A bland diet is a regimented diet option that a physician can use to help optimize his or her patient's overall health condition. The bland diet is a useful modality to employ when managing a patient with persistent gastrointestinal complaints, acid-peptic disease, excess gas formation or in certain postsurgical patients. The bland diet is sometimes referred to as a "low residue diet" or "soft diet." A bland diet is easier to break down and digest, therefore it gives rest to the gastrointestinal tract. It is also less acidic and causes fewer bowel movements. 
The bland diet comprises of easily digestible foods that are soft-consistency, low-fiber, cooked, gentle to the gastrointestinal tract and usually non-spicy. A typical such diet includes, but is not limited to, low-fat dairy products, eggs, broth, pudding, fruit juices, cream of wheat, tofu, lean meat (skinless chicken, fish,...), bland vegetables (beet, bean, spinach, carrot,...), eggs, and tea. The diet also eliminates raw or uncooked foods.
What is avoided in this diet is typically anything "non-bland." This might include fried food, spices, seeds and nuts, acidic fruits (berries, grapes, oranges, lemons, limes,...), whole-grain bread (wheat, whole wheat pasta, cereal,...), fatty dairy food (whole milk, whipped cream, ice-cream,...), non-lean meat (beef, fried fish, chicken with attached skin), dressings and sauces, pickles, alcoholic beverages, strong cheeses, and vegetables that cause excesses flatulence (cabbage, cauliflower, onion, pepper...).
Avoiding some of these elements will change the taste of the foods and affect our pattern of eating. There is no easy answer or solution for this, but some changes and substitution might ease the difficulties. Some raw fruits can be substituted with pureed fruits and compotes; nuts can be replaced with nut butter, nutmeg with cinnamon,...; Broiling or mashing some foods, rather than frying them, might be quite helpful. Beverages are habitual and can easily be substituted. Fruit water or tea can replace soda, coffee, and energy drinks.
The bland diet is most useful in adjunct to lifestyle modifications for a patient that struggles with gastric or duodenal ulcers, gastroesophageal reflux disease (GERD), excess flatulence, food poisoning, gastroenteritis, traveler's diarrhea, inflammatory bowel disease, diverticulosis or heartburn. It may be utilized in a patient before colonic procedures like colonoscopy.  Also, the bland diet is a viable option after stomach and intestinal surgeries when the patient is being transitioned back to a regular diet. The bland diet is mostly a temporary measure and not a permanent one.
Issues of Concern
Several barriers could prevent a patient from adhering to the bland diet. First, many patients may find the overall texture and lack of seasoning not palatable and unsatisfying. To follow the diet correctly, there are certain items a patient must take special care to avoid. The patient should avoid or strictly limit alcohol and caffeine consumption as these components can cause worsening of a patient's reflux symptoms by causing the lower esophageal sphincter to relax. There is a linear relationship between alcohol consumption and increased risk of worsening reflux or developing GERD. Any known food that will cause the lower esophageal sphincter to relax such as peppermint, chocolate, spicy foods, garlic, tomatoes, and some citrus can also worsen reflux and cause gastrointestinal complaints. Patient compliance at home with eliminating or minimizing these items consumption is essential for adherence to a proper bland diet.
Like any other diets, strict attention to portion control and multiple frequent low volume eating (as opposed to infrequent big-volume late-night meals) is of prime importance. It is very rare that dieting -or bland diets- cause nutritional deficiencies. This can only happen with extreme measures. Eating slowly and avoidance of lying down soon after eating is strongly recommended. Chewing slowly and not going to bed less than 3 hours after eating are of prime importance. If you are eating it and it makes you feel tired, weird, uncomfortable, gassy,...; don't eat it anymore. 
A bland diet is a useful tool in the process of advancing the diet after surgery and might be a new permanent diet. The soft, low fiber, easily digestible foods create less stress on the GI tract and allow it to heal more effectively. Furthermore, specific patient populations, like post-gastric bypass patients, also have a new lifestyle and mode of eating to which they must adhere to so that to decrease the risk of complication and help facilitate long term weight loss. The bland diet is a useful tool in this regard and can be a good starting point while counseling patients about dietary modifications. A bland diet is designed primarily to help patients recover from gastrointestinal conditions or surgeries in which gentle digestion would be beneficial. However, it is not as effective as the sole long-term weight loss diet solution. The bland diet must be used along with strict portion size control to achieve an initial weight loss goal. Overall, the bland diet is an excellent choice for patients that have gastrointestinal complaints or are post-surgical.
Most patients have a pre-existing knowledge that when they are having gastrointestinal complaints such as nausea and vomiting, they should limit food intake to a BRAT diet. A BRAT diet is bananas, rice, applesauce, and toast. However, most people do not understand that this is not synonymous with a bland diet. A bland diet is more extensive and focuses on decreasing the amount of work required by the entire GI system. In addition to the foods included in the bland diet, it also requires the total elimination of certain foods from a patient's food intake. Fried and high-fat foods, strong cheeses, and whole grains need to be eliminated or minimally consumed. Additionally, medications like aspirin and ibuprofen are to be avoided or minimized while on this diet to decrease gastric ulcer formation risk. Postoperative patients that have undergone esophagus, stomach, or intestinal based surgical procedures can also benefit from the bland diet.
Although all these might be true and common sense, there is little in the shape of actual factual evidence and clinical trials confirming it. Clinical trials of this sort (to focus on diets and specific elimination and inclusion) are notoriously hard to perform and can be costly and prone to confounding. Nevertheless, it is a potentially good area for possible research, and it is a "sexy" topic since almost all humans are interested in food intake and different kinds of food.