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By Dr. Atli Arnarson

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 fuel (calories), which gets 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 is a review of why some people have a fast metabolism and how you can speed up your metabolism to burn more calories.

What Is Metabolism?

Metabolism is a term that collectively refers to all the chemical processes in your body. The faster your metabolism, the more calories your body needs.

This is the reason some people can eat a lot without gaining weight, while others seem to need less to accumulate fat.

The "speed of 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 when you are asleep or at deep rest. It is the minimum metabolic rate needed to keep your body warm, lungs breathing, heart pumping and brain ticking.
  • 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 percent of total calorie expenditure (1).
  • Thermic effect of food (TEF): The number of calories burned when your body is digesting and processing food. The rise in metabolic rate after meals usually represents about 10 percent of total energy expenditure (2).
  • Thermic effect of exercise (TEE): The number of calories burned during exercise.
  • Non-exercise activity thermogenesis (NEAT): The number of calories burned during activities other than exercise. This includes fidgeting, changing posture, standing and walking around (3).

Summary: Metabolic rate is also known as calorie expenditure. It is the number of calories used by the body in a given amount of time.

What Factors Affect Metabolic Rate?

Numerous factors affect your metabolic rate. To name a few, these include:

  • Age: The older you get, the slower your metabolic rate becomes. This is one of the reasons people tend to gain weight as they age (4).
  • Muscle mass: The greater your muscle mass, the more calories you burn (5).
  • Body size: The bigger you are, the more calories you burn (6).
  • Environmental temperature: When your body is exposed to cold, it needs to burn more calories to prevent your body temperature from falling (7).
  • Physical activity: All body movements require calories. The more active you are, the more calories you'll burn. Your metabolism will speed up accordingly (8).

Summary: Multiple factors affect metabolic rate or the number of calories burned. These include age, muscle mass, body size and physical activity.

Are Some People Born With a Fast Metabolism?

Metabolic rates vary between people, even when they are newborns.

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 (10, 11).

Interestingly, most studies show that obese people have a higher total and resting metabolic rate, compared to normal-weight individuals (12, 13, 14, 15).

Researchers have pointed out that this is because obese people have greater amounts of muscle to help support the extra weight (15, 16, 17).

Yet, studies indicate that obese people have higher metabolic rates, irrespective of the amount of muscle mass they have (18, 19).

In contrast, other studies show that formerly obese people have a 3–8 percent lower metabolic rate, on average, than those who have never been obese (10, 20).

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.

Metabolic Adaptation

Metabolic adaptation, also known as adaptive thermogenesis or "starvation mode," may also play an important role in the development of obesity.

Starvation mode is the 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 (21, 22, 23, 24).

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 (21, 25, 26).

Starvation mode is probably partly affected by genetics, but previous weight loss attempts or physical fitness could also play a role (27, 28).

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.

By Helen West

Intermittent fasting is an eating pattern that involves periods of food restriction (fasting) followed by normal eating. This pattern of eating could help you lose weight, reduce your risk of disease and increase your lifespan (1, 2).

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EcoWatch Daily Newsletter

By Alina Petre

Certain foods can increase your metabolism.

The higher your metabolism, the more calories you burn and the easier it is to maintain your weight or get rid of unwanted body fat.

This article lists 12 foods that rev up your metabolism and help you lose weight.

1. Protein-Rich Foods

Protein-rich foods, such as meat, fish, eggs, dairy, legumes, nuts and seeds, could help increase your metabolism for a few hours.

They do so by requiring your body to use more energy to digest them.

This is known as the thermic effect of food (TEF). The TEF refers to the number of calories needed by your body to digest, absorb and process the nutrients in your meals.

Research shows that protein-rich foods increase TEF the most. For example, they increase your metabolic rate by 15–30 percent, compared to 5–10 percent for carbs and 0–3 percent for fats (1).

Protein-rich diets also reduce the drop in metabolism often seen during weight loss by helping your body hold on to its muscle mass (2, 3, 4, 5, 6, 7).

What's more, protein may also help keep you fuller for longer, which can prevent overeating (8, 9, 10, 11).

Bottom Line: Protein-rich foods can help boost your metabolism, maintain muscle mass and prevent you from overeating.

2. Iron, Zinc and Selenium-Rich Foods

Iron, zinc and selenium each play different but equally important roles in the proper function of your body.

However, they do have one thing in common: all three are required for the proper function of your thyroid gland, which regulates your metabolism (12).

Research shows that a diet too low in iron, zinc or selenium may reduce the ability of your thyroid gland to produce sufficient amounts of hormones. This can slow down your metabolism (13, 14, 15).

To help your thyroid function to the best of its ability, include zinc, selenium and iron-rich foods like meat, seafood, legumes, nuts and seeds in your daily menu.

Bottom Line: Foods rich in iron, zinc and selenium promote the proper function of your thyroid, which helps maintain a healthy metabolism.

3. Chili Peppers

Capsaicin, a chemical found in chili peppers, may boost your metabolism by increasing the number of calories and fat you burn.

In fact, a review of 20 research studies reports that capsaicin can help your body burn around 50 extra calories per day (16).

This effect was initially observed after taking 135–150 mg of capsaicin per day, but some studies report similar benefits with doses as low as 9–10 mg per day (17, 18, 19, 20).

Moreover, capsaicin may have appetite-reducing properties.

According to a recent study, consuming 2 mg of capsaicin directly before each meal seems to reduce the number of calories consumed, especially from carbs (21).

That said, not all studies agree on capsaicin's metabolism-boosting abilities (22, 23).

Bottom Line: Capsaicin, a compound found in chili peppers, may help slightly increase metabolism and fat oxidation.

4. Coffee

Studies report that the caffeine found in coffee can help increase metabolic rate by up to 11 percent (24, 25).

In fact, six different studies found that people who consume at least 270 mg of caffeine daily or the equivalent of about three cups of coffee, burn an extra 100 calories per day (26).

Furthermore, caffeine may also help your body burn fat for energy and seems especially effective at boosting your workout performance (27, 28, 29, 30).

However, its effects seem to vary from person to person, based on individual characteristics such as body weight and age (31, 32).

Bottom Line: The caffeine found in coffee may help boost the amount of calories and fat your body burns. However, its effects may vary by individual.

5. Tea

According to research, the combination of caffeine and catechins that's found in tea may work to boost your metabolism.

In particular, both oolong and green tea may increase metabolism by 4–10 percent. This could add up to burning an extra 100 calories per day (26, 33, 34, 35, 36, 37, 38).

In addition, oolong and green teas may help your body use stored fat for energy more effectively, increasing your fat-burning ability by up to 17 percent (35, 36, 37, 38, 39).

Nevertheless, as is the case with coffee, effects may vary from person to person.

Bottom Line: The combination of caffeine and catechins found in tea may help your body burn slightly more calories and fat each day.

6. Legumes and Pulses

Legumes and pulses, such as lentils, peas, chickpeas, beans and peanuts, are particularly high in protein compared to other plant foods.

Studies suggest that their high protein content requires your body to burn a greater number of calories to digest them, compared to lower-protein foods (40, 41).

Legumes also contain a good amount of dietary fiber, such as resistant starch and soluble fiber, which your body can use to feed the good bacteria living in your intestines (42, 43, 44).

In turn, these friendly bacteria produce short-chain fatty acids, which may help your body use stored fat as energy and maintain normal blood sugar levels (45, 46, 47).

In one study, humans consuming a legume-rich diet for eight weeks experienced beneficial changes in metabolism and lost 1.5 times more weight than the control group (48).

Legumes are also high in arginine, an amino acid that may increase the amount of carbs and fat your body can burn for energy (49).

In addition, peas, faba beans and lentils also contain substantial amounts of the amino acid glutamine, which may help increase the number of calories burned during digestion (50, 51).

Bottom Line: Legumes and pulses are high in protein, fiber and certain amino acids, which are thought to have metabolism-boosting properties.

7. Metabolism-Boosting Spices

Certain spices are thought to have particularly beneficial metabolism-boosting properties.

For instance, research shows that dissolving 2 grams of ginger powder in hot water and drinking it with a meal may help you burn up to 43 more calories than drinking hot water alone (52).

This hot ginger drink also seems to decrease levels of hunger and enhance feelings of satiety (53).

Grains of paradise, another spice in the ginger family, may have similar effects.

A recent study reported that participants given a 40-mg extract of grains of paradise burned 43 more calories in the following two hours than those given a placebo (54).

That said, researchers also noted that part of the participants were non-responders, so the effects may vary from one person to another.

Similarly, adding cayenne pepper to your meal may increase the amount of fat your body burns for energy, especially following a high-fat meal (55, 56).

However, this fat-burning effect may only apply to people unaccustomed to consuming spicy foods (56).

Bottom Line: Ginger, grains of paradise and cayenne pepper may help your body burn more calories or fat. However, effects can vary from one individual to another.

8. Cacao

Cacao and cocoa are tasty treats that may also benefit your metabolism.

For instance, studies in mice found that cocoa and cocoa extracts may promote the expression of genes that stimulate the use of fat for energy. This seems especially true in mice fed high-fat or high-calorie diets (57, 58, 59).

Interestingly, one study suggests that cocoa may prevent the action of enzymes necessary to break down fat and carbs during digestion (60).

In doing so, cocoa could theoretically play a role in preventing weight gain by reducing the absorption of some calories (60).

However, human studies examining the effects of cocoa, cacao or cacao products such as dark chocolate are rare. More studies are needed before strong conclusions can be made (61).

If you'd like to give cacao a try, opt for raw versions, as processing tends to reduce the amounts of beneficial compounds (62).

Bottom Line: Cacao may have certain metabolism-boosting properties, especially for those consuming high-calorie, high-fat diets.

9. Apple Cider Vinegar

Apple cider vinegar may increase your metabolism.

Several animal studies have shown vinegar to be particularly helpful in increasing the amount of fat burned for energy.

In one study, mice given vinegar experienced an increase in the AMPK enzyme, which prompts the body to decrease fat storage and increase fat burning (63).

In another study, obese rats treated with vinegar experienced an increase in the expression of certain genes, leading to reduced liver fat and belly fat storage (64, 65).

Apple cider vinegar is often claimed to boost metabolism in humans, but few studies have investigated the matter directly.

Nevertheless, apple cider vinegar may still help you lose weight in other ways, such as slowing stomach emptying and enhancing feelings of fullness (66, 67, 68, 69).

One study in humans even showed that participants given four teaspoons (20 ml) of apple cider vinegar ate up to 275 fewer calories over the rest of the day (70).

If you'd like to give apple cider vinegar a try, be careful to limit your daily consumption to two tablespoons (30 ml).

Also, make sure to read this article to reduce the risk of negative side effects.

Bottom Line: More studies are needed to confirm apple cider vinegar's metabolism-boosting properties in humans. That being said, it may aid weight loss in other ways.

10. Coconut Oil

Coconut oil is experiencing a surge in popularity.

That may be partly because coconut oil is high in medium-chain triglycerides (MCTs). This is contrary to most other types of fats, which usually contain higher amounts of long-chain fatty acids.

Unlike long-chain fats, once MCTs are absorbed, they go directly to the liver to be turned into energy. This makes them less likely to be stored as fat.

Interestingly, several studies show that MCTs can increase metabolic rate more than longer-chain fats (71, 72, 73, 74, 75, 76).

In addition, researchers report that a daily intake of 30 ml of coconut oil may successfully reduce waist size in obese individuals (77, 78).

Bottom Line: Replacing other fats with a small amount of coconut oil may boost your metabolism and help your body get rid of belly fat.

11. Water

Drinking enough water is a great way to stay hydrated.

Additionally, it seems that drinking water may also temporarily boost metabolism by 24–30 percent (79, 80, 81, 82).

Researchers note that about 40 percent of that increase may come from your body trying to match the water's temperature to its own (82).

Yet, the effects only seem to last for 60–90 minutes after drinking it and may vary from one person to another (83).

Bottom Line: Drinking water may temporarily increase your metabolism. However, effects are temporary and may vary between individuals.

12. Seaweed

Seaweed is a great source of iodine, a mineral required for the production of thyroid hormones and proper function of your thyroid gland (84).

Thyroid hormones have various functions, one of which is to regulate your metabolic rate (12).

Regularly consuming seaweed can help you meet your iodine needs and keep your metabolism revving at a high rate.

The reference daily intake of iodine for adults is 150 mcg per day. This can be met by consuming several servings of seaweed per week.

Although, some types of seaweed such as kelp are extremely high in iodine and should not be consumed in large amounts.

Fucoxanthin is another compound found in some varieties of seaweed that may help with metabolism.

It's primarily found in brown seaweed varieties and may have anti-obesity effects by increasing the amount of calories you burn (85).

Bottom Line: Certain compounds in seaweed may help prevent your metabolism from slowing down.

13. Anything Else?

Certain foods may help slightly increase your metabolism. Therefore, consuming them regularly may help you lose weight and keep it off in the long term.

However, foods are not the only way to boost your metabolism. Check out this article here for additional ways to help your body burn more calories each day.

Reposted with permission from our media associate Authority Nutrition.

By Franziska Spritzler

Keeping your metabolism high is crucial for losing weight and keeping it off.

Unfortunately, there are several common lifestyle mistakes that may be slowing down your metabolism.

Doing these on a regular basis could make it hard to lose weight and make you more prone to weight gain in the future.

Here are six lifestyle mistakes that can slow down your metabolism.

1. Eating Too Few Calories

Eating too few calories can cause a major decrease in metabolism.

Although a calorie deficit is needed for weight loss, it can be counterproductive for your calorie intake to drop too low.

When you dramatically lower your calorie intake, your body senses that food is scarce and lowers the rate at which it burns calories.

Controlled studies on lean and overweight people have confirmed that consuming less than 1,000 calories per day can have a significant impact on your metabolic rate (1, 2, 3, 4, 5).

Most studies measure resting metabolic rate, which is the number of calories burned during rest. However, some also measure calories burned during rest and activity over 24 hours, which is referred to as total daily energy expenditure.

In one study, when obese women ate 420 calories per day for four to six months, their resting metabolic rates slowed down significantly.

What's more, even after they increased their calorie intake over the following five weeks, their resting metabolic rates remained much lower than before the diet (3).

In another study, overweight people were asked to consume 890 calories per day. After three months, the total number of calories they burned per day was found to have dropped by 633 calories, on average (4).

It appears that even when calorie restriction is more moderate, it can slow metabolism somewhat.

In a four-day study of 32 people, the resting metabolic rate of people who ate 1,114 calories per day slowed more than twice as much as of those who consumed 1,462 calories daily. However, weight loss was similar for both groups (5).

If you're going to lose weight by calorie restriction, then don't restrict your calorie intake too much or for too long.

Bottom Line: Cutting calories too much and for too long lowers metabolic rate, which can make weight loss and weight maintenance more difficult.

2. Skimping on Protein

Eating enough protein is extremely important for achieving and maintaining a healthy weight.

Studies have shown that, in addition to helping you feel full, a high protein intake can significantly increase the rate at which your body burns calories (6, 7, 8).

The increase in metabolism that occurs after digestion is called the thermic effect of food.

The thermic effect of protein is much higher than the thermic effects of carbs or fat. Indeed, eating protein has been observed to temporarily increase metabolism by about 20–30 percent, versus 5–10 percent for carbs and 3 percent or less for fat (9).

Although metabolic rate inevitably slows during weight loss and continues to be slower during weight maintenance, there's evidence that higher protein intake can minimize this effect.

In one study, participants followed one of three diets in an effort to maintain a 10–15 percent weight loss.

The diet highest in protein reduced participants' total daily energy expenditure by only 97 calories, versus a decrease of 297–423 calories in people who consumed less protein (10).

Another study found that people needed to eat at least 0.5 grams of protein per pound (1.2 grams/kg) of their body weight in order to prevent their metabolism from slowing during and after weight loss (11).

Bottom Line: Protein increases metabolic rate more than carbs or fat. Increased protein intake helps preserve metabolic rate during weight loss and maintenance.

3. Leading a Sedentary Lifestyle

Being sedentary may lead to a significant decrease in the number of calories you burn every day.

Unfortunately, many people have lifestyles that mainly involve sitting at work, which can have negative effects on metabolic rate and overall health (12).

Although working out or playing sports can have a major impact on the number of calories you burn, even basic physical activity such as standing up, cleaning and taking the stairs can help you burn calories.

This type of activity is referred to as non-exercise activity thermogenesis (NEAT).

One study found that performing a high amount of NEAT regularly could burn up to 2,000 additional calories per day. However, such a dramatic increase is not realistic for most people (13).

Another study found that watching TV while you're sitting burns an average of 8 percent fewer calories than typing while you're sitting and an average of 16 percent fewer calories than standing (14).

Working at a standing desk or simply getting up to walk around several times per day can help increase your NEAT and prevent your metabolism from dropping.

Bottom Line: Being inactive reduces the number of calories you burn during the day. Try to minimize sitting and increase your general activity levels.

4. Not Getting Enough High-Quality Sleep

Sleep is extremely important for good health.

Sleeping fewer hours than you need may increase your risk of a number of diseases, including heart disease, diabetes and depression (15).

Several studies have found that inadequate sleep may also lower your metabolic rate and increase your likelihood of weight gain (16, 17, 18).

One study found that healthy adults who slept four hours per night for five nights in a row experienced a 2.6 percent decrease in resting metabolic rate, on average.

Participants' resting metabolic rate returned to normal following 12 hours of uninterrupted sleep (17).

Lack of sleep is made worse by sleeping during the day instead of at night. This sleep pattern disrupts your body's circadian rhythms, the biological changes in your body that occur in response to light and darkness over a 24-hour cycle.

A five-week study found that prolonged sleep restriction combined with circadian rhythm disruption significantly decreased participants' resting metabolic rate by an average of 8 percent (18).

Bottom Line: Getting adequate, high-quality sleep and sleeping at night rather than during the day can help preserve your metabolic rate.

5. Drinking Sugary Beverages

Sugar-sweetened drinks are the absolute worst beverages for health.

A high consumption of sodas and other sugary drinks has been linked to all sorts of health problems, including insulin resistance, diabetes and obesity (19, 20).

Most of the negative effects of sugar-sweetened beverages can be attributed to fructose. Table sugar contains 50 percent fructose, while high-fructose corn syrup contains 55 percent fructose.

Results from a 2012 study suggest that frequently consuming sugar-sweetened beverages may slow down your metabolism.

In this 12-week controlled study, overweight and obese people who consumed 25 percent of their calories as fructose-sweetened beverages on a weight-maintaining diet experienced a significant drop in metabolic rate (21).

Unfortunately, there aren't many studies that have measured how metabolic rate is affected by a high intake of sugar-sweetened beverages.

However, research in animals and humans has shown that excessive fructose consumption promotes increased fat storage in the belly and liver (22, 23, 24, 25, 26).

Bottom Line: A high intake of fructose-containing beverages has been found to reduce metabolic rate and promote fat storage in the belly and liver.

6. A Lack of Resistance Training

Working out with weights is a great strategy to keep your metabolism from slowing down.

Strength training has been shown to increase metabolic rate in healthy people, as well as those who have heart disease or are overweight or obese (27, 28, 29, 30).

Resistance training increases muscle mass, which makes up much of the fat-free mass in your body. Having a higher amount of fat-free mass significantly increases the number of calories you burn at rest (31, 32, 33).

Fortunately, doing even minimal amounts of strength training appears to boost energy expenditure.

In a six-month study, people who performed resistance training for 11 minutes per day for three days a week experienced a 7.4 percent increase in resting metabolic rate and burned 125 extra calories per day, on average (34).

In contrast, not doing any strength training can cause your metabolic rate to decline, especially during weight loss and as you get older (31, 35, 36).

Bottom Line: Resistance training increases muscle mass and helps preserve metabolic rate during weight loss and aging.

Take Home Message

Engaging in lifestyle behaviors that slow down your metabolism can lead to weight gain over time. It's best to avoid or minimize them as much as possible.

Fortunately, there are also many things that can boost your metabolism to help you lose weight and keep it off.

Reposted with permission from our media associate Authority Nutrition.

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