Addressing Rapid Weight Gain in Serious Mental Illness: The Need for Better Support

Individuals diagnosed with serious mental illnesses such as schizophrenia or bipolar disorder often face an underrecognized challenge: rapid and persistent weight gain. This side effect significantly elevates their risk for developing conditions like diabetes, heart disease, and even increases the likelihood of premature death, thereby widening the existing life expectancy gap.

A comprehensive study, published in The Lancet Psychiatry, examined the health records of over 113,000 adults in the UK from 1998 to 2020. The findings reveal that weight gain after diagnosis is not only common but also predictable. For instance, a typical 39-year-old newly diagnosed with schizophrenia or bipolar disorder can expect to gain about 2kg within the first year and approximately 5kg over five years. Over a span of fifteen years, the average weight increase reaches around 5.5kg. In stark contrast, individuals of similar age and gender without serious mental illness tend to gain only about 1.5kg in the same period.

Initially, researchers considered whether initial weight gain might be a recovery-related rebound as patients regain their appetite following acute episodes. However, most patients were already overweight at diagnosis, and continued weight increases led many to become obese, indicating a sustained, long-term trend rather than a rebound.

The pattern of weight gain is influenced by physiological factors and social determinants. Certain medications, particularly antipsychotics, are known to alter metabolism and increase appetite, contributing to the greatest weight increases—averaging nearly 6kg over fifteen years for those on such drugs. Yet, even patients not prescribed these medications experienced significant weight gain, averaging 2.5kg, highlighting the roles of social factors such as social isolation, poverty, limited access to healthy food, lack of physical activity, and disrupted routines—all of which BP records cannot fully capture.

Despite the increased health risks, there's a troubling gap in support for weight management. Patients with schizophrenia or bipolar disorder who are overweight are only slightly more likely to be advised to lose weight compared to the general population, and less than 5% are referred to weight-loss services. This lack of targeted intervention persists despite clear evidence that early, tailored support can prevent long-term obesity, diabetes, and heart disease.

Mental health professionals often focus on immediate psychiatric stabilization, leaving physical health care secondary. Meanwhile, primary care providers may feel unsure about addressing weight issues with patients who have complex mental health needs. Consequently, policies advocating for integrated physical and mental health care often fall short in everyday practice, both in the UK and internationally.

The findings underscore that weight gain after a diagnosis of serious mental illness is predictable, measurable, and preventable. The first five years following diagnosis constitute a crucial window for intervention. Early support through evidence-based programs, regular monitoring, and personalized care can significantly reduce the risk of long-term health complications and improve quality of life.

It's essential to dispel misconceptions that weight loss isn't possible for these patients. With proper early intervention and ongoing support, people with mental illnesses can achieve and maintain healthy weights. Healthcare systems must prioritize routine weight assessment at diagnosis and facilitate timely referrals to appropriate weight management programs, addressing the physical health disparities that these populations face.

Addressing this gap is vital to fulfilling national health objectives for cardiovascular prevention and reducing health inequalities among vulnerable groups, ultimately promoting better overall health outcomes for individuals with serious mental illness.