Weight loss and metabolism: What you need to know

As you age, your body goes through a lot of changes, whether it's going grey or hair in all the wrong places. There's a stack of reasons behind this, from the food you're eating to the amount of exercise you're doing, to your hormones and genetics.

But one of the biggest factors that can influence your weight is your metabolism.

Your body has a unique metabolic rate that determines how quickly it burns energy. The interesting thing is that your metabolic rate isn't static, and can change as you progress through life. If you've wondered why, when you were younger, you could eat whatever you wanted without putting on body weight, but today, the idea of a greasy burger sees an extra kilo or two on the scales, that's your metabolism changing alongside you.

It's safe to say there's a lot to unpack when it comes to how your metabolism might impact your ability to lose weight. Let's dive into how your metabolism works, the role your metabolism plays in achieving a healthy weight, and some common FAQs about whether you can turn that slow metabolism into a fast metabolism.

What is metabolism?

Let's start with the basics.

Your metabolism is a bodily, chemical process responsible for turning food into energy [1]. It can be helpful to think of your metabolism as how efficiently your body burns through calories. For some, your metabolic rate might be very fast (which means you burn through the foods and drinks you consume quickly).

On the flip side, you might have a slow metabolism that takes a longer time to process food for energy (meaning you burn fewer calories each day). For example, if you've got a slow fat metabolism, it could take your body hours longer to burn calories than somebody else.

Your body needs vitamins, minerals, fats, carbs, and protein to survive. So, your metabolism is an essential process that converts the foods you consume into energy that your body can use to function.

What is your basal metabolic rate?

The rate at which your body processes energy is known as your basal metabolic rate (also called your resting metabolic rate) [2]. As the name suggests, this figure indicates the minimum number of calories or kilojoules your body needs to survive. Usually, it takes into account basic bodily functions, such as breathing, circulation, digestion, and cell production.

So, how can you figure out your BMR? The most widely accepted formula is known as the Harris-Benedict Equation, which uses your height, weight, age, and gender to come up with your BMR [3].

There are stacks of interactive online tools that can help you figure out this rate, or you can use the formula below:

• BMR = 66 (13.7 x weight in kg) + (5 x height in cm) - (6.8 x age in years)

Another one you can use is the Mifflin-St. Jeor calculation, which is:

• BMR = (10 × weight kg) + (6.25 × height cm) – (5 × age y) + 5

By figuring out your basal metabolic rate (BMR), you can get a ballpark figure of how much energy you need to be consuming each day to keep your body functioning.

What role does a healthy metabolism play in weight loss?

As you can probably tell, your metabolism plays a big role in your ability to lose weight. But it's also important to note that it's not the only factor influencing your weight-loss journey and your ability to navigate weight gain.

First up, let's dive into exactly how your metabolism works [2]. There are 2 core components to your metabolism.

• Catabolism – A process where your body breaks down the food you consume into simpler forms that your body can use for energy
• Anabolism – Another type of process where your body uses this energy to grow and repair different cells throughout your body

The other important thing to know about your metabolism is this: if you consume more energy (a.k.a. food) than you need, it'll typically be stored in your body as fat.

With that in mind, your metabolism plays an important role in regulating your body fat levels and influencing your capacity for weight gain. But the equation is much more complicated and nuanced than simply calculating how many calories we consume versus the rate our bodies burn calories daily. It's the same principle that consuming fewer calories alone won't lead to instant weight loss.

First up, research shows that the human body is hard-wired to slow your BMR if it isn't consuming enough calories or energy [1]. It's a biological response to prevent starvation, which means that simply eating fewer calories won't instantly equate to losing weight. Yes, getting a negative energy balance and preventing too much excess energy matters, but that's why if you want to achieve and maintain weight loss through your eating habits, it's a long process.

Plus, your genetics have been shown to play a big role in whether your body is predisposed to weight gain or weight loss [4]. Your genetics have the power to influence your appetite, your food cravings and even your ability to feel full between meals. For some people, their genetics account for up to 80 per cent of their predisposition to become overweight [4].

With that in mind, it's important to remember that your metabolic processes and metabolic rate aren't the only things determining your weight management.

Can you get a fast metabolism for successful weight loss?

Unfortunately, most of the research points to no.

Over the years, there have been stacks of foods, drinks, and fancy diet products claimed to increase your metabolism (from chilli peppers to coffee, and even radical crash diets). However, there's little scientific evidence to back up these claims that you can alter your metabolism to hit your weight loss goals.

That's because your metabolism is influenced by factors that are hard to change or influence, such as your gender, age, and genetics.

Research has shown that exercise increases lean muscle mass (which can help your body burn more calories). While there's little evidence to suggest that an increase in exercise changes your metabolic rate, it's clear that increasing your daily movement can help you burn more energy.

Some people explore eating patterns like calorie cycling in an effort to “trick” their metabolism. This approach, often referred to as metabolic confusion, involves alternating between high- and low-calorie days to help prevent weight loss plateaus and keep the body guessing. Again, the scientific evidence is mixed on whether this actually works.

While the science remains mixed, some people turn to so-called metabolism-boosting foods like green tea, spicy peppers, and protein-rich foods. While they may have a small thermogenic effect, they aren’t magic bullets that'll lead to weight loss and your desired body size.

Why does your metabolism matter for a healthy weight?

Your metabolism plays an important role in your body's composition and your ability to lose weight [5]. Your basal metabolic rate is largely responsible for how much energy your body needs.

If you're looking to lose weight or prevent weight gain, knowing how much energy you should be consuming daily can help you hit your weight goals.

Supporting your metabolism isn’t just about burning calories. It’s also a key part of your overall metabolic health, which includes blood sugar control, cholesterol levels, and more. A balanced approach to nutrition and movement can help keep these systems in check.

What other risk factors can impact your metabolism?

Wherever you are in life, there is a range of metabolic disorders that can influence your capacity to lose excess weight [7].  If you're trying not to gain weight but you're putting in the work, including getting enough physical activity, eating a healthy diet, and improving your overall health, there could be several metabolism-impacting conditions in play. These include:

Thyroid disorders

Your thyroid contains glands that are responsible for regulating your hormone levels. An underactive thyroid occurs when your body isn't releasing enough hormones to support a healthy metabolism.

An overactive thyroid, on the other hand, means your body is overproducing these hormones (which can speed up your metabolism).

Fructose intolerance

This genetic disorder means your body isn't able to process the type of sugar found in fruits and some vegetables.

Galactosaemia

This is another genetic disorder that can impact your metabolism. It occurs when your body isn't able to convert carbohydrates into glucose effectively.

What you need to know about weight management to lose weight

As you progress through life, changes in your weight are perfectly normal. But it's also important to know your options and make informed choices about how to hit and maintain your set point weight if it does happen. Likewise, you want to protect your lean muscle to maintain the figure you want.

The key is to look for sustainable, holistic weight management strategies that can help you tackle the root cause of weight gain and keep it off for the long term. That means:

• Eating a balanced, healthy diet that provides all the vitamins and minerals you need, while still giving you the flexibility to eat out and enjoy the foods you love in moderation
• Prioritising daily exercise and finding a style of movement that you enjoy (whether that's swimming, walking, cycling, or even gentle yoga or Pilates)
• Do your best to get a good night's sleep each night to ensure your body can rest and recover properly
• For those coming off a strict calorie deficit, approaches like reverse dieting can help reintroduce calories gradually to support metabolic recovery and reduce the risk of rapid weight regain

Extreme diets where you eat too few calories and fancy gimmicks are unlikely to lead to losing fat and maintaining healthy habits in the long term. Instead, balance is everything in diet and exercise habits.

If you need a hand kickstarting your health and weight loss journey, Pilot's Weight Reset Program helps you tackle excess weight from the inside out to set you up for success.

Learn to control hunger and cravings, target appetite, and eat less. Plus, with medical professionals at your fingertips, the program can help rewire your relationship with food to achieve sustainable weight loss.