Your metabolism refers to the millions of chemical processes that keep your body alive and functioning.
It is related to weight because it influences the amount of energy your body needs at any given point. Take in more energy than you need, and the excess will be stored as fat.
Nonetheless many people are quick to blame a “slow metabolism” for their weight gain, when in fact they need to make better food choices and exercise choices.
The biggest component of your metabolism – accounting for 50 to 80 per cent of the energy used each day – is your basal metabolic rate (BMR), which is the energy your body burns just to maintain functioning at rest.
(Other influences include how much physical activity you do, and the 'thermic effect' of the food you eat - that is energy you use to digest and absorb your food.)
While there are many pills, supplements and foods that claim to boost metabolism and burn fat, most of these claims are unproven, says Tim Crowe, associate professor in nutrition at Deakin University.
Even if they did work, they might come with unintended side effects, such as increasing your heart rate, he says.
Nonetheless, it can be helpful to know what factors do affect your metabolism, as some of them are within your control. And even knowing you have factors you cannot control may nonetheless be useful as it can motivate you to take extra care to compensate for the issue, perhaps by being more vigilant about your diet and exercise.