How Obesity Fuels Inactivity

 

Women jogging in Central Park New York

Credit: iStock

More than one in three adults and one in six children in the U.S. are obese. Obesity—defined as a serious degree of overweight—is a leading cause of death, disease and disability. Although obesity has been linked to genetic disorders, it is most often caused by unhealthy behaviors and, therefore, is preventable and reversible.

Throughout the day, we get calories from food and we burn the calories off when we move our bodies. When we eat more calories than we burn, our bodies store the excess calories as fat, which accumulates over time. Eating too many calories and not moving enough are two factors that can cause obesity. Only one in five adults in the U.S. meets minimum physical activity recommendations, making physical inactivity a significant contributor to obesity. People who are overweight need to eat fewer calories and/or increase physical activity to lose excess fat. These lifestyle changes are often challenging, and may be compounded by the fact that exercise may be harder to do when you’re obese.

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 The cycle of obesity. Credit: Kim Henige

Carrying excess body weight can make joint pain more likely, which makes physical activity more difficult. Now, researchers may have discovered another reason excess body weight makes physical activity more difficult. A recent study published in the Journal of Applied Physiology shows that the working muscles of obese mice tired out more quickly than those of lean mice. These findings support a cycle of obesity where inactivity leads to obesity, which leads to more inactivity. Breaking the negative cycle of obesity and re-establishing a healthy body weight is possible, but takes considerable dedication and persistence to overcome the barriers and discomfort of the process.

Remember that the path to a healthier weight starts by taking a step! Visit the Centers for Disease Control and Prevention website for weight loss strategies, success stories of people who’ve lost weight and kept it off and more.

Kim HenigeKim Henige, EdD, CSCS, ACSM EP-C, is an associate professor and undergraduate program coordinator in the department of kinesiology at California State University, Northridge.

Microvesicles and Blood Vessels and Exercise, Oh My!

Swimming

Credit: iStock

The American Heart Association recommends that adults get at least 30 minutes of endurance exercise every day to keep your heart, lungs, and circulatory system healthy. A daily workout can help reduce your risk of developing diseases such as diabetes, heart disease and stroke. Endurance exercise is basically any activity that increases your breathing and heart rate for an extended period of time. Examples include:

  • brisk walking
  • jogging
  • dancing
  • biking
  • swimming
  • climbing stairs

During exercise, your blood vessels expand (dilate), increasing blood flow, and delivering more oxygen to your working muscles. Over time, exercise helps your blood vessels become more flexible. This flexibility allows the vessels to dilate more quickly to deliver blood and oxygen to your muscles. Long-term endurance exercise also increases the number of small blood vessels (capillaries) in your body. All of these things help carry more oxygen to your organs and remove waste more quickly. As a result, you can enjoy better athletic performance, such as being able to jog farther, run faster or swim longer distances.

A recent study in the American Journal of Physiology—Heart and Circulatory Physiology showed that endurance activity may help blood vessels grow by increasing the number of microvesicles in your blood. Microvesicles are small particles that are shed into your blood from all types of cells in your body. When volunteers in the study rode a stationary bicycle, they produced more microvesicles than when they were sitting and resting. The number increased even more when they pedaled faster. The researchers then added the volunteers’ microvesicles to endothelial cells—a type of cell that lines the blood vessels and is responsible for expanding and contracting them. They found that microvesicles caused endothelial cells to grow twice as fast. In other words, when you exercise, the number of microvesicles increases, which in turn helps your blood vessels grow.

Now you know why exercise builds a better circulatory system, so get moving!

Dao Ho, PhD

Dao H. Ho, PhD, is a biomedical research physiologist at Tripler Army Medical Center. The views expressed in this blog post are those of the author and do not reflect the official policy or position of the U.S. Department of the Army, U.S. Department of Defense or the U.S. government.

Are Cross-Country Skiers Premier Athletes?

 

Cross Country Skiing Couple

Credit: iStock

With winter upon us, it is a good reminder that cold weather is not an excuse for inactivity. Athletes from cold-weather climates, such as the Nordic countries, are not content to stay indoors during winter. In fact, cross-country skiers from these colder climates might be considered the premier human aerobic athletes.

Although some picture cross-country skiing as slowly shuffling along at a leisurely pace, the reality of competition is much different. For example, the winner of the 50 km (31 miles) freestyle at the 2014 Winter Olympics finished the race in less than one hour and 47 minutes. That’s longer than a marathon but finished in less time. And these races typically go uphill for 50 percent of the time!

Physiologically, skiing is interesting from many perspectives. The biomechanics of skiing are interesting because the arm and leg movements must be coordinated to efficiently move forward. The whole-body nature of skiing makes the physiology fascinating to study. Cross-country skiing puts large demands on the heart to deliver blood and oxygen to exercising muscle. This challenge is greater than for running or cycling (which engages only the legs) because both the arms and the legs need to work with skiing.

The amount of blood going to the arms versus the legs constantly changes, too. These changes are based on the hundreds of technique transitions needed to cross the varying terrain during a race. The great physical endurance required improves the ability of cross-country skiers’ muscles to use oxygen. These athletes have some of the highest levels of oxygen consumption (VO2max) on record. Legendary physiologist Bengt Saltin and other researchers have used the unique whole-body nature of cross-country skiing to study blood flow delivery. This approach has provided us great insight into the regulation of blood flow in both athletes and non-athletes.

Cross-country skiers demonstrate that cold weather is not an excuse to be sedentary, but rather an excuse to be great.

 

Ben Miller Benjamin Miller, PhD, is an associate professor in the department of Health and Exercise Science at Colorado State University. He co-directs the Translational Research in Aging and Chronic Disease (TRACD) Laboratory with Karyn Hamilton, PhD.

How Your Brain Decides to Keep Your New Year’s Resolutions (or Not)

 

New Year goals or resolutions

Credit: iStock

ispy-physiology-100th-post-imageThe start of a new year can feel like a fresh slate or an unwritten book. It’s a chance for many of us to resolve to do things better (eating, exercising) or to stop doing certain things altogether (smoking). But most people don’t succeed in sticking to their resolutions in the long term, and the reason might surprise you. It’s not always a question of lacking willpower or being lazy. Keeping resolutions makes your brain work hard, and that mental effort takes time and practice.

Researchers from the University of Minnesota found that your brain uses more than one decision-making system to build and regulate habit-forming and goal-directed behaviors. One system looks at the steps you take to make a decision. Another evaluates your actions and decides when you need to change a new behavior in order to receive a reward.

Here’s where the hard work comes in: The researchers explain that goal-directed behavior requires mental energy and planning. You have to plan ahead before making decisions to know how to reach your goal. Let’s say, for example, you’re trying to cut back on sweets and are invited to a party. If you want to enjoy a dessert at the party but don’t want to completely ignore your resolution, you’ll need to plan to eat less sugar during the rest of the day. Over time, as you keep making more goal-oriented decisions, the choices become more automatic.

Another study suggests that nerve cells stick together when you form a habit that you’ve enjoyed (such as eating dessert after dinner). The strong bond they create can be tough to break, and—like getting up early to go running or sticking to that diet—it isn’t always easy. This is especially the case when your emotions take over and you feel resentful or angry at the challenging changes you’re trying to make. Being mindful and keeping your emotions out of the decision-making process can help. Your brain, like your body, just needs time to adjust to your new routines.

Good luck and happy new year.

Erica Roth

2016’s Ten Most Read Posts

It’s been a physiology-full 2016 on the I Spy Physiology blog! From exercise to respiration to heart health and beyond, we’ve explored how the bodies of humans and other animals work, adapt and react. Today, we take a look back at our 10 most read posts of the year.

Concussions among football players was headline news in 2016. Against this backdrop, our most popular post of the year looked at how woodpeckers can bang their heads roughly 12,000 times a day at a greater force than the average football hit without sustaining a head injury. Posts about the amazing endurance of Iditarod sled dogs and a researcher’s excellent explanation of what physiology is and why it’s important round out the top three. Check out this year’s top 10:

If you’ve got a topic that you’d like us to cover in 2017, we’d love to hear from you! Share your thoughts in the comments or send us an email.

Stacy Brooks

Bring on Winter! (But Stay Safe and Healthy)

 

girl playing on a winter walk

Credit: iStock

Winter officially begins next week with the winter solstice—the day of the year with the fewest hours of sunlight—on Dec. 21. With the cold weather and shorter days, you might be tempted to curl up under a blanket until the spring thaw. Whether you plan to hibernate or get outside to enjoy the chill, we’ve got some good reads about how our physiology responds to the cold weather.

Check out these throwback posts featuring cold weather tips to help you stay safe and healthy during the coldest months:

Have fun, be safe and take note of how your body adapts to the season!

Stacy Brooks and Erica Roth

 

 

Exercise: It does a body—no, your brain—good!

Brain

Credit: iStock

It’s 7:30 a.m., I’m looking for my keys, grabbing my bag and herding everyone out of the door as we hurry off to school and work. Wait! One more trip back into the house for the forgotten homework assignment, a lunchbox and … it seems I have forgotten several things. Is it stress, lack of sleep or just the natural aging process? Regardless, it seems I need a memory-boosting workout.

Exercise is no longer just for affecting the size of your muscles, but also the size of your brain. As we age, the volume of our brain naturally decreases. However, in people at risk for Alzheimer’s disease, one of the numerous cognitive diseases under the dementia umbrella, there is a more marked decrease in brain volume. Being physically active has been shown to slow or even stop the decrease in brain volume in older people, even among those at risk for Alzheimer’s disease.

The Physical Activity Guidelines for Americans issued by the U.S. Department for Health and Human Services state that adults should get 150 minutes of moderate-intensity activity—such as walking, running, swimming and cycling—each week to promote and maintain health. These and other forms of moderate-intensity exercise have also been positively linked to maintenance of memory and learning as we age.

According to a recent study in the research journal Alzheimer’s and Dementia, reaching recommended physical activity goals has substantial effects on brain volume. Ninety-one adults ranging from ages 50 to 74 wore an accelerometer, a device which records and measures the wearer’s steps and speed of movement, for seven days. Subjects who performed physical activity for 150 minutes or more per week had temporal lobe sections that were 5–6 percent larger than their sedentary counterparts. The temporal lobe of the brain is associated with learning and memory. This sustained brain volume associated with physical activity was noted among people with a family history of Alzheimer’s disease, those who have the Alzheimer’s associated gene and those who were not at high risk.

The moral of the story? Get up and move. Your brain will remember to thank you.

 

Jessica Taylor updated 6-1-2016 Jessica C. Taylor, PhD, is an assistant professor of physiology in the College of Osteopathic Medicine at William Carey University in Hattiesburg, Miss.

Are You at Risk for Type 2 Diabetes?

Diabetes text with felt tip pen (Click for more)

During American Diabetes Month in November, you may notice more people are talking about diabetes, a disease that affects 29 million Americans. It’s a great time to learn more about diabetes and the ways that you can decrease or manage your risk of developing the disease.

Diabetes mellitus is a problem with how your body handles blood glucose (sugar). People who have type 2 diabetes aren’t able to use the hormone insulin properly to remove glucose from the bloodstream for use in the fat and muscle cells.  Ultimately, this causes people with type 2 diabetes to have higher than normal levels of glucose in their blood.

You may have heard that someone who is overweight and has a large, apple-shaped body is more likely to develop metabolic syndrome—a group of health conditions such as elevated blood pressure, blood sugar and cholesterol levels—which may increase the risk of developing diabetes.  However, there are a number of less well known risk factors for type 2 diabetes including:

Some research even links non-health-related factors such as job security to an increased diabetes risk. A recent study published in the Canadian Medical Association Journal  analyzed data from 19 different studies including almost 141,000 participants which suggested that job insecurity was associated with a modest increased risk of diabetes.  Job insecurity has also been associated with weight gain (a diabetes risk factor) and coronary artery disease (a complication of diabetes).

Recognizing risk factors for diabetes and dealing with them, if possible, is important for both children and adults. Consuming a healthy, nutrient-rich diet and staying physically active can help maintain weight, manage stress and avoid type 2 diabetes and its many related complications. To learn more about ways to prevent diabetes, visit the American Diabetes Association website.

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Barb Goodman, PhD, is a professor of physiology at the University of South Dakota.

The Young Qualities of Old Muscle

Senior Adults Taking Spin Class

Credit: iStock

Decline, decrease, deteriorate—all words associated with the aging process. Preventing “D” words is important to keep older people healthy. The loss of muscle is one of the most obvious age-related decreases we experience. Bulky muscles on a person that lifts a lot of weights or the sleek tone of a person that runs a lot of miles shows you that muscles of young people are amazing in their ability to change with the demands put on them. Scientists call this ability to change “plasticity.” When and why does muscle plasticity decline?

As individuals age, large muscle fibers that allow explosive types of movements, such as jumping or lifting a heavy weight, disappear more than small muscle fibers that allow slow, low-force movements such as grabbing a cup or adjusting posture. A recent Journal of Applied Physiology podcast discusses a research article that looked at small, medium and large muscle fibers from a group of subjects who were ages 87 to 90. At this age a substantial decline in strength is expected. However, the study showed that even though large muscle fibers are lost in old age, medium-sized muscle fibers become very strong for their size to compensate for that loss. The amount of force the medium-sized fibers could generate for their size was greater than muscle fibers from a group of young subjects and was similar to a world-class sprinting athlete. Therefore, the medium-sized fibers in the muscle of a very old group of subjects were plastic and adapted to the loss of bigger more explosive muscle fibers.

Future research is needed to determine if this plasticity is apparent in all old individuals or whether it was unique to this group that was still fairly active. Also, it is still unknown why some types of fibers keep this plasticity and others do not. Although older muscle does decline, decrease and deteriorate, plasticity appears to remain, which provides an interesting avenue to prevent the “D” words.

Ben MillerBenjamin Miller, PhD, is an associate professor in the department of Health and Exercise Science at Colorado State University. He co-directs the Translational Research in Aging and Chronic Disease (TRACD) Laboratory with Karyn Hamilton, PhD.

Looking for a New Physical Challenge? Try a Mountain Ultra-Marathon

Idyllic Alps Valley

The Aosta Valley in Italy where the Tor des Geants is held. Credit: iStock

Of all the extreme endurance races out there—such as the Ironman triathlon or 50- or 100-mile marathons—the Tor des Géants ultra-mountain marathon may be the most extreme. The course is 205 miles long on the rugged terrain of the Italian Alps with a cumulative elevation gain of 24,000 feet. Participants have 150 hours, little more than six days, to complete the course. These feats of ultra-endurance are fascinating for scientists because they showcase how the heart adapts when pushed to the limit. Previous studies have found that after 3- to 15-hour races like marathons and the Ironman triathlon, the heart doesn’t pump as well, a condition referred to as exercise-induced cardiac fatigue. A group of French researchers looked at what happened to the heart after running for over 100 hours in the Tor des Géants. They were surprised to find that unlike with marathons and triathlons, heart function improved after the ultra-mountain marathon race.

During a heartbeat, the heart fills with blood and then squeezes together to push out the blood. In situations in which the body constantly needs more oxygen, such as with exercise, the amount of blood filling the heart is one signal that tells the heart to keep beating harder. The more the heart fills, the stronger the heart contracts.

This study found that the runners’ hearts filled more during each heartbeat. The researchers think it’s because the amount of plasma, which is the liquid portion of blood, increased, raising the overall amount of blood in the body. But why it increased is not clear. Fluid intake could be one factor, says Michael Joyner, MD, an exercise physiologist not involved in the study, in a podcast. Runners in ultra-long races pay extra attention to staying hydrated and often maintain or gain weight from the extra fluids, he says. Stéphane Nottin, PhD, the lead investigator of the study, wonders if inflammation from the extreme physical stress or greater retention of sodium (the kidneys use sodium to absorb water) is also involved.

“Physiology has a long history of expedition-led investigations—whether it’s high altitude, desert—and this paper follows in that wonderful tradition,” Joyner says. Other current ongoing studies in this spirit include a Mount Everest climb to examine cognitive decline at low oxygen levels and a study on the heart of a swimmer swimming across the Pacific.

Maggie Kuo