Bipolar disorders are found in two to three percent of the population and are characterized by periods of mania and depression. Without treatment, the disorder is often serious and disabling, but with the support of medication and educational and psychological treatment, most people can live a normal life. However, we warn about the consequences of the large increases and high levels of obesity in bipolar disorders. This concerns not only a poorer prognosis of cardiovascular disease, osteoarthritis, asthma, several forms of cancer and the risk of failed antibiotic treatment. In addition to the general negative effects, obesity has also been linked to a poorer response to antidepressants and to treatment with lithium and valproate in individuals with bipolar disorders. Obesity also aggravates the overall prognosis of bipolar disorders by increasing the likelihood of relapse and the severity of episodes with oscillating mood.