WEIGHT MANAGEMENT ∙ 3 minute read

How does metabolism affect weight loss?

By Joseph Lee | Medically reviewed by Dr Jaskirt Matharu

A food intake of 2500 calories a day for men, coupled with at least 150 minutes of moderate-intensity exercise each week, is recommended in order to maintain a healthy weight. Drop the calories and increase the exercise and the pounds will drop off too. But too much food and not enough physical activity results in weight gain.

The word metabolism is often thrown around when talking about weight loss, or an inability to lose weight. But is metabolism really the key to weight loss and how does metabolism help you to lose weight?

What is metabolism?

Let’s get this straight, the main function of metabolism is not to lose weight or for weight control. However, metabolism can influence whether our bodies lose or gain weight.

Metabolism refers to chemical reactions in every cell of any living organism. This process provides energy for making new organic material and provides energy for vital functions to support life, including growth, movement and cognition.

After we’ve consumed food, enzymes are used by our digestive system to either break proteins into amino acids, turn fats into fatty acids or transform complex carbohydrates into simple sugars. This enables the body to utilise or store energy.

Metabolism is a complex process involving two different activities happening simultaneously. These processes are essentially building up and breaking down energy. Anabolism, sometimes referred to as constructive metabolism, supports the growth of new cells by storing energy to be used later on. Catabolism, or destructive metabolism, produces energy needed for cellular activity, breaking down large carbohydrate and fat molecules to release energy.

You can think of destructive metabolism as your body’s internal thermostat dial. When it’s turned up, more fuel is needed and burned.

Is there a normal metabolism?

Slow metabolism. Fast metabolism. Eat-two-Whopper-Burgers-and-won’t-get-fat metabolism (although we don’t recommend that). People often link fast metabolism to weight loss and slow metabolism to weight gain.

Although the association between metabolism and weight management is not a myth, metabolic rate fluctuates from person to person. Not everybody’s metabolic rate is the same. Individual metabolism speeds are calculated through a formula called basal metabolic rate (BMR). 

BMR provides a measurement of the rate a person uses energy whilst they’re resting - this includes functions such as cell growth, hormone management, blood circulation and breathing.

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What causes a change in metabolism?

There is research to show that basal metabolic rate does not play a role in weight gain, however, slow metabolism often gets blamed for piling on the pounds. Having said that, someone with a low metabolism or a slower metabolic rate will burn fewer calories when they’re at rest, suggesting that there is still an argument for BMR to factor into weight management. 

So, apart from exercise and BMR, what causes men's metabolic rate to change?

Men are more likely to have less body fat and more muscle than females. As muscle requires more energy than fat, a male who weighs the same as a female will usually burn more calories.

Body composition and size
Those that are large in stature with larger areas of muscle mass will burn more calories even when they’re resting.

As your age increases, muscle mass usually decreases and fat makes up more of your overall body weight. This is where the middle-aged man belly comes into play, as calories are burnt at a slower pace the older you get.

Do health problems affect metabolism?

Hormones from your thyroid enable your body to burn fat, giving you energy. Because of its fat-burning power, the thyroid gland has a direct link to the speed of metabolism and, in turn, impacts your BMR. 

When someone has an underactive thyroid, their thyroid gland is not able to effectively produce hormones T3 and T4. In this instance, you’re likely to put on weight as your body can’t regulate metabolism properly. If you’re struggling with weight loss, testing the amount of T3 and T4 in your body is a good way of checking your thyroid is functioning properly. You can check for biomarkers that regulate metabolism with an at-home blood test.

In other serious health problems, such as type 2 diabetes, normal metabolic function is severely affected. People with type 2 diabetes struggle to metabolise glucose, which can lead to weight management problems. Research shows that an appetite for high-calorie foods and a low amount of physical activity is a key catalyst to developing obesity and type 2 diabetes.

How to increase your metabolism with food

Unfortunately, there are some seriously unhealthy ways of increasing your metabolism, such as ‘fat burner pills’ that contain the chemical sibutramine. This banned fat-burning substance has been found to have serious psychological side effects

But there are many more healthy ways of increasing your metabolism to help you shift unwanted body weight and speed up metabolism. This starts with food, some of which have natural metabolism-boosting chemicals and help with weight loss.

Get spicy with chilli 

Chilli peppers contain a chemical known as capsaicin, which could increase the rate your body burns calories. Many scientific studies have found that consuming a small amount of chilli (just one jalapeño a day) could support your body in metabolising an extra 50 calories. 

Keep mineral-rich foods in mind

Minerals are needed in order for your body to function. They’re vital for the thyroid gland and keeping the right levels of iron and selenium in your body. Eating iron and selenium-rich foods such as nuts, legumes and red meat can keep your thyroid ticking over nicely so that your metabolism doesn’t slow down. 

Pack the protein in

A high-protein diet could be the way to reduce body fat, shed unwanted weight and enable you to get a more lean body composition. Research shows that metabolic rate could be raised as much as 30% when eating protein-rich foods compared to around 5% for carbs and even less for fats. Foods full of protein, such as meat, fish, eggs, nuts and seeds also serve to lessen the drop-off in metabolism that can be experienced when people first go through weight loss, by allowing the body to retain its mass of muscle. 

The numan take

Whether you have a fast metabolism or slow metabolism, the path to healthy weight loss starts by getting the right balance of calorie intake and physical activity. Metabolism is a complex chemical process that enables humans to get energy from food to sustain their life. There are healthy ways to boost your metabolism through food, exercise and frequency of eating. However,  some factors such as individual basal metabolic rate, or disease, impact the speed and functionality of the metabolic process.