Pizza Party Perils: Does your metabolism have to slow down as you get older?

Part of getting older is not being able to eat all the crazy things you did as a kid. While teenagers may be able to eat an entire pizza in one sitting without showing any adverse effects, it is common knowledge that as we get older our metabolisms slow down and we put on weight more easily… But what if that wasn’t actually true?

To understand what I’m talking about you need to understand what the word metabolism actually means. Your body is a busy place. Even when you are sitting on the couch or laying in bed catching up on your favourite illustrated science blog, your body is hard at work doing a million different things. Blood is pumping though your veins, the muscles in your chest and diaphragm are flexing to pull air into your lungs, the synapses in your brain are firing at a rate that is hard you fully comprehend; and all of this requires energy. Your metabolism is just a measure of how effectively your body turns the food you eat into the energy you need to function.

A lot of things can impact your basal metabolic rate (the amount of energy your body uses to do all the basic functioning I just mentioned). Surprisingly, though, there isn’t as much variability as you might think. Many people claim to have a slow metabolism, but this is actual a pretty rare thing and is usually caused by an underlying medical condition like hypothyroidism or Cushing’s Disease. In truth, the big things that impact your metabolism are your sex and body composition.

Generally speaking men have less body fat than women and more of their weight is comprised of muscle mass. Even at rest, muscle burns more calories than fat so men tend to require more energy just to maintain a basic level of function. While you may not be able to control your sex, you have a measure more control over your body composition (within reason). People who lift weights can increase the proportion of their body weight that is muscle and thereby burn more calories. That is what is meant by body composition. Your age can work to slow down your metabolism, but only if you allow your muscle mass to decrease. Go to any master’s (over 40) track and field meet and you will find a whole suite of people who maintain speedy metabolisms simply by continuing to exercise and not letting their muscles deteriorate.

Particularly intense exercise has the added bonus of keeping your metabolism elevated for a period of time after you are done your workout. Known as “excess post-exercise oxygen consumption” (EPOC), the phenomenon is caused by the recovery processes taking place after a hard day at the gym or the track. A recent swath of articles in the fitness world with a surprising amount of science behind them argue that as you increase the intensity of a workout, you can get the same physical benefits of working out at an easier level for much much longer. Some have even suggested that if you run hard enough, 5 minutes a day can give you all the benefits of running slowly for an hour or more.

But If exercise isn’t your thing and you want to boost your metabolism anyway, there are options. One of the best is nicotine, which speeds up your heart rate and forces your body to burn more calories. The Mayo clinic suggests that smoking 20 cigarettes per day is roughly equivalent to putting on 90 lbs in terms of increase to your metabolic rate. (Contrary to popular thought, fatter people actually have faster metabolisms than skinnier people with the same activity level because it takes more energy to move blood around their bodies and they are likely to have more muscle mass.) Obviously nicotine has its drawbacks if you enjoy being alive and hope to continue in an animated state for a long period of time, but if all you’re going for is metabolic speed, it will help.

But even with the help of devastatingly harmful drugs and all the exercise we can handle, humans are wimps in terms of metabolic flexibility. Many animals can put us to shame. Bears in particular are masters of metabolism. Research has suggested that during their winter rest period (not technically hibernation) bears can reduce their metabolic rates by 75%. The net effect is reducing their body temperature by up to 6 degrees! In humans, that is grounds for hospitalization, but the bears manage it just fine. They don’t fully warm up again until up to three weeks after leaving their dens.

So in the end, you metabolism may not be an entirely changeable thing. But next time someone tries you give you spin about your metabolism slowing down with age, set them straight and tell them to hit the gym.

Opah! Warm blooded fish derails conventional science

The study of biology can turn even the most open-minded person into a bit of a snob. As you learn about the infinite complexity of the living world and begin to understand how body systems have evolved to cope with a never-ending struggle for survival it is easy to fall into the trap of thinking one way of doing things is better than another. This can lead to thinking of some species as “primitive” compared to humans and over the course of history this idea has been used to justify some pretty heartless treatment of animals from testing cosmetics to making bears ride unicycles.

A great example of how biology tends to split up animals is the study of thermoregulation, or how animals control their body heat. Although there are animals that exists across a spectrum of temperature controlling abilities we tend to lump all the life on our planet into one of two buckets: warm blooded or cold blooded. Cold blooded animals (also called ectotherms) use forces outside their body (mainly the sun) to regulate their metabolisms. If they need to speed things up, they go lay in the sun for a while. When they begin to overheat, they go lay in the shade. Warm blooded animals, by contrast, can use internal forces like muscle contraction and widening or narrowing blood vessels to keep things in check, regardless of whether or not the sun is shining.

Generally speaking, the warm blooded camp includes mammals and birds  and team cold-blood includes everything else. The upshot is that since humans are warm blooded mammals and we are the ones who publish the bulk of the scientific papers on this planet, cold bloodedness tends to get spun as being “less advanced.” Fortunately, science builds its understanding of things over time and recent research is beginning to demonstrate that things aren’t quite as neat and tidy as some of us wish they were.

Fish, for example, are the quintessential primitive, cold blooded animals. When they leave the warm and sunny waters near the surface for a deep dive, they become sluggish as their bodies cool down… But not all fish. On May 15, 2015 researchers reported in the journal Science that a fish called the opah seems to defy this description.

The opah is a cool animal to begin with. It is roughly circular in shape, with powerful looking fins. It is red with white polka dots, and can grow to 90 kg (200 lbs) in weight and be about the size of a car tire. But it turns out that the coolest thing about the opah is that it isn’t really cool at all. The opah is the first fully warm blooded fish ever discovered. Through flapping its fins and changing the way warm and cool blood exchange heat in its gills, the opah can keep its body temperature 4 to 5 degrees C (7 to 9 F) above the temperature of the surrounding water. This gives it an advantage in hunting cold blooded fish at depth and means it never has to move to the surface to warm up.

Other fish like tuna and some sharks have been found to be able to heat up specific parts of their bodies when gearing up to hunt, but to avoid damaging their organs they eventually need to move to warm water.

The process used by the opah is actually pretty similar to how humans stay warm when its cold outside. When our body gets cold it sends a message to the hypothalamus in our brains, which acts as our internal thermostat. The brain constricts blood vessels near the skin and in the extremities to reduce heat loss (this is why your ears, fingers and toes get so cold so fast). The hypothalamus can also use muscle contractions and hormonal reactions to produce heat in the body.

Interestingly, the opah isn’t the only animal to throw a wrench in the gears of cold blooded classification. Dinosaurs, in case you didn’t already think they were awesome, defy conventional categorization and have forced scientists to create a third label “mesotherms” to explain how they regulated heat. The trouble with dinosaurs is that there aren’t any around to study, but by looking at growth rates compared to how much energy is burned in living animals, scientists have been able to piece together how  dinosaurs bodies might have worked. They lie in between cold bloodedness and warm bloodedness… More akin to tuna than lizards.

So once again the human urge to lump things into groups is thwarted by the complexity of nature. Just another reason why the guys who wrote the biology texts in the 19^th century should have been more afraid of sharks and dinosaurs.

The Trouble with Chairs: How Doing Nothing is Doing You Harm

Living a healthy lifestyle is as difficult as it is important. We saw in our discussion of Epigenetics that the bad decisions we make about our health today can have consequences for not only ourselves, but generations of our offspring. Eating right and exercising regularly are the two crucial things that everyone knows to do to protect their health; however, recent research is beginning to realize that there may be a third factor that is just as important: sitting.

A paper published by the American College of Sports Medicine suggests that if you spend too much time with your feet up, your lifespan may be headed down (Katzmarzyk et al., 2008). The study included over 17,000 Canadians between the ages of 18 and 90 and compared overall mortality with a number of lifestyle factors. The researchers determined that even after controlling for obvious factors like age, diet, and exercise, time spent sitting was correlated with a significantly increased risk of death from any cause.

That is a complicated thought so let’s take a second to think about it. When researchers “control” for something they are trying to rule it out as a cause of some effect. In this case when the researchers control for exercise, for example, they are basically comparing their findings across groups of people who exercise similar amounts. Ditto for diet and age. Even after doing this the effects they found were significant. That means that even if you go for an hour long run after sitting behind a desk at work for 8 hours, you are still at an elevated risk of death compared with a mail carrier, for example.

Other research has linked excess sitting to colon cancer, breast cancer, heart disease, and chronic chest pain. To understate things dramatically: this is bad news. We live in a world that is designed to promote sitting. Buses and trains are basically mobile rooms full of chairs. We sit to eat, we sit to work, we sit to read about how bad sitting is for us (caught you). So what can we do?

Doctors have begun taking this research to heart and have offered several recommendations. First, if you have a job that requires you to sit all day, use your time away from work to be more active. Stand while you watch TV, stand while you eat dinner, go for a walk before breakfast. Much of the problem comes from the fact that when we sit, our muscles don’t contract. The minor contractions that go along with shifting from one foot to the other or moving things around with our arms help our bodies to metabolize and remove fats and sugars. When we sit, those processes shut down and we store harmful waste products in our bodies. The science has even specifically shown that sitting all day increases fat storage around the middle of your body… and beach season isn’t far off.

If you’re the especially wacky type, Amazon offers a plethora of stand-up work station options. You can buy the exercise bike with the laptop tray. There are plenty of desks with the work platform at chest height. You can even buy a treadmill complete with a desk, file sorter, and pen organizer. In his book  Drop Dead Healthy: One Man’s Humble Quest for Bodily Perfection, A.J. Jacobs brags that he walked over 1000 miles (1,600 km) while doing his writing.

Clearly not all of us are cut out for that sort of dramatic undertaking, but we can do some of the little things that the experts recommend. Take a 5 or 10 minute break once an hour to get up and walk around your office. Instead of sitting in a boardroom for a meeting, invite your coworkers to go for a walk while you talk about your next project. An evening stroll after dinner won’t only prolong your life, it might make you enjoy it a little more too.

Usually when bad news makes its way down the scientific grapevine we need to make big changes to our lives if we want to keep enjoying them. Working out is tough and there are days when the thought of going to the gym is tantamount to cruel and unusual punishment. Walking by a pizzeria, smelling the delicious aromas and not going in for a slice is an act of willpower worthy of a medal. By comparison, a little extra standing isn’t such a big deal. Besides, if anyone tries to judge you for it, you are already in position to look down your nose at them. And, in case you were wondering, yes researching this article scared me into action myself. I now spend 6 of my 8 working hours a day standing at this wonderful monstrosity trying to avoid an early grave:

If a lazy blogger can do this, what's your excuse?

Other References:
http://revdesportiva.pt/files/form_cont/Sitting_Time_and_Mortality_from_All_Causes.pdf