What does ‘metabolism’ mean?
Your metabolism refers to the chemical and physical processes that occur continuously inside the body, which keeps us functioning normally in order to stay alive. These processes include breathing, nerve function and blood circulation as well as the breakdown of nutrients from food and drink that is then converted to energy.
The largest component of your metabolism is your basal metabolic rate (BMR) – which is the amount of energy your body uses just to maintain functioning at rest. This surprisingly accounts for 50-70 percent of the energy used each day.
Other influences include the level of physical activity and the thermic effect of the food you consume (energy that is used to digest and absorb your food).
Why is our metabolism the fastest when we’re young?
When we are young, we are still growing and developing. This process requires a lot of energy and in turn, the body requires a lot more energy from food and beverages to support this process.
Another reason why our metabolism is faster when we are younger is because we are generally more active and have less fat mass compared to when we age.
Why does our metabolism slow with age?
As you get older, your metabolic rate generally slows because the ageing process results in a decrease in your muscle mass and an increase in the amount of fat stored. In addition, there are also a number of hormonal and neurological changes that take place, which will also have an effect on levels of stored fat.
Your BMR is partly determined by the amount of muscle you have because muscle burns a lot more calories compared to fat so when you lose muscle, your metabolic rate drops and you burn fewer calories. This would suggest that the more muscle you have, the higher your metabolic rate.
It is thought that your BMR decreases at one to two percent per decade after you reach the age of 20 and up to 10% per decade after the age of 45.
Is there anything we can do to prevent our metabolisms from slowing down?
Unfortunately, we cannot defy the process of aging so our metabolism will decline naturally as we age. However, there are some steps we can take now to optimise our metabolism in order for us to
Exercise – To increase your metabolism through physical activity, any form of cardiovascular exercise is good. However, high-intensity interval training (HIIT) can be particularly effective, due to the concept of “after-burn” – that is, an increase in resting metabolic rate that occurs for up to 24-hours post-exercise.
Weight/resistance training to build lean muscle mass is also important for optimal metabolism as muscle is more metabolically active than fat mass.
Sleep– If you get too little sleep, your metabolism slows down to conserve energy, which then triggers the release of the stress hormone cortisol. Having consistent high levels of cortisol increases fat cell growth and storage because visceral fat tissue contains a high number of cortisol receptors which responds to the circulating cortisol in the blood. As a result, this can negatively affect our metabolism.
Diet– As mentioned previously, higher levels of fat storage can impact negatively on our metabolism. Therefore, maintaining a healthy weight is optimum for a healthy metabolism. There are certain vitamin deficiencies that may contribute to fat metabolism, deposition and storage and those include:
- Vitamin D – Low levels of vitamin D result in your body producing certain hormones that are responsible for fat cells to hoard and store fat rather than burn it.
- Chromium – This mineral is responsible for the metabolism of fats, carbohydrates (particularly glucose), and insulin. People with a chromium deficiency are at risk of impaired glucose intolerance and therefore, type 2 diabetes.
- Magnesium – Magnesium is a co-factor of many enzymes involved in glucose metabolism. It has an important role in the action of insulin, and insulin stimulates magnesium uptake in insulin-sensitive tissues. Therefore, people with lower levels of magnesium may be at higher risk of insulin resistance, which causes fat to accumulate around the abdomen.
Furthermore, if you follow a strict diet with the premise of a low calorie intake, this may lead to nutrient deficiencies due to the risk of limited variety in food choices. Put simply, your body goes into ‘starvation mode’ when you eat less than you need for basic bodily function. Your body then puts the breaks on your metabolism meaning your body becomes very efficient at making the most of the calories it gets from the minimal food and drink.
Hormone balance – Metabolism is controlled by the thyroid gland in the neck, which in turn is governed by a part of the brain called the hypothalamus. The speed of your metabolism depends on complex chemical messages, which are sent to your brain by your body, telling it how much it needs to function optimally. If there is an imbalance with your thyroid hormones, this may slow your metabolism down. Therefore, it may be beneficial to get your (thyroid) hormones tested to make sure they are within optimal ranges.
- Avoid fad diets – these usually are very low or too low in total calories and eliminate certain food groups, which may place you at risk of nutrient deficiencies.
- Do consistent strength/resistance training.
- Add HIIT training to your cardio workouts.
- Reduce stress to avoid high levels of cortisol.
- Reduce alcohol consumption.
- Pump up the protein – your body digests protein more slowly than fat or carbohydrates, which makes you feel fuller for longer. A sufficient protein intake will also assist in building and preserving lean muscle mass.
- Add spice to your food e.g. chilli, cayenne pepper
- Avoid trans-fats – these fats bind to fat and liver cells, which may slow metabolism and increase inflammation in the body.
- Consume green tea – the active ingredient, catechin found in green tea may boost your metabolism.