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Over 30? Here’s What’s Happening To Your Metabolism

by Sportitude
1 Apr 2019

Remember mindlessly scoffing down a whole pack of Tim Tams in your teens and early 20s, with seemingly no affect to your waistline (or was that just us?).  

When you reach 30-something, the flat belly that comes easily for teenagers and young adults may have gone hiatus and left you wondering, why has my fast metabolism checked out?

But even if you haven’t been lucky enough to win the genetics lottery, you can make healthy lifestyle choices to love your bod deep into your 40s, 50s, 60s and so on with a little know-how about your metabolism and its role in your health.

What is metabolism?

Metabolism isn’t just an airy-fairy notion – it’s the biochemical processes that continuously occur in your body to sustain life.

Your metabolism is responsible for converting the food and drink you ingest into a usable source of energy to power literally everything you do – from cell repair, hormone regulation, blood circulation and digestion to thinking, breathing and singing your heart out on the drive home.

Most of us use the term ‘metabolism’ in the place of what’s more accurately known as ‘metabolic rate’ – a measurement of how much energy (kilojoules in food/drink) your body burns off over a period of time.  

What is your basal metabolic rate?

Your basal metabolic rate (BMR) is a measurement of how much energy your body requires to support basic, life-sustaining functions at rest.

The higher your BMR, the easier it is to keep a flat tum and ward off the muffin top without significant physical effort. In fact, the energy you use simply by being alive, contributes to a significantly high percentage (around 60 to 75%) of your overall energy consumption.

What factors influence your metabolism?

There are many factors that affect your metabolism including genetics, diet, sleep, body mass, gender and what we're going to focus on - age.

Hitting the big 3-0 isn’t a magic flip switch - your metabolism naturally and gradually slows as you get older, starting as early as your mid-20s.

Although these subtle changes creep up on us and remain virtually unnoticed until at least our 30s, the hormonal changes associated with age have a key impact.  

Age and hormonal shifts

In your 30s, your pituitary gland in your brain starts decreasing its production of human growth hormone (HGH) – it’s particularly important when we’re young and developing but also necessary for building and maintaining muscle mass.

After the age of 30, men’s testosterone levels gradually decline, but usually it’s not until reaching your 40s or 50s that you’ll experience noticeable symptoms including a decrease in muscle mass and increase in fat storage.

For women, reaching menopause in your 40s or 50s triggers one of the most significant hormonal shifts during your life - as estrogen levels decline, muscle mass decreases and muscle quality drops.

What does your muscle mass mean for your metabolism?

Muscle tissue requires about 3 times more energy to sustain than fat, so the more muscle you have the greater the kilojoules expended at rest and the less likely your body is to store fat in excess.

Sorry gals, but this is why men tend to have a faster metabolism than women – having naturally higher testosterone levels means an increased likelihood of developing and maintaining lean muscle mass.

But to keep it in perspective, when weighed up against your life-sustaining organs like brain, heart, liver and kidneys that are constantly working away to keep you alive, your muscles at rest only burn up a small portion of your daily kilojoules.

Quick fix metabolism-boosting schemes are short term

There's tons of seemingly 'miracle cures' to boost your metabolism; drink hot lemon water, keep your smoothies green and lean, turn down the air con to burn calories for temperature regulation, get your caffeine with a morning coffee fix or high quality dark chocolate (woohoo!), just to name a few. 

These little changes may help marginally in the short term but let’s look at the big picture.

The big picture: Strength train to maintain muscle

Seeing as muscle mass deteriorates with time and inactivity, strength training like dumbbell exercises and kettlebell training are particularly valuable in maintaining muscle mass as we age, even if there is no magic, one-size fits all way to dramatically boost metabolism.

You don’t have to be a super buff gym junkie to do these exercises either. Although heavy lifting and compound movements that activate multiple muscle groups like squats and deadlifts may add to faster muscle gains, more meditative exercises like yoga allow you to apply your own body weight as a strength training tool. As always, balance is key.

Should you forget about cardio?

Is it time to say cardio, smardio? Nope, this doesn’t mean you should skip out on fat-burning, heart-friendly cardio exercises like running or cycling.

They won’t result in building as much lean muscle mass compared to resistance training but performing exercise, particularly those that require higher effort acts as a temporary metabolism booster.

As these exercises (at lower intensity) won’t continue to speed up your metabolism all the way from your cool downs to cuddling up with an evening cuppa, it’s important to do them regularly and consider occasionally trading in your steady, long distance runs and their endurance benefits for HIIT workouts (high-intensity interval training).

HIIT – Your time-saving, metabolism-boosting buddy

High-intensity interval training involves short periods of exercise nearly or at the full capacity your body is capable of (e.g. sprinting at full-pelt) broken up by brief recovery periods (e.g. recovery jogs or walking) and can be applied to both your gym sessions and on your runs.

With these all-in, crazy sweaty workouts, even after you’ve stopped huffing and puffing your ‘oxygen debt’, or the amount of oxygen and energy required to fuel recovery and return your body into a normal, pre-workout state is considerably higher than it would be for longer, but less physically demanding workouts.

It’s called EPOC (excess post-exercise oxygen consumption) and there’s a lot of sciencey stuff behind it, but basically it means high intensity sessions prolong the metabolism-boosting or ‘afterburn’ effect of your workout, even long after you’ve unlaced your running shoes.

To sum it up

A more muscular, fitter body maintained with regular strength and cardio training has multiple benefits beyond increasing metabolism, including keeping your bones strong and heart healthy later in life – not to mention feeling empowered as you exercise your furry buddy without running out of breath, or lifting up your tiny tot with hulk-like strength without turning green.

But it is worth putting on your realistic thinking cap when considering your metabolism – because everybody is different and multiple factors are in play, including those you can control like eating lean muscle-building protein as part of a balanced diet, and those you can’t like genetics.

Your body is unique, but we can all benefit from staying active and committing to healthy lifestyle choices now and in the future – so sweat it up and have fun!