When someone receives a diagnosis of a serious mental illness, such as schizophrenia or bipolar disorder, they face an alarming and often overlooked consequence: swift and significant weight gain. This rapid increase not only contributes to a heightened risk of diabetes and heart disease but also exacerbates the existing life expectancy gap for these individuals.

A groundbreaking study we conducted, recently published in The Lancet Psychiatry, tracked the health records of over 113,000 adults in the UK from 1998 to 2020. This marks the largest and longest investigation of its kind, uncovering that weight gain is not only frequent but also follows a predictable pattern.

For instance, a 39-year-old newly diagnosed with schizophrenia or bipolar disorder can expect to gain around 2kg in the first year alone, with predictions of approximately 5kg over five years. By the 15-year mark, this average weight increase climbs to about 5.5kg. Comparatively, individuals of the same demographic without a serious mental illness gained only about 1.5kg during the same timeframe.

Initially, we considered whether some early weight gain could signify a recovery phase—an appetite rebound following a period of acute illness. However, our findings revealed that most patients were already overweight at diagnosis and subsequently transitioned into obesity over the years. This indicates that the weight gain is sustained rather than a mere rebound.

This alarming trend is fueled by a combination of physiological and social factors. Antipsychotic medications, commonly prescribed to individuals with severe mental health conditions, can lead to changes in metabolism and appetite. In our study, those on antipsychotics experienced the most dramatic weight gain, averaging 5.9kg over 15 years. Even individuals who had never been prescribed these medications still saw significant weight increases, averaging 2.5kg.

Other factors contributing to this issue include social isolation, poverty, and inadequate access to nutritious food or exercise opportunities—critical data points that our study could not analyze due to limitations in GP records.

We also looked into whether individuals with serious mental illnesses received adequate support for weight management. Surprisingly, those who were overweight or obese were about 10% more likely to be advised to lose weight compared to the average overweight individual. Yet, they were less likely to be offered a referral to weight-loss programs: only 4.5% had any record of such a referral, while about 3% of those without mental illness received similar offers.

Individuals at high risk of chronic health issues are informed of the need to lose weight but are often left without the necessary support to do so. Community weight-loss initiatives can be effective, but without proper referrals, many remain unaware or unable to access these resources.

Mental health professionals often prioritize immediate psychiatric care, focusing on crisis management and symptom stabilization, leaving little room for preventive physical health measures. Conversely, GPs may hesitate to address weight issues in patients with complex mental health challenges.

This disconnect between policy and practice is evident. Although national initiatives like England's new 10-Year Health Plan emphasize cardiovascular health for those with serious mental illness, many continue to fall through the cracks.

Changing this pattern is crucial. Weight gain linked to serious mental illnesses is not a foregone conclusion; it’s measurable, predictable, and can be prevented with the right interventions.

Our research indicates that the period immediately following a diagnosis is a critical opportunity for action. Acting within the first five years could significantly decrease the risk of long-term obesity, diabetes, and heart disease, enhancing quality of life and potentially reducing the burden on healthcare systems grappling with rising chronic disease rates.

It’s essential to dispel the misconception that those with schizophrenia or bipolar disorder cannot lose weight. Effective interventions must begin early, utilizing evidence-based practices alongside consistent follow-ups. Community weight-loss groups should adapt to the individual’s evolving mental health status and barriers to accessing care.

Everyone deserves the chance for optimal physical health, and it is imperative that primary care and mental health services initiate weight assessments at diagnosis. Referring patients with serious mental illnesses to tailored weight-loss programs before rapid weight gains accelerate is vital for achieving the goals outlined in national cardiovascular prevention plans, especially in underserved communities.