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.