By Liam Gilliver More than 6,000 people are diagnosed with stomach cancer in the UK each year, despite cases falling since the early 1990s. It is not known what exactly causes the disease, which is most common in those over the age of 75. However, lifestyle factors such as being overweight, drinking too much alcohol and smoking can increase your risk. In fact, Cancer Research says around 15 per cent of stomach cancers in the UK are linked to smoking tobacco. With any type of cancer, getting an early diagnosis is essential for treatment to be most effective. But, many side-effects of the diseas…