Taking regular exercise is especially important as we get older and our metabolism slows down, making us more likely to put on weight.
NHS statistics on obesity show that, in 2009, more than two-thirds of women and three-quarters of men in the 55-74 age group were overweight or obese.
The only way to lose weight is to use up more energy that we take in, and a daily walk can help to burn off some of those calories.
Coronary Heart Disease Statistics 2010 show that 1 in 5 men and 1 in 8 women died from coronary heart disease (CHD) in 2008.
However, people who are physically active are at lower risk of CHD and walking for 30 minutes a day can help to keep your heart strong and reduce blood pressure.
High blood pressure is also a key risk factor for stroke, which usually affects people over the age of 65.
Dr Radha Modgil says: 'Walking helps increase heart rate, increases cardiac output and reduces the risk of heart disease and high blood pressure long-term.'
According to Cancer Research UK, cancer causes 1 in 4 of all deaths in the UK.
Physical activity is associated with a reduction in risk of some cancers and the most active individuals have around a 20% lower risk of developing colon, breast and womb cancer than the least active.
Dr Modgil says: “Certain studies show that walking seems to reduce the risk of cancer more than running or tennis."
Since 1996, the number of people diagnosed with diabetes has increased from 1.4 million to 2.6 million. Most of these cases are Type 2 diabetes, which is more likely to affect older people or those who are overweight or obese.
However, The Textbook of Diabetes says that regular activities, such as walking, can reduce the risk by 26%.
Dr Modgil says: “Walking and weight loss helps reduce central obesity which is a risk factor for developing type 2 diabetes.”
Walking can help to strengthen bones, helping to prevent the onset of osteoporosis, which makes bones brittle and more likely to break.
According to the National Osteoporosis Society, 1 in 2 women and 1 in 5 men over the age of 50 will break a bone largely due to osteoporosis.
Dr Modgil says: “It’s not just women who are at risk of osteoporosis. Men are affected by bone density loss too, and weight-bearing exercise, like walking, is a good way to help minimise this.”
Regular exercise will improve your mood and increase feelings of well-being - and it can even help to relieve depression and reduce stress and anxiety.
A survey carried out by the charity Mind found that 83% of people with mental health problems found that physical activity helped to lift their mood.
Walking can help you to remain active for longer, meaning that you are less likely to feel isolated or lonely.
Research has shown that regular exercise can reduce the risk of Alzheimer’s Disease by up to 40%. For those who already have dementia, it can slow down progression of the illness.
Scientists also believe that older people who walk 6 miles a week could avoid brain shrinkage and preserve memory later in life.
Dr Mogdil says: “Some studies suggest that regular exercise promotes the growth of new cells in the brain and improves cell and tissue repair mechanisms, reducing the risk of dementia.”