Your metabolism is the chemical engine that keeps you alive.
The speed at which it runs varies by individual. Those with a slow metabolism tend to have more leftover calories, which get stored as fat.
On the other hand, those with a fast metabolism burn more calories and are less likely to accumulate a lot of fat.
This article reviews why some people have a fast metabolism and how you can speed up your metabolism to burn more calories.
What is metabolism?
Metabolism refers to all the chemical processes in your body. The faster your metabolism, the more calories your body needs.
Metabolism is the reason some people can eat a lot without gaining weight, while others seem to need less to accumulate fat.
The speed of your metabolism is commonly known as metabolic rate. It’s the number of calories you burn in a given amount of time, also known as calorie expenditure.
Metabolic rate can be divided into several categories:
- Basal metabolic rate (BMR): Your metabolic rate during sleep or deep rest. It is the minimum metabolic rate needed to keep your lungs breathing, heart pumping, brain ticking, and body warm.
- Resting metabolic rate (RMR): The minimum metabolic rate required to keep you alive and functioning while at rest. On average, it accounts for up to 50–75% of total calorie expenditure.
- Thermic effect of food (TEF): The number of calories burned while your body is digesting and processing food. TEF usually represents about 10% of your total energy expenditure.
- Thermic effect of exercise (TEE): The increase in calories burned during exercise.
- Non-exercise activity thermogenesis (NEAT): The number of calories required for activities other than exercise. This includes fidgeting, changing posture, standing, and walking around.
Summary: Metabolic rate is also known as calorie expenditure. It is the number of calories your body uses in a given amount of time.
Numerous factors affect your metabolic rate, including:
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- Age: The older you get, the slower your metabolic rate. This is one of the reasons that people tend to gain weight as they age.
- Muscle mass: The greater your muscle mass, the more calories you burn.
- Body size: The bigger you are, the more calories you burn.
- Environmental temperature: When your body is exposed to cold, it needs to burn more calories to prevent your body temperature from falling.
- Physical activity: All body movements require calories. The more active you are, the more calories you’ll burn. Your metabolism will speed up accordingly.
- Hormone disorders: Cushing’s syndrome and hypothyroidism slow down metabolic rate and increase your risk of weight gain.
Summary: Multiple factors affect metabolic rate, or the number of calories burned. These include age, muscle mass, body size, and physical activity.
Why do discrepancies exist?
Metabolic rates vary between people from birth.
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In other words, some people are born with a faster metabolism than others.
Although genetics may contribute to these differences, scientists don’t agree on the extent to which they affect metabolic rate, weight gain, and obesity.
Interestingly, most studies show that obese people have a higher total and resting metabolic rate, compared to normal-weight individuals.
Researchers note that this is partly because obese people have greater amounts of muscle to help support their extra weight.
Yet, studies indicate that obese people have higher metabolic rates irrespective of their muscle mass.
In contrast, other studies show that formerly obese people have a 3–8% lower metabolic rate, on average than those who have never been obese.
One thing is clear — not everyone is created equal when it comes to metabolic rate.
Most of this variation is due to people’s age, as well as their environment and behavior. However, the role of genetics in these individual differences needs to be studied further.
Summary: Metabolic rates vary by individual, even among infants. However, it is unclear how much of this variation is due to genetics.
What is the starvation mode?
Metabolic adaptation, also known as adaptive thermogenesis or starvation mode, may also play an important role in the development of obesity.
Starvation mode is your body’s response to a calorie deficit. When your body doesn’t get enough food, it tries to compensate by reducing its metabolic rate and the number of calories it burns.
The extent to which metabolic rate decreases during calorie restriction and weight loss is highly variable between individuals.
This metabolic slowdown is more pronounced in some people, especially those who are obese. The greater the slowdown, the more difficult it is to lose weight by dieting or fasting.
Starvation mode is probably partly affected by genetics, but previous weight loss attempts or physical fitness could also play a role.
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Summary: Metabolic adaptation or starvation mode is when metabolic rate slows down during a calorie-reduced diet or a fast. It varies between people and tends to be more pronounced among obese individuals.
Can you speed up your metabolism to lose weight?
Weight loss isn’t only about eating fewer calories. Effective weight loss programs also include strategies to speed up metabolism.
Here are eight simple methods.
1. Move your body
All body movement requires calories. The more active you are, the higher your metabolic rate.
Even very basic activity, such as standing up regularly, walking around, or doing household tasks, makes a major difference in the long run.
This boost in metabolic rate is technically known as non-exercise activity thermogenesis (NEAT).
In severely obese individuals, NEAT may account for a significant portion of daily calorie expenditure due to the extra weight they have to carry around.
There are several ways in which you can boost NEAT. If you spend a lot of time sitting, here are a few strategies:
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- Stand up regularly and walk around
- Take the stairs whenever possible
- Do household tasks
- Fidget by bouncing your legs or tapping your fingers
- Chew calorie-free gum
- Use a standing desk
If you have a desk job, using a standing desk may increase the number of calories you burn by 16%.
Another 10-person study showed that spending one afternoon standing burned an extra 174 calories compared to sitting.
Even seemingly insignificant activities like typing may increase your metabolic rate by 8% compared to doing nothing.
In the same way, fidgeting can make a significant difference.
One study found that people who sat motionless for 20 minutes temporarily increased their calorie expenditure by 4%, compared to when they lay motionless.
In contrast, fidgeting while seated increased calorie expenditure by a whopping 54%.
Regular exercise is highly recommended for anyone who wants to lose weight or improve their health. But even light activities like walking around, doing household tasks, or fidgeting can give you an advantage in the long run.
2. Do high-intensity workouts
One of the most effective forms of exercise is high-intensity workouts, also known as high-intensity interval training (HIIT).
HIIT is when exercise involves quick and very intense bouts of activity, such as sprints or fast push-ups.
It significantly speeds up your metabolism, even after the workout has finished — an effect dubbed “the afterburn”.
3. Strength train
Another excellent way to speed up your metabolic rate is to strength train.
In addition to the direct effect of the exercise itself, strength exercises promote the growth of muscle mass.
The amount of muscle you have is directly associated with your metabolic rate. Unlike fat mass, muscle mass significantly increases the number of calories you burn at rest.
One study showed that doing strength exercises for 11 minutes a day, three times per week, resulted in an average increase of 7.4% in resting metabolic rate after half a year — and an additional 125 calories burned per day.
Old age is generally associated with muscle loss and drops in metabolic rate, but regular strength exercise can partially counteract this adverse effect.
Similarly, a calorie-reduced weight loss diet often results in the loss of muscle mass and metabolic rate. Again, strength training may help prevent this decline.
A study in overweight women showed that doing daily strength exercises on an 800-calorie diet prevented decreases in muscle mass and metabolic rate, versus those who didn’t exercise or only did aerobics.
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4. Eat protein
Eating adequate amounts of protein is essential if you want to build or maintain your muscle mass. But dietary protein also has other important qualities.
All food leads to a temporary increase in metabolic rate, known as the thermic effect of food (TEF). However, this effect is much stronger after eating protein compared to carbs or fat.
Protein may increase metabolic rate by 20–30%, whereas carbs and fat cause a 3–10% increase or less.
This boost in calorie expenditure may help promote weight loss or prevent weight regain after a weight loss diet.
TEF is highest in the morning or during the first few hours after you wake up. For this reason, eating a large proportion of your daily calories early in the day can maximize the effect.
Eating high amounts of protein can also help counteract the loss of muscle mass and metabolic rate associated with weight loss.
5. Don’t starve yourself
While eating less is a key weight-loss method, eating too little is usually counterproductive in the long term.
That’s because calorie restriction causes a decrease in your metabolic rate.
This effect is known as the starvation mode or metabolic adaptation. It is your body’s way of warding off potential starvation and death.
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Research shows that consistently eating fewer than 1,000 calories daily leads to a significant drop in metabolic rate that sticks around even after you stop dieting.
Studies in obese people suggest that the starvation response may significantly reduce the number of calories burned. For instance, one study indicates that this slowdown in metabolic rate spares up to 504 calories per day.
Interestingly, intermittent fasting seems to minimize this effect.
6. Drink water
Temporarily boosting your metabolic rate doesn’t have to be complicated. It’s as simple as going for a walk or drinking a glass of cold water.
Many studies show that drinking water leads to an increase in the number of calories burned, an effect known as water-induced thermogenesis.
Drinking cold water has an even greater effect than warm water, as this requires your body to warm it up to body temperature.
Studies on this phenomenon provide varying results. About 16 ounces (500 ml) of cold water may cause a 5–30% increase in the number of calories burned for 60–90 minutes afterward.
It seems that increasing your water consumption is also beneficial for your waistline. Several studies show that drinking 34–50 ounces (1–1.5 liters) of water daily may lead to significant weight loss over time.
You can maximize these benefits by drinking water before meals, as it also fills you up and reduces calorie intake.
7. Drink caffeinated beverages
Although plain water is good on its own, caffeinated, low-calorie beverages, such as coffee or green tea, are useful as well.
Controlled studies show that drinking caffeinated beverages can temporarily speed up your metabolic rate by 3–11%.
However, this effect is smaller in obese people, as well as older adults. Additionally, seasoned coffee drinkers might have built up a resistance to its effects.
For weight loss purposes, sugar-free beverages like plain, black coffee are best. Like water, cold coffee may be even more advantageous.
8. Get good sleep
Getting inadequate sleep is not only bad for your general health, but it may also slow down your metabolic rate and increase your risk of weight gain.
One study showed that metabolic rate decreased by 2.6% when healthy adults slept for only four hours per night for five days in a row.
Another five-week study determined that sustained sleep disruption, along with irregular sleeping times, reduced resting metabolic rate by 8%, on average.
Accordingly, lack of sleep is associated with an increased risk of weight gain and obesity.
Summary: There are numerous things you can do to boost your metabolism. These include drinking cold water, sipping on coffee, getting more sleep, exercising, and eating protein.
Although your basal metabolic rate is largely beyond your control, there are various ways to increase the number of calories you burn.
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The strategies mentioned in this article can help you boost your metabolism.
However, metabolism isn’t everything when it comes to weight loss. It’s also vital to eat a healthy, well-balanced diet.