Maybe you meant 2.5 cm or 25 mm.

The most common cause of bloat and distension is chronic constipation. The best way to determine if this is the cause is by increasing your fluid intake and intake of fiber-rich foods (fruits and veggies, grains, breads, cereal, etc). I know it may seem counterintuitive to treating bloat, but you should drink at least 8 glasses of water a day, as this will actually improve bloating by lessening constipation and diluting electrolytes that cause you to retain water. You should also avoid gas-causing foods, such as beans, broccoli, cauliflower, cabbage, sprouts, onions and garlic, carbonated drinks, and products that contain sorbitol, mannitol, and maltitol sweeteners.

As I mentioned, food allergy or intolerance problem may also be the cause of the problem, such as lactose intolerance, or gluten allergy. Such reactions can lead to bloating, fluid retention, constipation or diarrhea, and stomach distension.

Alternatively, chronic bloat may be related to a medical condition, such as Irritable Bowel Syndrome, which is a functional disorder of the intestines that leads to pain, bloating, swelling, and distension. Antispasmodics, such as Hyoscamine and Bentyl, are used for cramping pain, if you're experiencing that. Gas-forming foods that contain high carbs, fructose, lactose and sorbitol need to be avoided for obvious reasons. Additionally, certain antidepressants can be used to treat IBS in chronic cases, as they affect a chemical in the body that influences the motility of your intestines. A certain antibiotic called Rifaximin seems to work really well for controlling gas and bloating in IBS patients. Taking simethicone (as well as charcoal tablets) can further help with gas, and prokinetic drugs like cisapride can aid in movement of gas through the bowels.

Firstly, try to lower your carbohydrate and sodium intake, and stick to fresh foods rather than heavily processed ones. There are also a variety of diuretic pills available (both OTC and by prescription) if you feel you have a lot of excess water weight related to bloating. One of these is vitamin B6, and would be safe to take in appropriate doses. Others include fruits like melons and citrus, and vegetables such as leafy greens, celery, cucumber, watercress, lettuce, tomatoes, peppers, carrots and onions have potassium and are natural diuretics. It sounds counterintuitive, but do not reduce your water intake, and drink a good 8 glasses a day. Increasing exercise will also certainly help get rid of excess water and reduce feelings of gas and bloat. In addition to the suggestions above, begin a food diary, and monitor what you eat and when you experience the bloating symptoms. You may be able to find a correlation between your symptoms and certain types of food (which you can then avoid). If none of the above work after a while, further diagnostic tests would be indicated to make sure a more serious, underlying medical condition isn't the cause of these symptoms, such as an intestinal obstruction.

Seeing a gastroenterologist may be a good next step for you towards solving and improving this problem.

I hope this helps!