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).
- Hormone disorders: Cushing's syndrome and hypothyroidism slow down metabolic rate and increase the risk of weight gain (9).
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.
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, 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.
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.
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By Katherine Kornei
Clear-cutting a forest is relatively easy—just pick a tree and start chopping. But there are benefits to more sophisticated forest management. One technique—which involves repeatedly harvesting smaller trees every 30 or so years but leaving an upper story of larger trees for longer periods (60, 90, or 120 years)—ensures a steady supply of both firewood and construction timber.
A Pattern in the Rings<p>The <a href="https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/coppice-standards-0" target="_blank">coppice-with-standards</a> management practice produces a two-story forest, said <a href="https://www.researchgate.net/profile/Bernhard_Muigg" target="_blank">Bernhard Muigg</a>, a dendrochronologist at the University of Freiburg in Germany. "You have an upper story of single trees that are allowed to grow for several understory generations."</p><p>That arrangement imprints a characteristic tree ring pattern in a forest's upper story trees (the "standards"): thick rings indicative of heavy growth, which show up at regular intervals as the surrounding smaller trees are cut down. "The trees are growing faster," said Muigg. "You can really see it with your naked eye."</p><p>Muigg and his collaborators characterized that <a href="https://ltrr.arizona.edu/about/treerings" target="_blank">dendrochronological pattern</a> in 161 oak trees growing in central Germany, one of the few remaining sites in Europe with actively managed coppice-with-standards forests. They found up to nine cycles of heavy growth in the trees, the oldest of which was planted in 1761. The researchers then turned to a historical data set — more than 2,000 oak <a href="https://eos.org/articles/podcast-discovering-europes-history-through-its-timbers" target="_blank" rel="noopener noreferrer">timbers from buildings and archaeological sites</a> in Germany and France dating from between 300 and 2015 — to look for a similar pattern.</p>
A Gap of 500 Years<p>The team found wood with the characteristic coppice-with-standards tree ring pattern dating to as early as the 6th century. That was a surprise, Muigg and his colleagues concluded, because the first mention of this forest management practice in historical documents occurred only roughly 500 years later, in the 13th century.</p><p>It's probable that forest management practices were not well documented prior to the High Middle Ages (1000–1250), the researchers suggested. "Forests are mainly mentioned in the context of royal hunting interests or donations," said Muigg. Dendrochronological studies are particularly important because they can reveal information not captured by a sparse historical record, he added.</p><p>These results were <a href="https://www.nature.com/articles/s41598-020-78933-8" target="_blank">published in December in <em>Scientific Reports</em></a>.</p><p>"It's nice to see the longevity and the history of coppice-with-standards," said <a href="https://www.teagasc.ie/contact/staff-directory/s/ian-short/" target="_blank">Ian Short</a>, a forestry researcher at Teagasc, the Agriculture and Food Development Authority in Ireland, not involved in the research. This technique is valuable because it promotes conservation and habitat biodiversity, Short said. "In the next 10 or 20 years, I think we'll see more coppice-with-standards coming back into production."</p><p>In the future, Muigg and his collaborators hope to analyze a larger sample of historic timbers to trace how the coppice-with-standards practice spread throughout Europe. It will be interesting to understand where this technique originated and how it propagated, said Muigg, and there are plenty of old pieces of wood waiting to be analyzed. "There [are] tons of dendrochronological data."</p><p><em><a href="mailto:email@example.com" target="_blank" rel="noopener noreferrer">Katherine Kornei</a> is a freelance science journalist covering Earth and space science. Her bylines frequently appear in Eos, Science, and The New York Times. Katherine holds a Ph.D. in astronomy from the University of California, Los Angeles.</em></p><p><em>This story originally appeared in <a href="https://eos.org/articles/tree-rings-reveal-how-ancient-forests-were-managed" target="_blank">Eos</a></em> <em>and is republished here as part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story.</em></p>
Earth's ice is melting 57 percent faster than in the 1990s and the world has lost more than 28 trillion tons of ice since 1994, research published Monday in The Cryosphere shows.
By Jewel Fraser
Noreen Nunez lives in a middle-class neighborhood that rises up a hillside in Trinidad's Tunapuna-Piarco region.