Can Your Metabolism Change Suddenly?

There are many misconceptions about metabolism. In this article I will cover everything there is to know about how does metabolism change and what can affect it.

Can your metabolism change suddenly?

In general, your metabolism cannot change suddenly. Metabolism is the ability to extract energy and nutrients from the food and convert it into the usable forms of energy that is utilized by the body. The most significant contributors to metabolism is lean body mass and fat mass.

If you wanna know what really moves the needle and can give you this saucy physique all year round look no further.

What Can Change Your Metabolism?

Generally, your metabolism can be changed mainly by variations in your total daily energy expenditure and calorie intake. Factors that affect your metabolic rate include changes in lean body mass or fat mass, age, physical activity, quantity, and quality of food.

Of course, your metabolism is dynamic and can change in certain situations. But it does have a minor impact on your body.

The biggest ROI you get from amount of muscle mass, physical activity and food you eat.

Metabolism and Muscle

The more muscle mass you have, the higher your metabolism. Lean body mass is metabolically expensive. More muscle mass means you need to consume more oxygen.

And more oxygen means you will burn more calories.

About 4.7 calories are burned when 1 Litre of oxygen is consumed.

Muscle mass requires a gigantic amount of oxygen, comparing to fat mass. That’s why people who put on muscle will burn much more calories just because of the more demand.

And people who lost muscle mass will burn fewer calories.

On the other side, the antagonist for lean mass will be the amount of fat in the body. Increased fat mass lowers the demand for oxygen consumption and therefore decreases the number of calories we burn.

Metabolism and Physical Activity

Second thing that turns up your metabolism like a thermostat is a physical acivity. Resistance training and cardio.

  • Resistance training helps you add more lean mass
  • Cardio helps you to use more oxygen (burns more calories) and develop a strong heart

Plus, there is another component of physical activity called NEAT (non-exercise activity thermogenesis).

Those are all the things you do during the day from walking up the stairs, carrying the grocery, gardening, playing with kids, walking with dogs, etc.

Here’s the kicker.

Depending on your lifestyle, people who are physically active can burn tons of calories never put their foot down in the gym. And they can look fantastic.

Metabolism and Food

The last thing that will have an impact on your metabolism is food. Digesting the food is a process that also burns calories.

Certain foods can dramatically increase the amount of calories you burn, where other will stay at the low end.

The most metabolically expensive to eat are proteins, then carbs and fats at the end. This means you will burn more calories just from choosing more protein on your plate.

Metabolism and Weight Loss

Also remember that after significant weight loss our metabolism can slow down, too. When you lose a lot of weight and you suddenly eat less than usual, your body will need fewer calories therefore it will burn less energy (source).

How Do You Know If Your Metabolism Is Changing?

In general, you know if your metabolism is changing when your skeletal muscle decreases and the percentage of fat tissue increases. The most impact on the changes in metabolism will have the total volume of skeletal muscle, energy intake, and age.

But on the other side, if you’re physically active, you lift weights and eat a lot of protein that stimulates muscle protein synthesis, then you’re on your way to this absolute diced look where abs never go away.

The thing is that you cannot really “measure” your metabolism effectively. More on that later.

Metabolism and Age

And we get older, metabolism slows down. Physical activity, the thermogenic effect of food, lean body mass, and so on. So with those changes, you may notice that:

  • It takes longer to recover from workouts
  • Everything seems to be heavier
  • Some foods aren’t easily tolerated and digested anymore
  • Certain body parts start to feel more pain than others
  • We tend to catch a cold more often
  • We tend to feel more tired than usual

All those changes lead to lower physical activity, different food choices, and metabolic adaptations. That’s why it is imperative to lift weights, keep the lean mass on and stay strong for as long as possible (source).

How Do I Speed Up My Metabolism?

The most effective ways to speed up your metabolism are regular physical activity in the form of resistance training with progressive overload, a diet high in lean protein, minimally processed foods, and parasympathetic activities like breathing and meditation to reduce stress.

Also things like emotional balance, social interactions, sleep, and hydration plays a role in how effectively our body is breaking down food, storing fat, and building muscle.

  • Emotional balance

People who tend to regulate their emotions with food often end up having weight problems. Eating as the best or the only option to get by through the day, week or life will create this loop of the constant battle of gaining and losing weight.

  • Diet high in lean proteins

As discussed before, a high-protein diet not only burns more calories but also triggers muscle protein synthesis that leads to adding more lean mass. Which turns up the metabolism like a Traeger grill.

  • Minimally processed foods

Junk food will slow down your metabolism like no tomorrow. The more processed food you eat, not only you will feel crappier, but your hormones will be all over the place. Diets high in processed foods promote insulin resistance and can lead to some metabolic problems like diabetes.

  • Parasympathetic activities

Too much stress can rob you of your age quite quickly.

According to Robert Morris Sapolsky, an American neuroendocrinology researcher said that “If you turn on the stress response chronically for purely psychological reasons, you increase your risk of adult onset diabetes and high blood pressure. If you’re chronically shutting down the digestive system, there’s a bunch of gastrointestinal disorders you’re more at risk for as well.” (source).

That’s why people who have a lot on their plate, stress reduction activities like breathing, meditation, or yoga should be more regular.

How Is Metabolism Tested?

In general, your metabolism can be tested in the laboratory setting using direct or indirect calorimetry. Direct calorimetry measures the rate of heat produced by the body in an air-tight chamber, and indirect calorimetry measures the rate of air exchanged by the attached mouthpiece.

By far those are the two most accurate ways to measure and test metabolism. However, they are quite expensive to perform and not available to the mass market. That’s why there is plenty of estimate equation publicly available online that can give you a guess based on your age, weight, height,t, and physical activity (source).

The problem is that those estimates can be off by 20-30%.


  • There are multiple factors that can affect your metabolism, but those processes take time and cannot be changed suddenly.
  • The most impact on your metabolism will have lean body mass because it is the most metabolically expansive.
  • For best results, doing regular strength training, eating plenty of protein, taking a time to relax, and reduce processed foods will lead to an increase in metabolism.

Michal Sieroslawski

Michal is an exercise physiologist (MSc) and a veteran endurance athlete. He loves to experiment and share his successes and failures to help busy men and women who want to lose weight.

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