The Truth About Your Metabolism |
Baffled by your metabolism? Whether you’re convinced yours is sluggish or are unsure as to whether hardcore workouts are really doing your body any favours, we went straight to the experts to find out the truth about how age, gender, exercise and supplements can affect your metabolism…
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Firstly – what exactly is the metabolism? 

“Your metabolism refers to the physical and chemical processes in the body which keep you functioning, including breathing, nerve function and blood circulation. To ensure you can carry out these processes, your body converts energy from the food you consume into fuel, which is either used immediately or stored in the body's tissues. The energy you expend over a day in order to survive is called your basal or resting metabolic rate (often referred to as BMR).” – David Wiener, Training & Nutrition Specialist at Freeletics

How much of your metabolism is genetic?

“It’s tricky to say. While the metabolic rate does vary between individuals it’s more likely down to factors such as age, muscle mass and activity levels as opposed to something genetic. However, some people are born with more muscular body types than others, and these people will naturally have a faster metabolism. There are also some genetic health problems which can impact your metabolism such as hypothyroidism which can cause decreased metabolism, or hyperthyroidism can cause increased metabolism – such issues can be genetic.” – David Wiener

What are the signs of a fast or slow metabolism?

“If you struggle to lose weight despite a having a healthy diet and working out on a regular basis, this could be a sign of a sluggish metabolism. Unexplained weight gain, tiredness, dry skin, hair loss, brittle nails and headaches can also be symptoms. Conversely, one of the main signs of a fast metabolism is being able to consume plenty of calories without putting on any weight.” – Jenna Hope, registered nutritionist

Are hormones linked to metabolism?

“Yes. There’s a wealth of research which suggests a link between hormones and metabolism. The main hormones involved in metabolic processes include insulin, glucagon, ghrelin (the hunger hormone) and the thyroid hormones as well as the stress hormone cortisol. Each of these hormones, and many more, impact on your metabolism and your body’s ability to burn fat. A healthy lifestyle which includes a good diet and plenty of exercise can help to regulate hormone production, emphasising the link between hormones and metabolism.”– David Wiener

Are there any lifestyle factors that affect metabolism?

“Absolutely. First and foremost, regular exercise is vital for a healthy metabolism – staying active will increase muscle mass and encourage your body to burn calories at a faster rate, even when at rest. With that in mind, an inactive lifestyle can negatively impact your metabolism. Similarly, certain aspects of your diet can also affect metabolism; for example, if you don’t eat enough iodine for optimal thyroid function, it can slow down your metabolism. Foods rich in iodine include cranberries, cheese, eggs and yoghurt.” – David Wiener

Can any supplements help boost metabolism?

“No, and don’t be lured by any supplements that claim to work miracles. The studies used to support the claims on many of these supplements are often done on animals where high doses are administered – this can be extremely dangerous to human consumers. These products also often come with unwanted side effects (such as laxative effects) and are best avoided. When it comes to nutrition and health, there is no magic cure and any supplement that sounds too good to be true probably is.” – Jenna Hope

Does the metabolism slow as you get older?

“Yes, but it’s a progressive change that happens over time and is triggered by hormonal shifts like the menopause. Your muscle mass also naturally declines as you age and this will have an effect on your metabolic rate.” – David Wiener

Is it true crash diets can affect metabolism?

“Absolutely. There’s research to suggest rapid weight loss and crash diets can slow your metabolism, leading to future weight gain – this is the body’s way of delaying starvation mode for as long as possible. Research has also suggested individuals who crash diet a lot in their younger years are more likely to have problems with their metabolism in later years.” – Jenna Hope

What about eating breakfast – is it true it fires up metabolism for the day?

“Yes and no. Research shows there’s no difference in metabolic rate between individuals who consume breakfast and those that don’t, so it’s really down to personal preference. If you find it fires you up for the day and means you’re less likely to snack mid-morning and reach for a healthier lunch then stick with it, but if you’re not hungry first thing then don’t beat yourself up about missing breakfast.” – Jenna Hope

And drinking water? Does staying hydrated really boost metabolism?

“Yes – dehydration causes your body's basic processes to slow down, eventually leading to a temporary decrease in your metabolism. When cells in the body are deprived of water, they shrink slightly; the body senses the change in cell size and uses it as a signal to slow metabolism. A recent study by the University of Utah found that when people experience 3% dehydration, their metabolism slows by around 2%.” – David Wiener

When it comes to exercise, what’s the best way to boost metabolism?

“There’s no doubt that staying active and building lean muscle is key to boosting metabolism – estimates suggest every pound of muscle burns around six calories per day at rest, which is around three times as many calories as a pound of fat, which burns roughly two calories per day. Countless studies have shown that HIIT trumps LISS (low intensity exercise such as walking or slow jogging) when it comes to fueling your metabolism – HIIT and strength training cause more physiological stress to the body, raising something called EPOC (excess post-exercise oxygen consumption), which allows your body to burn calories even when in a resting state. LISS, on the other hand, has been found to have insignificant EPOC effects, meaning there is little or no change to metabolic rate.” – David Wiener

Is it better to work out on an empty stomach? 

“Not necessarily. Some studies have found exercising in a fasted state can burn up to 20% more calories compared to exercising after eating. This is because once you eat, insulin (which regulates the breakdown of fat) increases in our body. According to some research, higher insulin levels have been shown to suppress fat metabolism by up to 22%. However, another study has suggested eating carbs before working out increases the post-exercise ‘after-burn’ effect more than the fasted state, meaning you’ll burn more calories throughout the day, not just during your sweat session.” – David Wiener

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