People breathe more easily and cough less when they give up smoking because their lung capacity improves by up to 10% within nine months.
In your 20s and 30s, the effect of smoking on your lung capacity may not be noticeable until you go for a run, but lung capacity naturally diminishes with age.
In later years, having maximum lung capacity can mean the difference between having an active, healthy older age or wheezing when you go for a walk or climb the stairs.
Within two to twelve weeks of stopping smoking, your blood circulation improves. This makes all physical activity, including walking and running much easier.
You'll also give a boost to your immune system, making it easier to fight off colds and flu. The increase in oxygen in the body can also reduce tiredness and the likelihood of headaches.
When you stop smoking, your senses of smell and taste get a boost.
You may notice that food tastes and smells different as your mouth and nose recover from being dulled by the hundreds of toxic chemicals found in cigarettes.
By stopping smoking, you'll be protecting the health of your non-smoking friends and family too.
Breathing in secondhand smoke increases the risk of lung cancer, heart disease and stroke.
In children, it doubles the risk of getting chest illnesses, including pneumonia, ear infections, wheezing and asthma.
They also have three times the risk of getting lung cancer in later life compared with children who live with non-smokers.