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Dietary advice is a routine part of the management of irritable bowel syndrome (IBS). If standard dietary advice is not efficient enough, a low-FODMAP (fermentable oligo-, di-, mono-saccharides and polyols) diet can be proposed. It consists of reducing foods rich in carbohydrates that can be malabsorbed, the fermentation of which can lead to digestive disorders. These include several dairy products, certain cereals, and many fruits and vegetables. Currently considered as the most effective diet in the management of IBS, low FODMAP can significantly reduce abdominal pain, bloating, and improves the patient’s quality of life. If this restrictive phase of four to six weeks significantly reduces the symptoms, it needs to be followed by a phase of gradual reintroduction and then by a phase of personalized diet with an adaptation of the FODMAP intake to the patient’s tolerance capacities. The reduction of FODMAP foods can vary in its strictness, adapted to the severity of the symptoms and the nutritional state of the patient. A strict diet is difficult to follow, can lead to weight loss, can increase the problems of anxiety related to food often present, and can produce a dysbiosis whose long-term effects are uncertain. Following it strictly in the long term is not recommended. No predictor of diet response has been clearly identified. Ideally carried out with the supervision of a dietician, it can also be performed using smartphone apps that help identify which foods to avoid. A simple reduction in FODMAP foods can be considered as a first-line treatment and can effectively reduce symptoms with limited inconvenience for the patient. A strict low-FODMAP diet should be offered as a second-line treatment if these initial measures are insufficient, and only in selected patients.