- What Exactly is Metabolism?
- Different Types of Metabolism
- What Contributes to Fast Metabolism?
- How Starvation Mode Affects Your Metabolism
- Can You Change Your Metabolism?
- 4 Ways to Improve a Slow Metabolism
- How to Gain Weight if You Already Have a High Metabolism
- How Going Keto Can Help Your Metabolism
When it comes to permanent weight loss, basic low-calorie diets don’t work well. While it’s true that you have to be in a calorie deficit to lose weight, simple calorie-counting is not a useful strategy for sustainable weight loss[*].
A lot of weight loss comes down to your metabolism. Your metabolism is, in a nutshell, how much energy you use throughout the day, and how well your body uses that energy.
You have a lot of control over how your metabolism functions. Improving your metabolism makes it easier to lose weight, and a balanced metabolism is a good predictor of a long, healthy life.
Read on to learn what type of metabolism you have, the factors that influence your metabolism, and how to safely speed it up, plus what to do if you have a high metabolism and want to gain weight.
Your metabolism is the collection of daily processes your body uses to create energy. Your metabolism fuels everything you do, so it’s worthwhile to become friendly with it. That means figuring out how you can support your metabolism and make it as strong as possible.
The three main roles of your metabolism are:
- Converting food to energy for your cells
- Turning foods into building blocks for proteins and fats to maintain your body’s tissues
- Eliminating waste from your body
Your body is constantly adapting to your needs. It’s making energy, breaking down and rebuilding cells and tissue, and eliminating waste, which means it’s impossible to get an exact measurement of your actual daily metabolism.
However, calories — a measure of the heat produced during combustion — are one way to measure the energy content of food and estimate how much food your body needs each day.
How Your Body Uses Calories
Here’s how your body uses calories in the food you eat:
- Your basal metabolic rate (BMR) is the baseline number of calories your body uses to keep you alive each day. You can think of BMR as the number of calories you would burn if you lay in bed doing nothing all day. BMR includes the energy that keeps your heart pumping and lungs breathing and runs all the background processes that help you survive.
- The thermic effect of food (TEF) refers to the number of calories your body uses to digest meals, which is usually about 10% of your overall calorie intake. You can adjust the thermic effect of food to burn more or fewer calories each day, depending on the type of food you eat. More on that later.
- The thermic effect of exercise (TEE) is the number of calories your body burns during physical activity or exercise.
- Non-exercise activity thermogenesis (NEAT) refers to calories you burn during non-exercise activities like sitting, standing, driving your car, or adjusting your posture.
Calorie needs change from day to day, and while your daily calorie needs are related to your metabolism, the two concepts are not interchangeable. Metabolism involves more than just the calories you burn.
Your metabolism may be naturally faster or slower, depending on genetic and environmental factors. A lot of people use this as an excuse for not losing weight, but the truth is that even if your metabolism is naturally slower, there’s a lot you can do to speed it up.
In addition to speed, your body can rely on two different kinds of fuel: either ketones (fat) or glucose (sugar).
The food you give your body determines which type of fuel it uses. If you eat carbs, it will burn glucose. If you limit carbs, like on a ketogenic diet, or you deplete your glucose stores through intense exercise, your body will switch to burning fat.
How Your Body Burns Energy
Your metabolism also has two energy-burning modes, depending on the presence or absence of oxygen.
- Anaerobic metabolism, which occurs during intensive exercise or when your body is deprived of oxygen, relies on glucose (a simple sugar), lactate (a byproduct of burning sugar), and amino acids (protein) for fuel. You can’t burn fat anaerobically.
- Aerobic metabolism requires oxygen to burn fuel. Aerobic metabolism turns on once your anaerobic metabolism the only way your body can burn fat, although it can also use glucose or amino acids to create energy.
To summarize, your metabolism can be fast or slow, sugar-based or fat-based, and anaerobic or aerobic. Most healthy people rely on a combination of sugar- and fat-based metabolism and their bodies use both anaerobic and aerobic pathways.
However, in people with obesity, insulin resistance, and other health problems, the sugar-based anaerobic pathways may be more active[*][*]. This imbalance results in increased inflammation, oxidative damage to tissues, reduced brain function, and a higher risk of cancer[*][*][*][*][*].
A wide range of factors influence your metabolism.
#1: More Lean Muscle Mass
The more lean muscle mass you have, the higher your metabolism will be[*]. Muscle uses more energy than fat does, which means putting on muscle will increase your basal metabolic rate, and the more muscular you are, the more calories you’ll burn in a day.
Exercise speeds up your metabolism, both during and after a workout.
#3: Hormone Levels
Your hormone levels also contribute to your unique metabolic profile. Energy regulation hormones like cortisol, thyroid hormones, and insulin can interact with one another to speed up or slow down your metabolism. Diet, sleep, stress, and other lifestyle factors play a huge role in your hormone function.
Diet affects your metabolic rate directly, through the thermic effect of food, and indirectly through your hormones and your gut flora population[*].
Finally, age influences your metabolism. As you get older, your metabolism slows down[*].
People with a healthy, high metabolism usually have a relatively large amount of lean muscle mass, are physically active, have balanced hormones, and have healthy, balanced gut bacteria that differ from the gut bacteria of overweight people[*][*][*].
Starvation mode is a name for your body’s natural response to a chronic, severe caloric deficit.
Because your brain and body are more concerned with long-term survival than with losing body fat, eating insufficient calories can act as a starvation signal. In response, your body may put the brakes on fat loss and slow your metabolism[*].
- Physical inactivity
- Excessive hunger
- Food cravings
Staying in starvation mode long-term can result in serious hormonal imbalances, extreme difficulty maintaining a stable body weight, and health problems[*][*]. These harmful effects are called “metabolic damage.”
What is Metabolic Damage?
Metabolic damage involves disruptions in hunger hormones, loss of lean muscle mass, and–in severe cases–damage to your organs. Researchers have documented the occurrence of hair loss, diabetes, and heart failure due to metabolic damage from long-term, very-low-calorie diets[*][*][*].
To be clear, starvation mode is not the same as a mild or short-term calorie deficit. Starvation mode happens when you consistently undereat and your body isn’t getting even close to the energy it needs.
To avoid starvation mode and prevent metabolic damage, it’s imperative that you plan well if you’re going to lose weight. You want to be in a sustainable, slight caloric deficit.
If you’ve been trying to lose weight and you find you’re exhausted and hungry all the time, you may not be eating enough, which will paradoxically slow down your weight loss. Try using this macro calculator to figure out how much you should eat to gradually, sustainably lose weight. Permanent weight loss is a marathon, not a sprint.
The good news is that you can change your metabolism.
If you suspect you may have a slow metabolism, remember that your metabolic rate is only one factor that impacts your weight loss results.
You can shift your metabolic type to favor increased energy expenditure, aerobic metabolism, and fat loss by increasing your lean muscle mass, balancing hormones like insulin and cortisol, and changing your diet.
#1: Go Keto
One of the easiest ways to increase your metabolism is to switch your source of fuel from carbs to fat.
People on a ketogenic diet burn an average of 300 extra calories per day, compared to people on a higher-carb diet[*]. Researchers suspect that the reason is thermogenesis — animal studies suggest that if you’re running on fat, your body produces more heat when you’re at rest[*][*].
It can take several weeks to adapt to the ketogenic diet fully, but once you do, you can look forward to a faster metabolism. Keto also suppresses appetite, which can make it easier to lose weight without feeling hungry[*].
#2: Eat More Protein
Adding more protein to your diet is an excellent way to speed up your metabolic rate. Protein is very thermally active; thanks to the thermic effect of food (TEF), a high-protein meal can double the amount of fat your body burns for up to six hours compared to a typical meal[*].
The type of protein you consume makes a difference, too. One study found that a 30-gram dose of whey protein increased the metabolism of overweight adults by 13%, while 50 grams of whey protein increased it by 18%[*]. Casein protein was less effective than whey[*].
#3: Exercise At Moderate Intensity
It’s no secret that physical activity is your friend if you want to shed fat, but the type of exercise you choose matters.
Here’s how you should exercise to boost your metabolism:
- Strength training once or twice per week can help you build muscle mass, or maintain muscle during fat loss[*][*]. The more muscle you have, the more calories you’ll burn throughout the day.
- Low- to moderate-intensity aerobic exercise is the best way to burn fat during exercise[*].
- Interval training increases the calories you burn after exercise more than other forms of activity[*][*][*][*].
- Walking daily and moving more increases your daily caloric expenditure and helps you recover from other types of activity[*].
If you’re new to exercise, start slowly. You can begin with daily walks and one or two other sessions of your choosing per week, then add more gradually.
Ideally, your weekly workout routine will include weightlifting (for muscle gain) with moderate-intensity cardio (for fat burning) and high-intensity interval training (for faster metabolism after you work out), plus plenty of walking.
#4: Try Intermittent Fasting
Intermittent fasting is an eating pattern involving planned periods without food intake. You can do it daily for brief or medium durations, or a few times a week for longer.
Contrary to what you may have heard, fasting won’t put you into starvation mode. Instead, it puts you in fat-burning mode and helps you burn through your body fat stores[*].
Fasting can also make it psychologically easier to stay in a mild calorie deficit, which simplifies weight loss. You can skip breakfast and then eat until you’re full for lunch and dinner, and you’ll go to bed satisfied while still under calories.
If you happen to have a fast metabolism, you may have difficulty gaining weight. While being underweight doesn’t carry the same health risks being overweight, it can be frustrating trying to put on weight if you have a fast metabolism.
In older people, a low body mass index (BMI) can lead to frailty, higher risk of injury from falls, and reduced quality of life[*][*][*]. Depression, health issues, and prescriptions medications are common reasons for unintentional weight loss in senior citizens[*].
Excessively high levels of thyroid hormones, called hyperthyroidism, is one cause of low BMI[*][*][*]. If you’re thin and have trouble gaining weight, you can ask your doctor to screen you for hyperthyroidism.
If you don’t have thyroid problems, here’s how to achieve a healthy weight with a high metabolism:
#1: Reduce Stress
It might seem easier said than done, but reducing chronic stress can help reset your metabolism. Stress increases your cortisol levels, which can make it hard to gain healthy weight.
#2: Strength Train
Lift weights or do another form of strength training twice a week to add lean muscle mass. Work out more to gain weight? Take a look at #4 to make sure you’re getting enough healthy protein.
#3: Sleep More
Sleep deprivation can adversely affect your metabolism and cause you to lose muscle tissue[*][*][*][*]. Bad sleep habits also contribute to the stress load on your body and can result in hormonal imbalance.
#4: Eay More Protein
Eat more protein — whey protein in particular is an excellent choice to gain healthy weight, especially post-workout[*].
#5: Eat Nutrient-Dense Foods
Consume nutrient-dense, calorie-dense foods like nuts, avocados, and fatty grass-fed beef. Check out this low-carb food list for a comprehensive grocery list of nutrient-dense keto foods.
Along with these recommendations, you can also use the Perfect Keto Macronutrient Calculator to calculate the proper calories and macros to allow you to gain weight. Try weighing in once every week or two; if you don’t gain any weight for two consecutive weigh-ins, you can increase your calories by another 5-10%.
Another way to improve your results is to try the cyclical ketogenic diet or targeted ketogenic diet. Because these keto approaches utilize carbohydrates to fuel activities like resistance training, they’re fantastic for gaining healthy weight and supporting your strength training regimen.
The ketogenic diet alters the expression of metabolic genes to put you in ketosis, a state where you burn almost exclusively fat for fuel[*][*][*][*]. That means that by turning specific genes on or off, eating keto speeds up your metabolism, increase your insulin sensitivity, and favors aerobic metabolism and fat-burning[*][*][*][*].
To be clear: just because you’re burning fat for fuel doesn’t mean you’re burning body fat. If you eat more calories than your body uses while on a ketogenic diet, you’ll still put on fat. However, being in ketosis suppresses appetite, and many people find they spontaneously eat less and lose weight without feeling hungry while on keto[*]. Being in ketosis increases the calories you burn while decreasing hunger, which is a perfect recipe for weight loss[*].
Keto has other metabolic benefits too. Eating a ketogenic diet improves fasting insulin levels more, causes more weight loss, and lowers triglyceride levels more than eating a low-fat diet does[*][*].
Before you worry about having a fast or slow metabolism, it’s important to realize that you have much more control over your metabolism than you might think.
Calories are important, but if you’re struggling to lose weight, pay attention to other components of your diet besides your caloric intake. You can achieve better results by customizing your diet and lifestyle to increase your metabolism and shed fat more easily.
A ketogenic diet is one of the best ways to speed up your metabolism and lose weight without getting hungry. Get started on a keto diet today with this complete beginner’s guide to keto.