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Scientists Say Walking Burns More Calories Than Previously Thought

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Step-counters, rejoice: physiologists have found that the equations used for calculating energy expenditure are inaccurate, and say we’re likely burning more calories walking than we realized. They published their report in the Journal of Applied Physiology. 

Today, most programs use one of two methods to estimate calories burned by walkers: the ACSM (for the American College of Sports Medicine) and the Pandolf, which was invented by the military. These equations are about 40 years old, which is reason enough to test them again. They were also developed using just a few adult men of average height, and if we’ve learned anything in the last few years, it’s that a small group of adult men cannot be used as a stand-in for the entire population.

So Southern Methodist University (SMU) physiologists Lindsay Ludlow and Peter Weyand decided it was time to put these formulas to the test. "Burning calories is of major importance to health, fitness and the body's physiological status," Weyand said in a press statement. "But it hasn't been really clear just how accurate the existing standards are under level conditions because previous assessments by other researchers were more limited in scope." 

The researchers built a database of existing data in the scientific literature. With this data, they could compare the ACSM, Pandolf, and other standard equations. They found that for people walking on firm, level ground, both the ACSM and Pandolf underestimated calories burned in 97 percent of the cases examined by researchers. Clearly, a new equation was in order. 

Ludlow and Weyand set out to create an algorithm that would work for anyone. "The SMU approach improves upon the existing standards by including different-sized individuals and drawing on a larger database for equation formulation," Weyand said. 

Dr. Ludlow monitors a colleague during a treadmill test. Image Credit: Hillsman Jackson, SMU

If you want to play along at home (in your ... home physiology lab), here’s what they came up with:

(VO2 is oxygen consumption and Ht is height measured in meters.)

Ludlow said their equation should apply “…regardless of the height, weight, and speed of the walker. And it’s appreciably more accurate.”  

A lot more accurate, in fact (not that that’s a high bar). The new equation is four times more accurate when used to calculate energy expenditure of a mixed group of adults and kids. For adults alone, it’s still two to three times more accurate than the old formulas. 

Accurate accounting of energy expenditure is important for more than just casual walkers. Once a person’s estimated calorie-burn rate has been established, the formula can be used to predict how much energy that person will use—and therefore how much they will need—for a certain task. Such an algorithm could be useful for athletes in training, but also for military operations, in which the need for physiological efficiency is at a premium.

"These soldiers carry incredible loadsup to 150 pounds, but they often need to be mobile to successfully carry out their missions," Weyand said. In other words, they've got to be taking in enough calories to get the job done.

As yet, the formula has only been tested for walkers on solid, flat ground. The researchers’ next step is to expand the algorithm to calculate calorie burning on hills. 

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Food
New Plant-Based Coating Can Keep Your Avocados Fresh for Twice as Long
Apeel
Apeel

Thanks to a food technology startup called Apeel Sciences, eating fresh avocados will soon be a lot easier. The Bill Gates–backed company has developed a coating designed to keep avocados fresh for up to twice as long as traditional fruit, Bloomberg reports, and these long-lasting avocados will soon be available at 100 grocery stores across the Midwestern U.S. Thirty or so of the grocery stores involved in the limited rollout of the Apeel avocado will be Costcos, so feel free to buy in bulk.

Getting an avocado to a U.S. grocery store is more complicated than it sounds; the majority of avocados sold in the U.S. come from California or Mexico, making it tricky to get fruit to the Midwest or New England at just the right moment in an avocado’s life cycle.

Apeel’s coating is made of plant material—lipids and glycerolipids derived from peels, seeds, and pulp—that acts as an extra layer of protective peel on the fruit, keeping water in and oxygen out, and thus reducing spoilage. (Oxidation is the reason that your sliced avocados and apples brown after they’ve been exposed to the air for a while.) The tasteless coating comes in a powder that fruit producers mix with water and then dip their fruit into.

A side-by-side comparison of a coated and uncoated avocado after 30 days, with the uncoated avocado looking spoiled and the coated one looking fresh
Apeel

According to Apeel, coating a piece of produce in this way can keep it fresh for two to three times longer than normal without any sort of refrigeration of preservatives. This not only allows consumers a few more days to make use of their produce before it goes bad, reducing food waste, but can allow producers to ship their goods to farther-away markets without refrigeration.

Avocados are the first of Apeel's fruits to make it to market, but there are plans to debut other Apeel-coated produce varieties in the future. The company has tested its technology on apples, artichokes, mangos, and several other fruits and vegetables.

[h/t Bloomberg]

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15 Facts About the Summer Solstice
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It's the longest day of the year in the Northern Hemisphere, so soak up some of those direct sunrays (safely, of course) and celebrate the start of summer with these solstice facts.

1. THIS YEAR IT'S JUNE 21.

June 21 date against a yellow background
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The summer solstice always occurs between June 20 and June 22, but because the calendar doesn't exactly reflect the Earth's rotation, the precise time shifts slightly each year. For 2018, the sun will reach its greatest height in the sky for the Northern Hemisphere on June 21 at 6:07 a.m. Eastern Time.

2. THE SUN WILL BE DIRECTLY OVERHEAD AT THE TROPIC OF CANCER.

A vintage mapped globe showing the Tropic of Cancer
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While the entire Northern Hemisphere will see its longest day of the year on the summer solstice, the sun is only directly overhead at the Tropic of Cancer (23 degrees 27 minutes north latitude).

3. THE NAME COMES FROM THE FACT THAT THE SUN APPEARS TO STAND STILL.

Stonehenge at sunrise.
CARL DE SOUZA, AFP/Getty Images

The term "solstice" is derived from the Latin words sol (sun) and sistere (to stand still), because the sun's relative position in the sky at noon does not appear to change much during the solstice and its surrounding days. The rest of the year, the Earth's tilt on its axis—roughly 23.5 degrees—causes the sun's path in the sky to rise and fall from one day to the next.

4. THE WORLD'S BIGGEST BONFIRE WAS PART OF A SOLSTICE CELEBRATION.

A large bonfire
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Celebrations have been held in conjunction with the solstice in cultures around the world for hundreds of years. Among these is Sankthans, or "Midsummer," which is celebrated on June 24 in Scandinavian countries. In 2016, the people of Ålesund, Norway, set a world record for the tallest bonfire with their 155.5-foot celebratory bonfire.

5. THE HOT WEATHER FOLLOWS THE SUN BY A FEW WEEKS.

Colorful picture of the sun hitting ocean waves.
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You may wonder why, if the solstice is the longest day of the year—and thus gets the most sunlight—the temperature usually doesn't reach its annual peak until a month or two later. It's because water, which makes up most of the Earth's surface, has a high specific heat, meaning it takes a while to both heat up and cool down. Because of this, the Earth's temperature takes about six weeks to catch up to the sun.

6. THOUSANDS OF PEOPLE GATHER AT STONEHENGE TO CELEBRATE.

Rollo Maughfling, the Archdruid of Glastonbury and Stonehenge, conducts a Solstice celebration service for revelers as they wait for the midsummer sunrise at Stonehenge on June 21, 2012, near Salisbury, England.
Rollo Maughfling, the Archdruid of Glastonbury and Stonehenge, conducts a Solstice celebration service for revelers as they wait for the midsummer sunrise at Stonehenge on June 21, 2012, near Salisbury, England.
Matt Cardy, Getty Images

People have long believed that Stonehenge was the site of ancient druid solstice celebrations because of the way the sun lines up with the stones on the winter and summer solstices. While there's no proven connection between Celtic solstice celebrations and Stonehenge, these days, thousands of modern pagans gather at the landmark to watch the sunrise on the solstice.

7. PAGANS CELEBRATE THE SOLSTICE WITH SYMBOLS OF FIRE AND WATER.

Arty image of fire and water colliding.
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In Paganism and Wicca, Midsummer is celebrated with a festival known as Litha. In ancient Europe, the festival involved rolling giant wheels lit on fire into bodies of water to symbolize the balance between fire and water.

8. IN ANCIENT EGYPT, THE SOLSTICE HERALDED THE NEW YEAR.

Stars in the night sky.
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In Ancient Egypt, the summer solstice preceded the appearance of the Sirius star, which the Egyptians believed was responsible for the annual flooding of the Nile that they relied upon for agriculture. Because of this, the Egyptian calendar was set so that the start of the year coincided with the appearance of Sirius, just after the solstice.

9. THE ANCIENT CHINESE HONORED THE YIN ON THE SOLSTICE.

Yin and yang symbol on textured sand.
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In ancient China, the summer solstice was the yin to the winter solstice's yang—literally. Throughout the year, the Chinese believed, the powers of yin and yang waxed and waned in reverse proportion to each other. At the summer solstice, the influence of yang was at its height, but the celebration centered on the impending switch to yin. At the winter solstice, the opposite switch was honored.

10. IN ALASKA, THE SOLSTICE IS CELEBRATED WITH A MIDNIGHT BASEBALL GAME.

Silhouette of a baseball player.
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Each year on the summer solstice, the Alaska Goldpanners of Fairbanks celebrate their status as the most northerly baseball team on the planet with a game that starts at 10:00 p.m. and stretches well into the following morning—without the need for artificial light—known as the Midnight Sun Game. The tradition originated in 1906 and was taken over by the Goldpanners in their first year of existence, 1960.

11. THE EARTH IS ACTUALLY AT ITS FARTHEST FROM THE SUN DURING THE SOLSTICE.

The Earth tilted on its axis.
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You might think that because the solstice occurs in summer that it means the Earth is closest to the sun in its elliptical revolution. However, the Earth is actually closest to the sun when the Northern Hemisphere experiences winter and is farthest away during the summer solstice. The warmth of summer comes exclusively from the tilt of the Earth's axis, and not from how close it is to the sun at any given time. 

12. IRONICALLY, THE SOLSTICE MARKS A DARK TIME IN SCIENCE HISTORY.

Galileo working on a book.
Hulton Archive, Getty Images

Legend has it that it was on the summer solstice in 1633 that Galileo was forced to recant his declaration that the Earth revolves around the Sun; even with doing so, he still spent the rest of his life under house arrest.

13. AN ALTERNATIVE CALENDAR HAD AN EXTRA MONTH NAMED AFTER THE SOLSTICE.

Pages of a calendar
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In 1902, a British railway system employee named Moses B. Cotsworth attempted to institute a new calendar system that would standardize the months into even four-week segments. To do so, he needed to add an extra month to the year. The additional month was inserted between June and July and named Sol because the summer solstice would always fall during this time. Despite Cotsworth's traveling campaign to promote his new calendar, it failed to catch on.

14. IN ANCIENT GREECE, THE SOLSTICE FESTIVAL MARKED A TIME OF SOCIAL EQUALITY.

Ancient Greek sculpture in stone.
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The Greek festival of Kronia, which honored Cronus, the god of agriculture, coincided with the solstice. The festival was distinguished from other annual feasts and celebrations in that slaves and freemen participated in the festivities as equals.

15. ANCIENT ROME HONORED THE GODDESS VESTA ON THE SOLSTICE.

Roman statue of a vestal virgin
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In Rome, midsummer coincided with the festival of Vestalia, which honored Vesta, the Roman goddess who guarded virginity and was considered the patron of the domestic sphere. On the first day of this festival, married women were allowed to enter the temple of the Vestal virgins, from which they were barred the rest of the year.

A version of this list originally ran in 2015.

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