by Erin D Marion - Published 6 months ago

Metabolism Guide: Essential Tips

Contrary to popular belief, the majority of your daily calorie burn isn’t driven by exercise, but by your metabolism.

Metabolism is the entire process of converting calories into energy for your body. It determines how many calories you need daily to maintain your weight.

THREE SCIENCE-BACKED WAYS TO BOOST YOUR METABOLISM

While there's much to learn about metabolism, most people are interested in how to increase it. If you're experiencing a weight-loss plateau, you might be overestimating your calorie burn.

1. INCORPORATE STRENGTH TRAINING INTO YOUR EXERCISE ROUTINE

Building muscle boosts your Basal Metabolic Rate (BMR), the primary factor influencing your overall metabolism. This enables you to burn more calories even when not exercising. Explore our article, So You Want to Start…Strength Training for further insights.

2. ENHANCE YOUR WORKOUT INTENSITY

While engaged in aerobic activities (running, swimming, cycling, HIIT), integrate intervals to harness the 'afterburn' effect, where you burn additional calories post-workout.

3. FULFILL YOUR DAILY PROTEIN TARGET

Your muscles need a full set of amino acids to rebuild and grow after a workout. High-quality protein sources deliver these. Find out how much protein you need in our Essential Guide to Protein.

TYPES OF METABOLISM

Calories enter our bodies in one way, but leave in many. These are the top three influences on your metabolism and how many calories you burn.

BASAL METABOLIC RATE (BMR): CALORIES TO SURVIVE

BMR is responsible for 60–70% of the calories you burn daily.

Basal metabolic rate (BMR) is the number of calories your body needs at rest to support essential functions like breathing, digesting, and filtering waste. Your BMR doesn't include calories burned during daily activities or exercise.

Here are the key factors affecting BMR:

Body Size: A larger individual requires more calories to maintain their body at rest and during any activity they do.

Body Composition: Muscle is more metabolically active than fat, meaning more calories are burned to maintain a pound of muscle compared to a pound of fat. Two healthy individuals of the same age, height, and weight can have significantly different BMR if they have different percentages of lean versus fat mass. Since most women have more fat mass compared to men, they have correspondingly lower BMR compared to men of the same height and weight.

Age: Your BMR is higher when you are younger, especially since calories are needed for your growing body. As you age, you tend to gain fat mass and lose muscle mass, which slows down your metabolism. Read 5 Ways to Cope with a Slowing Metabolism to learn more about how aging affects your metabolism.

Genetics: Some people are born with higher (or lower) BMR than others, which is normal. While you can't change your genes, if you suspect a genetic condition that slows your metabolism (like familial hypothyroidism), consult a medical professional.

Hormones: Hormones regulate your metabolism, turning it up or down depending on your body's needs. Thyroxine and triiodothyronine, from your thyroid gland, directly increase BMR. Other hormones indirectly influence the release of these hormones, impacting your BMR.

Health: Generally, your BMR is higher when you're fighting an infection or recovering from a major injury, as your body requires more calories for these tasks.

Because these factors make BMR calculation variable, accurately determining someone's exact BMR without specialized equipment is difficult. The Mifflin–St. Jeor equation is commonly used to estimate BMR, proving to be most accurate for healthy adults compared to other existing equations. This equation considers your gender, body size, and age when calculating your daily calorie goal. You can experiment with this equation using the MyFitnessPal BMR calculator.

FOOD THERMOGENESIS: CALORIES TO DIGEST

Consumes about 10% of the calories you burn daily.

This term, though difficult to pronounce, is relatively straightforward. Food thermogenesis refers to the energy (calories) required for your body to break down and absorb food. Among macronutrients, protein demands the most energy for digestion, followed by carbs and fats. Roughly 10% of your daily calorie intake is used for digesting and absorbing a meal with diverse macronutrients. Here's a more detailed breakdown:

Approximately 0–3% of the calories from consumed fat are used for its digestion.
About 5–10% of the calories from consumed carbs are used for its digestion.
Around 20–30% of the calories from consumed protein are used for its digestion.

A diet high in protein and low in carbohydrates aims to utilize this phenomenon for calorie burning, as protein digestion requires more energy than carbs or fat. However, since food thermogenesis accounts for only 10% of your daily calorie expenditure, increasing protein intake will have a minimal impact on your metabolic rate. Although protein aids in weight loss, you should consider the downsides of excessive protein consumption, including potential strain on your kidneys.

PHYSICAL ACTIVITY: CALORIES FOR MOVEMENT

Physical activity accounts for 20% of your daily calorie burn, but can be higher on intense workout days.

Beyond workouts, your job and leisure activities also contribute to calorie burn. Activities like typing, carrying loads, standing, fidgeting, shopping, playing, and singing all contribute.

MyFitnessPal factors in activity level (sedentary, lightly active, active, very active) to estimate your daily calorie burn.

UNDERSTANDING YOUR MACRONUTRIENT FUEL

Our bodies use carbohydrates, fat, and protein as energy sources. The type of activity determines which fuel is primarily utilized.

Here are some common conditions:

Exercise above 70% maximal heart rate: At this intensity, it's hard to talk because your body focuses on breathing to deliver oxygen to your exercising muscles. In this situation, your body relies on carbohydrates for fuel because carbs can be burned quickly and work in low-oxygen environments.
Exercise below 70% maximal heart rate: At this intensity, you can chat with a jogging partner while getting enough oxygen. In this case, your body prefers fat as fuel since it's a slow-burning source that's ideal when plenty is available.
Overnight fast: Your metabolism slows down while you sleep, but your body needs calories to repair cells and maintain basic functions like breathing. Because you won't be eating for 8-12 hours, your body will use fat to fuel most tissues and carbohydrates to fuel your brain. The carb that fuels your brain is glucose, usually stored as glycogen (stored carbs) in your cells. If there isn't enough, your blood sugar drops, and protein is used for fuel, as it can be converted into glucose to bring your blood sugar back to normal.
Starvation: Your metabolism slows down significantly, making you feel tired and irritable. Protein and fat become the primary sources of fuel. After 48 hours without food, your body runs out of glycogen to power the two organs that need it most: your blood cells and your brain. While blood cells can only run on glucose, the brain will start to use fat in the form of ketone bodies. Your body increases the breakdown of muscles and organs for protein fuel and fat pads for fat fuel.

Additionally, certain diseases and conditions can affect the fuel your body uses most. For example, if you're recovering from a third-degree burn, you'll need more protein fuel to heal and rebuild tissues.

You can also change the fuel type your body prefers during exercise by training. As you train, your body becomes more efficient at using oxygen during exercise. This allows you to burn more fat during higher-intensity exercises instead of mostly carbohydrates. As a result, you can perform at a higher intensity (for example, run, cycle, and swim farther and faster) without feeling tired.

FIVE METABOLISM MYTHS, DEBUNKED

1. THE “FAT-BURN ZONE” ON YOUR EXERCISE MACHINE IS THE BEST SETTING FOR WEIGHT LOSS

The “fat-burn” zone on your exercise machine may burn a larger percentage of calories from fat, but it burns fewer overall calories because it operates at a slower pace. More intense exercise can burn more calories, making it more effective for weight loss.

2. EATING SIX SMALL MEALS DAILY BOOSTS YOUR METABOLISM

Eating six small meals won't increase your metabolism if you consume the same amount of calories. It may help control hunger, but it also increases the chance of overeating.

3. THINNER INDIVIDUALS HAVE A HIGHER METABOLISM

It's not true! People who are thinner generally have slower metabolisms than heavier people because heavier people need more calories to support their larger organs.

4. LATE-NIGHT EATING WILL MESS WITH YOUR METABOLISM AND CAUSE WEIGHT GAIN

Your metabolism does slow down at night, but your body will still process the food you eat the same way. As always, focusing on the quality and quantity of calories is most important.

5. DRINKING GREEN TEA WILL MAKE YOU BURN MORE CALORIES

Green tea contains catechins, which are thought to aid in fat burning. A few small studies suggest that drinking green tea might help with weight loss, but the effect is minimal and the study results were not consistent. If you enjoy green tea, feel free to drink it, but don't rely on it for any significant metabolic boost.