What is metabolism and can you boost it?

This article appeared on the SumoSalad blog in 2029. Click here for the original.

So, what is metabolism anyway? It’s a word that’s so often mentioned, but the meaning is kind of elusive. Is it a genetic thing you’re born with? Does it make you lose or gain weight? Can you really fire it up with a spicy curry or stacks of coffee? We quizzed nutritionist Ashleigh James to find out the metabolism basics and the best ways to keep it humming.

What is metabolism?

It’s time to put your lab coat on because this is where the science comes in. “Metabolism is the sum total of all the chemical reactions that happen in the body in the breaking down of carbohydrates, lipids (fats) and proteins, and the conversion of them into energy,” explains Ashleigh. “We often don’t think about how the food we eat powers all the activities of daily life. But that’s really what we are talking about when we talk about metabolism – it’s our body breaking down foods (and other things) to provide energy for life.”

The biggest component of your metabolism is your Basal Metabolic Rate (BMR). “This is the energy your body burns just to maintain functioning at rest. This includes maintaining our heart rate and blood pressure, body temperature, digestive functions and breathing,” says Ashleigh. This accounts for 60-80% of the energy used each day. “Other influences include how much physical activity you do and the ‘thermic effect’ of the food you eat – the energy you use to digest and absorb your food.”

Can you fire up your metabolism?

There are a few things that get your metabolism humming. “The major one is muscle mass. Muscle requires more energy to function than fat, so the more muscle you have, the more energy your body needs just to exist,” Ashleigh explains. “You can increase your muscle mass through exercise such as weight training, which will in turn have an impact on your BMR.” Essentially, cardio gives you a good short term calorie burn, but strength training allows you to burn more while you’re sitting watching Netflix. Yes please.

Age is also a factor – your metabolic rate generally slows down as you get older. And by older, we mean as young as 30. Oh. “This is partly because of a loss of muscle tissue, but also because of hormonal and neurological changes,” says Ashleigh. “After the age of 30, your BMR starts to slowly decline, whereas children and teenagers have a high metabolism to coincide with growth periods.” Makes sense, right?

The other factor is your body size. It makes sense that a 6-foot-tall man burns more energy at rest than a 5-foot-tall woman. “People with bigger bodies tend to have a larger BMR because they have larger internal organs, higher fluid and blood volumes, and more skin surface area. Therefore, the body works harder to maintain body temperature and other functions,” says Ashleigh. “Men also tend to be bigger than women so their BMR is usually higher. Genetics, hormonal imbalances and environmental factors like outside temperature all also impact BMR.”

What won’t make a huge difference is that spicy curry. You might have heard about foods like chilli firing up your metabolism, but they’re unlikely to make a meaningful difference every day. Same goes for so-called ‘metabolism boosting’ supplements. “There is little scientific evidence to show that any foods or supplements can boost your metabolism,” Ashleigh points out. “Some foods like caffeine may have minor short term boosting effects, but products that claim to speed up your metabolism are often more hype than help, and some may cause undesirable or even dangerous side effects like increased heart rate. The focus should be on developing healthy dietary and lifestyle changes.” In short: nourishing and balanced meals are your best bet.

Sadly, snacking doesn’t speed up your metabolism, either. “I don’t advocate for many small meals a day – there is no scientific evidence to suggest this increases our metabolism,” Ashleigh points out. “If you don’t wait long enough between eating times, you risk taxing your digestive system. Your body doesn’t get enough time to break down the food between meals, which means you will have high-circulating glucose in the blood, which is linked to inflammation.” Shame.

Does fasting boost your metabolism?

This Mexican Breakfast Bowl from SumoSalad is a delicious, balanced breakfast

One thing the jury is still out on is fasting. We know that a balanced breakfast can be an important part of a healthy diet. It’s meant to kick-start the metabolism and get you into gear for the day. However, there is also growing evidence that intermittent fasting can have beneficial fat-burning effects. In fact, a 2019 study in the journal Scientific Reports found that fasting may help boost human metabolic activity. So, what’s the deal?

“The body uses a lot of energy stores for growth and repair through the night and eating a balanced breakfast helps up our energy, as well as replenish protein and calcium stores used throughout the night,” explains Ashleigh. “I am an advocate for a healthy breakfast, but on the flip side of this is the intermittent fasting movement, which suggests we should skip breakfast to widen the period of fasting. This notion does have scientific backing, and there is evidence that points to intermittent fasting being beneficial for blood glucose and insulin sensitivity. So it’s really what works for you; if you can skip breakfast and not go overboard later in the day, then go for it. But if you are someone who is hungry in the morning, it’s probably a good idea to have a balanced meal.”

Crash dieting will mess with your metabolism

There’s one thing experts do agree on: crash dieting will wreak havoc on your metabolism. Not only does it slow it down, it reduces that metabolism-boosting muscle mass. “Extreme weight loss in a short amount of time will cause your metabolism to slow, which in turn can lead to more weight gain in the future,” says Ashleigh. “This is because once you stop dieting, you start eating normally again but your metabolism will still be functioning at the lower rate. Limiting and restricting calories also deprives your body of critical nutrients, and impacts on your lean muscle mass.”

As well as messing with your metabolism, extreme dieting stresses your immune system, can lead to exhaustion and dehydration, messes with your hormones and can even harm your heart if you keep it up long term. Yeah, no thanks. Ashleigh’s advice: “Take a look at your overall eating and exercise habits and make adjustments slowly that are maintainable long term.” Essentially, a healthy and balanced diet is the best way to make friends with your metabolism for life.

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