Wednesday, August 29, 2012

Burning for you

Yesterday, we discovered that diet, more so than physical activity, is responsible for gaining and losing weight.  Not that I or any of us ever think about calories... but today’s follow-up cites a fun and well-written insight into foods and calories from the Scientific American web site.

The main newsflash of this article is that the number of calories we absorb from a particular food product varies, for a number of reasons. 

Why calorie counts are only guidelines

You and I, for example, will absorb calories from a given type of food (such as a tomato or a lamb chop) differently, depending on the amount of time we cooked the food, the microbes living in our respective guts, and even our ancestries (apparently, Russian intestines are about five feet longer than those of Italians – I always knew that someone named Palminteri just shouldn’t be eating beets!).

Cooking and pounding meat makes it easier to digest and absorb the calories from it.  Same for veggies.  Processing our food in the kitchen does some of the work that our teeth, stomachs, and intestines would otherwise have to do.  To put it bluntly, as the article's author Rob Dunn, a biologist at North Carolina State University, states, “If you want more calories, cook, pound and otherwise predigest your food.”

This holds for industrial processing: eating white bread and cheese wiz asks little of our teeth or our digestive system to give us calories.  In fact, eating an equal portion of whole wheat bread and cheddar cheese actually provides you with 10% fewer calories because digesting the whole foods requires some energy.

We share nutrients from food with trillions of microbes, which live in our guts and help to break down many compounds our own bodies can’t.  The calories lost through this sharing process, as well as those used by our immune systems to fight off disease from food contaminants, are not considered in the calories attributed to specific foods or published on food labels.

Cooking counts for calories

Nowadays, many of us are trying to reduce the number of calories we consume, yet maximizing caloric intake through food processing (mainly cooking) may have played a huge role in our evolution.  In the age before fire, our paleo ancestors ate their food raw and would have craved excess calories.

According to Harvard biologist Richard Wrangham and others, cooking food may have allowed early humans to extract more energy from their food.  By spending less time chewing tough raw food, they would have had more time to develop agriculture, tools, and social networks (which back then meant actual talking).  The easier digestion and better calorie absorption may have also contributed to the development 1.8 million years ago of larger brains –  which consume substantial amounts of energy – and relatively smaller guts, jaws, and teeth.
   
With a few exceptions, we as a species have thrived in large part because of our combined preference for cooked food and our unique ability to make it on demand.**

**However, raw and less-cooked foods do tend to have more nutrients and minerals, so, like exercise, they are good for us beyond their impact on our weight.  And as we learned yesterday, one third of Americans are considered obese: we humans now consume too many calories, and too many of those calories are of low quality.

For more information on these cooking studies, you might want to consult the Harvard University researchersRachel Carmody and her collaborators studied the mice that preferred and grew heavier on cooked and pounded meat and sweet potatoes.  Richard Wrangham’s new book makes the case that the ability to harness fire and cook food allowed our brains to grow and the digestive tract to shrink.  

Tuesday, August 28, 2012

Overweight? Overeating– not our modern, sedentary lifestyle– is the likely culprit

You hear the irony on the news – we see famine in parts of our planet yet a global obesity epidemic has worsened over the past 20 years.  It’s particularly obvious in the U.S.: more than 1/3 of U.S. adults (35.7%) and approximately 17% (or 12.5 million) of children between 2—19 years old are obese.

What does it mean to be “obese”?  The Center for Disease Control (CDC) defines an obese person as one with a body mass index (BMI) of 30 or higher, while an overweight person has a BMI of 25 or higher.  Go ahead and check your BMI with an online table or calculator and report back.

More than just an image issue

The situation is urgent for many people:  as your weight increases to reach the levels referred to as "overweight" and "obese," you face higher risks for a number of real and problematic health issues:
  • Coronary heart disease
  • Type 2 diabetes
  • Hypertension (high blood pressure)>
  • High cholesterol / high levels of triglycerides
  • Stroke
  • Cancers (endometrial, breast, and colon)
  • Liver and gallbladder disease
  • Sleep apnea and respiratory problems
  • Osteoarthritis (a degeneration of joint tissue).


These conditions – and, thus, overweight and obesity – are linked to larger-scale suffering as well, not to mention increased medical costs ($1,400 higher in 2008 than a normal weight person) and higher indirect costs (i.e. income lost from decreased productivity or absenteeism from work).   Studies have found that obesity increases lifetime medical care costs for these diseases by 50% above a healthy-weight baseline.  So maintaining a healthy weight is good for your wallet, as well as your well-being. 

Environmental and genetic factors contribute to body type and condition, but our behavior (aka diet and exercise) is the key aspect of our lives that we can change to prevent and help treat weight-related illness.  But which behaviors are most likely to prevent weight gain?

Energy savers 

According to the CDC and the World Health Organization, overweight and obesity result from eating too many calories and not getting enough physical activity. As more of us remain seated at our computers or on motorized transportation, we do get much less physical activity than our ancestors did.

However, it seems that overeating, more than our lack of activity, is to blame for gaining weight, according to recent research led by Herman Pontzer of Hunter College. 

Pontzer and his team measured the energy (calories) burned by members of the Hadza people, a group of traditional hunter-gatherers in Tanzania that lead physically active lives.  The Hadza walk miles each day: women forage for tubers, berries, and wild plants while carrying water or babies on their backs, and men collect honey and hunt with bows & arrows. 

Hadazbe returning from hunt
Hadza men returning from a hunt. Photo: Andreas Lederer

The Hadza don’t suffer from Western diet-related diseases such as heart disease or diabetes, a testament to their active lifestyle.  However, despite their greater physical activity, the number of calories that the Hadza burned per day was no different from that of typical adults in Europe and the U.S.  

How could this be?  I wondered this too.

Apparently, even for very active people, the body’s continual internal maintenance of its temperature, cells and systems – not our daily run, swim, or Zumba class – accounts for most of the calories burned in a given day.  

Pontzer and his colleagues think that energy (calories again) used by the Hadza for normal at-rest functioning may be less than that of less active people, so their total energy expenditure was similar to those among modern populations.  In other words, our bodies may be able to adjust our energy needs to our daily routines to keep total energy expenditure stable. 

I’m a huge fan of exercise, and I believe it is essential to staying fit, both physically and mentally (yes, I go crazy after a couple of days if I cannot exercise, though this may stem from the equally great joy I get from eating!).  But despite the numerous health benefits of working out, there seems to be little correlation between a person’s level of physical activity and how fat he or she becomes.  Or, in Pontzer’s words, “We’re getting fat because we eat too much, not because we’re sedentary.

Monday, August 20, 2012

Gold medalists of the natural world

Who’s fitter than an Olympic athlete?  In the spirit of the 2012 Olympic games, the International Union for Conservation of Nature (IUCN), nominated its “gold medalists of the natural world”.  The Guardian newspaper in the UK publicized this article, adding some excellent photos of the winners. 

Here are the winners of a few of the athletic events highlighted by the IUCN:
Cheetah on the move


Sprinting – The cheetah wins the sprint competition, running at speeds of 112 km/hour (70 mph) over short distances.  Sarah, a cheetah at the Cincinnati Zoo, ran the 100-meter dash in 6.13 seconds, almost 3 seconds faster than Usain Bolt's world record time of 9.58 seconds (also in 2009, a good year for speed!). 
Photo: http://www.wallpapersfreebackgrounds.com//running-cheetah.html


Arctic tern - taking a break?
 
Marathon– Arctic terns are the distance champions.  Each year for up to 30 years, these birds navigate a round-trip migration of over 70,000 km between the Arctic, where they breed, and the Antarctic oceans, the longest-distance migration of any bird. 
Photo: Tom Curtis, http://www.freedigitalphotos.net



Common froghopper

High jump – The Common Froghopper, a bug common across Great Britain, captures the gold in the high jump competition.  This super bug can jump 115 times its own height - equivalent to you or me jumping 200m!
Photo: copyright-free-pictures.org.uk





Marine iguanas sunning with a sea lion


Triathlon – The Galapagos marine iguana is the world’s only lizard that runs on land and swims (to depths of 20m) beneath the ocean.  The ability to move well in both arenas helps the iguana live on isolated islands that may have limited food available.   They have yet to master the art of cycling, though. Photo: putneymark via Flickr


Young gibbon hanging on


Artistic gymnastics – The winning gymnasts here were the agile gibbons.  Gibbons gracefully swing, hand-over-hand (a movement called brachiation), through the trees, and they can reach a branch up to 15 m (50 feet) away in a single swing.  Like the tumbling runs of the Olympic gymnasts, gibbons can twist and turn while they swing.   This one may be considering a front flip?  
Photo: Glen Bowman, http://animalphotos.info




Wilson's bird of paradise

Rhythmic gymnastics – Males of many of the 40 bird of paradise species dance to attract females, and their sometimes elaborate costumes (feathers) and routines take getting the girl to a higher level.   Some dance alone, while others assemble at a single spot in gatherings called “leks”, where they to compete for passing females by showing off their feathers and dancing skills (team medal, perhaps?).  Photo: Doug Hanson






Peregrine falcon flying
DivingPeregrine Falcons can reach up to 200mph (320km/h) when swooping through the sky in pursuit of prey, usually other birds. The fastest ever dive recorded was 242mph (390km/h).  Peregrines have special nostrils and eyelids that allow them to breathe and see during these super-fast dives.  Their main dive style involves folding back their wings and tail, tucking in their feet, and swooping downward, striking the passing bird with a clenched foot.  The impact stuns or kills the prey, and the falcon then turns to catch it in mid-air.   Photo: Kevin Cole

Oxpecker riding an impala

Equestrian – This medal is shared by the yellow-billed oxpecker and red-billed oxpecker, two bird species that ride on the backs of African grazing mammals, including cattle, eating ticks and other parasites living on their host.  Even their courtship takes places on top of their hosts.
Photo: PaulBanton72, http://www.stockfreeimages.com


Rhinoceros beetle
Weightlifting – The rhinoceros beetle can carry loads of more than 30 times its own weight, making it one of the world’s strongest animals (though, apparently, some dung beetles may be equally strong).  In comparison, Hossein Rezazadeh’s official world record for the heaviest individual weight lifted by a human in an Olympic competition is 263.5kg (580.9 pounds), approximately 1½ times his own bodyweight and equivalent to lifting four average-sized people.  Photo:  ThinkQuest.org


Of course fitness in the animal world varies by species – running fast is important for cheetahs but not for gibbons, falcons, or oxpeckers -- each species relies on its unique combination of characteristics to survive and reproduce.  In fact, you can click here for a whole page of natural born record holders. 

Fitness introduction

Recognizing that fitness is important for a long and healthy life for all species…

We all want to be fit and healthy, and some of us work hard (harder each year, right?) to stay in shape.  To stay fit, we try to eat right and exercise.  In addition, we try to maintain good bonds with family and friends while also striking out on our own, find a great home and a suitable life partner, and aim for some sort of balance between home and work activities.

The term “fitness” has a special meaning when applied to other species: fitness measures reproductive success.  Sounds good, right?  Specifically, it measures how successful an animal or biological population has been at passing on its genes to future generations.  Improving one’s genetic contribution to the next generation entails living long enough to reproduce, reproducing, and then ensuring your offspring also reach maturity so that they can reproduce.   It’s a bit like seeking immortality, through improved survival, higher mating success, and more mature (i.e. reproducing) offspring.


How do different species maintain their fitness?

They eat right, exercise, maintain family bonds, strike out on their own, find good homes in good neighborhoods, find a suitable mate, raise kids, and hope they succeed in life.  Sound familiar?  We share most of our DNA (the hereditary material in humans and almost all other organisms) with many other species (over 98% in the case of chimpanzees and gorillas), so the similarity makes sense.

Gharial (crocodile family)
Geneticists link fitness to alleles (alternative forms of genes located at a specific position on a specific chromosome), which might vary among individuals in a population.  

For example, while everyone in an early human population had eyes and a nose, some noses were larger, some were smaller, some were pointy, etc.  If having a larger nose somehow led to the owners contributing more of their genes (with the large-nose allele built in) than did the folks with smaller noses, then eventually, after many generations, larger-nosed people would be more common.  

What would increase their chances of contributing more genes?  Well, if having a larger nose allowed them to smell a scarce resource that let them survive longer, or it was seen as attractive and allowed them to mate with more members of the opposite sex, or it led women to eat healthier food and thus produce more healthy babies, or smelled danger from a greater distance so they could better protect their children, then it would be more likely to eventually produce more mature children.

Slightly more technical: Fitness is usually referred to for a genetic trait or a population, rather than just a single individual.  Have a large nose might generally improve survival among a group of people, but any given individual large-nosed person might unexpectedly die in an accident before having children.  Thus, the overall benefits of having a large nose affects the ability of an average member of a biological population to survive and produce mature, reproductive offspring. 

You can find many excellent blogs on diet, exercise, and maintaining your own fitness on the web.  I’ve included just a few of them here, as well as several excellent blogs dedicated to fun facts about other species and the wonders of the natural world.

As an athlete and a conservation biologist, I hope to combine the two to focus on fitness, for both humans and non-humans.  It is the essence of life and the basis of most animal and human behavior.