Your body performs millions of chemical functions to keep you alive. Together, these processes are known as your metabolism.
Your metabolism affects your body weight by influencing the amount of energy (calories) your body needs at any given point. So, if you consume more energy than your body needs, then the excess calories will be stored as fat. Indeed, many people who put on weight easily blame it on having a ‘slow metabolism’. However, it’s more likely that they need to make better food and exercise choices.
The biggest component of your metabolism – which uses 50–80 per cent of the energy you consume – is your basal metabolic rate (BMR). Your BMR is the energy your body burns to stay functioning at rest.
But what can affect your BMR and metabolism? Here are 10 factors:
- Your muscle mass – Since muscle requires more energy to function than fat, the more muscle tissue you carry, the more energy your body needs to use just to exist. That’s why it is important you regularly do some form of strength training, particularly as you age, since muscle mass steadily declines after around the age of 40.
- Age – As you get older, your metabolic rate usually becomes slower. This is due to muscle tissue loss as well as hormonal and neurological changes. On the other hand, when infants and children have growth spurts, their metabolism speeds up, as more energy is needed.
- Body size – People with bigger bodies generally have faster basal metabolic rates because they usually have larger internal organs and fluid volume to maintain. Taller people have a larger skin surface, which means their bodies may have to work harder to maintain a constant temperature.
- Gender – Because men usually have bigger bodies than women (see above), they generally have faster metabolisms.
- Genetics – This can also play a role in whether you have a slower or faster metabolism, and some genetic disorders can also affect your metabolism.
- Physical activity – Regular exercise increases muscle mass, particularly the weight-bearing kind, and aerobic exercise encourages your body to burn calories at a faster rate, even when at rest.
- Hormones – Hormonal imbalances caused by certain conditions, including hypo- and hyperthyroidism, can affect your metabolism.
- Environment – Did you know that the weather can also effect your metabolism? If it is very cold or very hot, your body has to work harder to maintain its normal temperature (37°C). This means your body uses more energy, and so your metabolic rate is increased.
- Drugs – Caffeine and nicotine can increase your metabolic rate, while some medicines, including some antidepressants and steroids, can contribute to weight gain regardless of what you eat.
- Diet – Certain foods can also affect your metabolism. For instance if you don’t have enough iodine for optimal thyroid function, it can slow down your metabolism. Whereas, eating protein and spicy foods, such as chilli, will boost your metabolism. Eating regularly (i.e. not skipping meals), will also help to keep your metabolic rate ticking.