to make yourself do something long-term that you despise.

  4. Rest! Overworking yourself, including with physical activity, can cause stress, excessive lean body tissue breakdown, and can lead to burnout, illness, or injury. None of these things are a recipe for a healthy metabolism. Take rest days and get plenty of sleep each night.

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