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Some surprising truths about matabolism

We imagine our metabolism as a fire, flaming up when we exercise to torch calories. But that’s just a very small fraction of what it does, according to Herman Pontzer, Ph.D., an evolutionary anthropologist at Duke University, the author of Burn: The Misunderstood Science of Metabolism, and the principal investigator for a game-changing new study on metabolism.

“Metabolism is the work your cells do every minute of every day,” says Pontzer. “You’ve got 37 million of them, and each cell is like a little factory churning out everything needed to keep your body functioning.” Some calories do get burned during exercise, but most of what you eat is used to fuel the continuous work your cells do.

The new research, published in Science by Pontzer and more than 80 coauthors, looked at metabolism more precisely than had ever been done before. It measured metabolism in almost 6,500 people around the world, from newborns to 95-year-olds. Once the scientists controlled for variables that affect energy expenditure, like a person’s body size and percentage of fat, they got “a clear road map of metabolism over our life span,” says Pontzer.

METABOLISM DOESN’T SLOW DOWN IN MIDLIFE

For years we’ve heard that our metabolism peaks when we’re teenagers and slows significantly as we approach middle age. But the researchers discovered that metabolism crests far earlier and declines much later, and that it has four distinct stages.

Metabolism is at its highest during infancy, and a baby’s metabolic rate is 50 percent higher than an adult’s. From ages 1 to 20, metabolism drops about 3 percent a year. Then, from ages 20 to 60, metabolism holds steady. After age 60, it slowly starts to decline (0.7 percent a year). That means for 40 years we’re burning calories at a steady rate, about 2,500 a day on average, says Pontzer. And a 60-year-old has the same metabolism as a 20-year-old!

MEN DON’T HAVE A BETTER METABOLISM

“There’s nothing special about the male metabolism,” says Pontzer. “Men tend to be bigger, and their bodies consist of more lean muscle and less fat.” Muscle uses more energy than fat, which accounts for the difference (the reason he can lose a pound faster than you can). The scientists controlled for these factors and found no difference in metabolic rate.

MILESTONES DON’T CHANGE METABOLISM

It’s a myth that pregnancy and menopause make a big difference. “These major metabolic milestones didn’t affect metabolic rate,” says Jennifer Rood, Ph.D., a coauthor of the study who specializes in research on metabolism and energy expenditure at Louisiana State University’s Pennington Biomedical Research Center. “That was a surprise. But it’s also encouraging. The fact that your rate remains steady through childbirth and into your 60s means you don’t have to work harder to maintain a healthy weight, as long as you follow a healthy diet and get the recommended amount of exercise and rest.”

HAVING MUSCLE HELPS

The types of cells you have affect the amount of work they do and the energy they burn, says Pontzer. “A cell in your fat is not as busy as a cell in your muscles,” he says. “If you have a lot of lean mass, you’re going to burn calories more efficiently than someone who has more fat mass.” That’s why exercise, particularly muscle-building strength training, can be beneficial.

Alas, a reality check: There is no proven way to boost metabolism, says Pontzer. But exercise and diet do make a difference. “Think of it this way: You’re burning a set number of calories each day, but you get to decide how to burn them,” says Pontzer. “If you expend them on exercise, you’re going to be a lot healthier and have less inflammation than someone who doesn’t. The same is true with food. You decide how to fuel your body. That’s where a healthy diet factors in.”

TIMING MEALS MATTERS

When the day begins to wind down, our body does the opposite—cranking up to be at its calorie-burning peak, according to a study published in Current Biology. “We discovered that you naturally burn about 10 percent more calories in the late afternoon than you do later at night,” says Kirsi-Marja Zitting, Ph.D., an associate neuroscientist at Brigham and Women’s Hospital in Boston, an instructor at Harvard Medical School, and the lead author of the study. That’s about 130 calories that your body is torching without any extra effort on your part.

Researchers suspect that metabolism ebbs and flows according to our circadian rhythms. At night, when we’re asleep, our systems are expending less energy, so our metabolic rate slows. Eat in those wee hours, as night shift workers do, and your body isn’t able to burn off the calories, which could eventually lead to weight gain, says Zitting. During the day, when we’re naturally active, our metabolism rises, until it crests around 5 p.m. “Previous research has shown that hunger spikes in the afternoon as well,” says Zitting. “Since that’s also when we’re burning the most calories, it makes sense that we’re hungriest then, too. Our bodies may be tuned to a late-in-the-day rhythm.”

Syncing our diets to our internal clocks can have health benefits. For general well-being, the most important thing is to maintain a regular schedule, says Zitting. “Wake up and go to bed around the same time every day,” she advises, “and have breakfast, lunch, and dinner at about the same hours as well.” Your body is primed to do things at certain times. Throw its agenda out of whack, and your sleep, health, and weight can suffer.

Also, avoid eating at extreme hours. Let’s say you get home from work at 10 p.m. Don’t consume a big meal then because your body is in slowdown mode and is less likely to burn it off, says Zitting. Instead, have a healthy dinner earlier, before you leave work.

Finally, it may help to eat your carbs early in the day and foods higher in fat at night. “Our research found that you are more prone to burn carbohydrates in the morning and lipids [aka fats] in the evening,” says Zitting. “The difference was small, but it was significant.”

Most Olympic marathoners spend their youth focused on running. They join track clubs, compete in national championships, and pursue the sport from an early age.

Julia Mayer’s journey was very different.

Today, Mayer is Austria’s marathon record holder, a multiple national record holder on the roads, and an Olympian. Yet for much of her athletic life, running was not her primary sport.

For 16 years, she played soccer.

Then she discovered something that would change her life.

“I noticed that I was really fast in the fun runs and that it was really, really fun,” Mayer said when reflecting on her transition from soccer to distance running.

What began as curiosity quickly became a passion. She eventually made the bold decision to leave soccer behind and focus entirely on running. It was a move that surprised many people around her, but Mayer believed she had found her true athletic calling.

The decision proved to be the right one.

Within a few years, Mayer developed into one of Europe’s top marathon runners. Her steady improvement carried her from local races to the international stage, where she began rewriting Austria’s record books.

She now holds Austrian records in the marathon, half marathon, and road 10K. Her marathon best of 2:26:08 established her as the fastest female marathoner in Austrian history. Her performances in the half marathon and 10K have further cemented her place among the country’s all-time great distance runners.

Her rise culminated with qualification for the 2024 Olympic Games in Paris.

Competing in the Olympic marathon represented the realization of a dream. On one of the most challenging marathon courses ever used for the Olympics, Mayer ran courageously against the strongest field in the world and finished 55th in her Olympic debut.

Behind the scenes, success has come through extraordinary dedication. During marathon preparation, Mayer trains twice a day and covers approximately 200 kilometers, or 124 miles, each week. The workload demands discipline, patience, and a deep commitment to continuous improvement. 

What makes her story especially inspiring is not simply the records or the Olympic appearance.

It is the fact that she found her greatest talent later than many elite runners.

In a sport where athletes are often identified at a young age, Mayer’s journey serves as a reminder that potential does not always reveal itself early. Sometimes it takes years of experience, a willingness to try something new, and the courage to follow a different path. 

The former soccer player who once chased a ball across a field is now chasing history on the roads of Europe.

And according to those closest to her, her best performances may still be ahead.

For runners of every age and ability, Julia Mayer’s story delivers a powerful lesson: it is never too late to discover what you are capable of.

From soccer player to Olympian, her journey proves that remarkable achievements can begin when least expected.

Megan Keith produced the performance of her career in Oslo on Thursday night, shattering one of Scotland’s longest-standing distance running records and cementing her place among Britain’s greatest female 3000m runners.

The 24-year-old clocked a sensational 8:28.35 over 3000m, breaking the Scottish outdoor record that had stood for nearly four decades. In doing so, Keith eclipsed the previous mark of 8:29.02, set by Scottish legend Yvonne Murray back in 1988, ending a record reign that had lasted 38 years.

Keith’s breakthrough run was more than just a national record. The performance also propelled her to third on the UK outdoor all-time list, placing her behind only two of Britain’s most celebrated distance runners — Paula Radcliffe, who leads the rankings with 8:22.20, and Laura Weightman, whose 8:26.07 remains the second-fastest outdoor mark by a British woman.

The significance of Keith’s achievement is amplified by the calibre of athletes she now joins in the record books. For decades, Murray’s mark stood as one of Scottish athletics’ most untouchable records, surviving generations of elite competitors. Keith has now succeeded where many outstanding runners have fallen short, announcing herself as one of the leading distance talents in British athletics.

Her time also compares favourably with the best performances produced indoors. Olympic medallist Laura Muir ran 8:26.41 indoors in Karlsruhe in 2017, underlining just how exceptional Keith’s outdoor effort in Oslo truly was.

The run continues a remarkable rise for the Scottish star, whose progression over recent seasons has transformed her from a promising prospect into a genuine force on the international stage. Running with confidence and composure against elite competition, Keith demonstrated both the speed and endurance required to challenge the very best in Europe and beyond.

With the World Championship season gathering momentum, Keith’s record-breaking display sends a powerful message. Not only has she etched her name into Scottish athletics history, but she has also established herself as a serious contender in one of the sport’s most competitive events.

In Oslo, Megan Keith did far more than break a record. She ended a 38-year wait, climbed into the upper echelon of British distance running, and delivered a performance that may prove to be a defining moment in her career.

British middle-distance talent Phoebe Gill took another significant step forward in her return to top form, producing a determined victory over 800 metres at the Meeting de Marseille in France on Wednesday.

Competing in challenging, wind-affected conditions, the 19-year-old demonstrated both resilience and composure as she held off a late charge from Switzerland's Veronica Vancardo to secure the win in 2:00.81. Vancardo finished just three hundredths of a second behind in 2:00.84, underlining the fiercely contested nature of the race.

While the margin of victory was narrow, the result represented another encouraging milestone for Gill as she continues to rebuild momentum following her injury setback. The young Briton showed impressive race awareness and strength in the closing stages, maintaining her advantage despite the difficult conditions that made fast running a challenge throughout the evening.

The Marseille triumph adds to a growing body of evidence that Gill is steadily progressing toward her best form. Earlier in her comeback campaign, she clocked 2:01.50 for 800m in Bydgoszcz before demonstrating her versatility with a strong 4:05.53 performance over 1500 metres at the BMC Grand Prix meeting in Trafford.

Those performances have highlighted not only her improving fitness but also her ability to compete across multiple distances as she carefully builds her season. The Marseille victory now provides further confirmation that the European junior star is moving in the right direction.

Gill emerged as one of Britain's most exciting middle-distance prospects through a series of breakthrough performances as a teenager, earning widespread recognition for her fearless racing style and remarkable maturity. Injury temporarily interrupted that upward trajectory, but her recent results suggest she is steadily rediscovering the form that made her one of the sport's brightest young talents.

With each race, the signs of progress become increasingly evident. Winning in difficult conditions and under pressure from a quality field is often a stronger indicator than a fast time alone, and Gill's latest success demonstrated exactly those qualities.

As the summer season gathers pace, the Marseille victory offers another confidence boost for the British teenager, whose return continues to gain momentum. If her recent progression is any indication, Gill could soon find herself back among the leading names on the European middle-distance circuit. 

The NCAA Track and Field Championships delivered a moment few could have predicted as Ja’Kobe Tharp produced one of the most astonishing performances in the history of sprint hurdling, rewriting the record books in spectacular fashion.

Competing in the opening round of the men’s 110-meter hurdles, the Auburn star stunned the athletics world by clocking an incredible 12.75 seconds, becoming the first athlete ever to break the 12.80-second barrier. In doing so, he eclipsed the long-standing world record of 12.80 set by Aries Merritt in 2012, a mark that had stood as one of the sport’s most revered achievements for more than a decade.

What makes Tharp’s breakthrough even more remarkable is the scale of his improvement. Entering the championships, the defending NCAA and U.S. champion had recorded a season-best of 13.05 seconds. Yet under the brightest spotlight, he unleashed a performance that exceeded every expectation, slicing an extraordinary 0.26 seconds from his personal best in a race that instantly became one of the greatest ever run.

The achievement sent shockwaves throughout the track and field community. While Tharp arrived in Eugene as one of the leading contenders for the NCAA title, few envisioned a performance capable of redefining the limits of the event. Instead, the American hurdler delivered a race for the ages, combining flawless technique, explosive speed, and impeccable rhythm from the first hurdle to the finish line.

The historic run not only secured his place in athletics history but also transformed the outlook of the championship. With the world record now in his possession, Tharp advances to the final as the overwhelming favorite, carrying momentum that could make an already unforgettable weekend even more extraordinary.

For years, the 12.80 barrier appeared untouchable. On a stunning day at the NCAA Championships, Ja’Kobe Tharp proved otherwise, producing the kind of performance that reminds fans why sport remains so unpredictable. In a matter of seconds, he turned a routine qualifying round into a landmark moment that will be remembered for generations.

The world record no one saw coming is now a reality—and Ja’Kobe Tharp is the man who changed history.

A new chapter in middle-distance running may have begun in Oslo after American teenager Cooper Lutkenhaus produced one of the most remarkable performances of the season, narrowly defeating reigning Olympic champion Emmanuel Wanyonyi in a thrilling men's 800m contest at the Diamond League meeting.

The 17-year-old sensation shocked a world-class field by crossing the finish line first in a race that came down to the smallest of margins. After an intense battle over the final metres, Lutkenhaus held off Wanyonyi by just one hundredth of a second, producing a dramatic finish that left the packed stadium in disbelief.

From the opening lap, the pace was relentless as the leading contenders positioned themselves for a fierce showdown. As the athletes entered the home straight, Wanyonyi appeared poised to unleash his trademark finishing kick. However, Lutkenhaus refused to be intimidated, matching the Olympic champion stride for stride before producing a perfectly timed lean at the line to secure a historic victory.

The result marks a breakthrough moment for the young American, who continues to establish himself as one of the brightest talents in global athletics. Defeating an Olympic champion at a Diamond League event is a feat many athletes spend entire careers pursuing, yet Lutkenhaus achieved it before reaching adulthood.

For Wanyonyi, the narrow defeat does little to diminish his status as one of the world's premier 800m runners. The Kenyan once again demonstrated his exceptional class and competitiveness, pushing the race to a world-class standard and forcing his young rival to deliver the performance of a lifetime.

Beyond the result itself, the race offered a glimpse into what could become one of the sport's most exciting rivalries in the years ahead. With established stars and emerging talents now pushing each other to new heights, the men's 800m continues to evolve into one of athletics' most captivating events.

On a memorable night in Oslo, the spotlight belonged to Cooper Lutkenhaus. At just 17 years old, he stood toe-to-toe with an Olympic champion and emerged victorious, announcing himself to the athletics world in spectacular fashion.