Relevance of obesity in SMI

The prevalence of obesity is increasing worldwide, and has nearly tripled since 1975.¹ In England, 67% of men and 60% of women were classified as overweight or living with obesity in 2018.² Although the causes are multifactorial, there is a clear positive association between lower socioeconomic level and obesity.^{Reference Marmot3} The most commonly used method to assess health risks associated with high body weight is body mass index (BMI). In adults, obesity is defined as a BMI ≥30 kg/m².^1,4 A BMI of >30 kg/m² is a major risk factor for cardiovascular disease, diabetes and cancer, among other non-communicable diseases.¹

In those living with severe mental illness (SMI) such as schizophrenia and bipolar affective disorder, there are high prevalence rates of obesity and metabolic disorder (40–50% and 50%, respectively).^{Reference Lopresti and Drummond5} Additionally, people living with SMI have significantly lower life expectancy than the general population. A study from a secondary mental healthcare case register in London with 31 719 participants showed a reduction of approximately 12 years in life expectancy at birth in people living with any SMI.^{Reference Chang, Hayes, Perera, Broadbent, Fernandes and Lee6} Other studies have shown the same pattern of premature death and decades of potential life lost (averages varying from 13 to 30 years) among people living with SMI.^{Reference Chang, Hayes, Perera, Broadbent, Fernandes and Lee6,Reference Colton and Manderscheid7} Underlying causes for raised mortality in SMI may be multiple. Leading causes of death are cardiovascular disease, unintentional injuries and suicide. Obesity, hypertension, diabetes mellitus and chronic obstructive pulmonary disease are among the most prevalent medical comorbidities in this population. Factors likely to contribute to the development of these conditions are increased prevalence of smoking, increased substance use, inadequate social support, reduced physical activity and medication-induced weight gain.^{Reference Colton and Manderscheid7,Reference Miller, Paschall and Svendsen8}

Some antipsychotics might play a significant role in the development of metabolic syndrome, as they might cause glucose dysregulation, weight gain and lipid disturbance. The most efficacious antipsychotics, such as clozapine and olanzapine, seem to be associated with more weight gain and metabolic syndrome risk.^{Reference Pillinger, Mccutcheon, Vano, Mizuno, Arumuham and Hindley9,Reference Vancampfort, Stubbs, Mitchell, De Hert, Wampers and Ward10} Weight gain associated with antipsychotics can discourage patients from consistently taking their medication and, consequently, increase the chances of relapse. It is therefore important to have open and honest discussions with patients about these side-effects during the consultation. A non-judgemental approach is paramount to establish good rapport with patients. People who struggle with losing weight are often left with feelings of guilt and shame, as they feel blamed by healthcare practitioners. This can be a significant contributor to internalised stigma, which is known to reduce success with weight loss interventions and can negatively affect patients’ coping abilities and motivation to lose weight. Healthcare practitioners should be aware of the biological drivers to weight regain that make long-term weight loss difficult to achieve without bariatric surgery.^{Reference Malterud and Ulriksen11–Reference Halliday, Polsky, Schoen, Legget, Tregellas and Williamson13} Implementation of healthy weight management strategies as early as possible for individuals who are taking antipsychotic medication is also essential.^{Reference Allison, Mentor, Heo, Chandler, Cappelleri and Infante14} People living with SMI benefit from lifestyle changes targeting to reduce body weight, such as weight management counselling and group exercise, despite the use of psychotropic medication and ongoing psychiatric symptoms – factors which could potentially affect adherence to such methods.^{Reference Daumit, Dickerson, Wang, Dalcin, Jerome and Anderson15} Liraglutide, a glucagon-like peptide-1 receptor agonist, is associated with reduced body weight, improved glucose tolerance and reduction in systolic blood pressure and low-density lipoprotein levels, when compared with placebo, in patients living with SMI who are using antipsychotics.^{Reference Larsen, Vedtofte, Jakobsen, Jespersen, Jakobsen and Svensson16}

In addition, the accumulation of adipose tissue can influence hormonal and biochemical responses. Increased abdominal adiposity seems to be related to a greater response of the hypothalamic-pituitary-adrenal (HPA) axis and accumulation of cortisol in adipocytes.^{Reference Incollingo Rodriguez, Epel, White, Standen, Seckl and Tomiyama17} Social circumstances are also important contributing factors. Adverse childhood experiences, such as physical and sexual abuse, exposure to domestic violence and household mental illness, are strong predictors for development of health issues later in life. This includes heavy alcohol use, heart disease, cancer, obesity and mental ill health (including depression, anxiety and suicide attempt).^{Reference Hughes, Bellis, Hardcastle, Sethi, Butchart and Mikton18} These early-life stressors might also trigger the HPA axis, which can lead to metabolic changes.

Exploring root causes: take-home message for your clinical consultation

Understanding the mechanisms that drive people living with SMI to gain weight is a process that requires time and active listening, as it is often a non-linear path with periods of satisfactory weight control intercalated with periods of overeating. It is important to identify unhealthy eating patterns as a form of coping mechanism for stressful situations. Once this is recognised and acknowledged by the patient, it becomes an opportunity to find possible root causes and triggers, dissect these issues and explore alternative healthier coping mechanisms. During the consultation, assess the person's view of possible reasons for weight gain, their readiness to adopt changes and their confidence in making those changes. Ask about comorbidities (such as type 2 diabetes, cardiovascular disease, hypertension) and explore any psychological issues and eating behaviours,⁴ in view of screening for factors that might affect the success of treatment, such as alcohol misuse, intellectual disability and eating disorders (including binge eating disorder).

Treatment options for obesity

Considering all treatment options for obesity for people living with SMI is important, particularly when we contemplate the potential positive influence on quality of life that these interventions can offer. The National Institute for Health and Care Excellence (NICE) has outlined interventions according to a four-tier system (see Fig. 1), which consists of universal interventions, lifestyle weight management services, multidisciplinary clinically led team approach and, finally, bariatric surgery services. The choice of intervention should be agreed with the patient.^{Reference Avenell, Robertson, Skea, Jacobsen, Boyers and Cooper19} Lifestyle and behavioural interventions, as well as dietary and physical activity advice, are the base of treatment. One study conducted with patients living with SMI who had raised BMI and were participating in psychiatric rehabilitation programmes evidenced significant reduced weight in patients undergoing weight management counselling and group exercise over a period of 18 months. Despite psychotropic medication use and ongoing psychiatric symptoms, patients in the intervention group had a mean change in weight from baseline of −3.4 kg, compared with −0.2 kg in the control group at 18 months.^{Reference Daumit, Dickerson, Wang, Dalcin, Jerome and Anderson15} Pharmacological intervention is considered after dietary, exercise and behavioural changes were not sufficient to reach the targeted weight loss.⁴ The current licensed drugs are orlistat and liraglutide. The first is recommended for people with BMI >30 kg/m² or BMI >28 kg/m² with risk factors. The second can be prescribed by a physician as part of a tier 3 specialist weight management service, and it is intended for people with BMI of at least 35 kg/m² or at least 32.5 kg/m² for those of higher-risk ethnic groups, presence of non-diabetic hyperglycaemia and high risk of cardiovascular disease.^{Reference Avenell, Robertson, Skea, Jacobsen, Boyers and Cooper19,20} For people taking antipsychotics who experience weight gain and where non-pharmacological interventions/changing antipsychotic agents are not sufficient measures to reduce weight, metformin is the first choice of drug. It has positive effects in body weight, insulin resistance and lipid profile in people who are prescribed antipsychotic medication.^{Reference Mizuno, Suzuki, Nakagawa, Yoshida, Mimura and Fleischhacker21}

Fig. 1 Definition of the tiers and comissioning lead for weight management. Based on the Commissioning guidance for weight assessment and management in adults and children with severe complex obesity, 2018. (GP, general practitioner; MDT, multidisciplinary team)

Bariatric surgery is considered when BMI >35 kg/m² and comorbidities are present (such as type 2 diabetes and hypertension) or BMI >40 kg/m² without comorbidities. If the patient has recent-onset type 2 diabetes and a BMI of 30–34.9 kg/m², consider an assessment for bariatric surgery. Clinicians should also consider assessment for bariatric surgery for people with Asian family origin who have recent-onset type 2 diabetes at a lower BMI than other populations. Other inclusion criteria are commitment to the need of long-term follow-up and intensive management in a tier 3 service.²² Bariatric procedures result in greater weight loss than other forms of medical treatment for obesity, and can reduce incidence of diabetes,^{Reference Courcoulas, Yanovski, Bonds, Eggerman, Horlick and Staten23} potentially contributing to reducing cardiovascular risk factors.

Surgery for obesity should be undertaken by a multidisciplinary team that can provide a comprehensive pre-operative assessment (risk–benefit analysis, specialist assessment for eating disorders), psychological support and management of comorbidities.²² Clinicians should consider having a discussion with the mental health team around the patient's understanding of bariatric surgery, how they would cope in a tier 3/4 environment and what further support they would require after surgery. When referring to tier 2, 3 and 4 services, clinicians should be attentive to the patient's mental health needs that might take priority at that point or prevent them from engaging in treatments. However people living with SMI can do as well with community-led interventions as those without.^{Reference Cohen, Taveira, Wu and Pirraglia24} Care should be taken to guard against the risk of diagnostic overshadowing, where obesity is missed or not attended to because of the presence of SMI. General practitioners should progress through the tiers as soon as possible, being mindful that patient's poor engagement with services should not be an impediment to refer to tier 3 services. Usually, there is no exclusion criteria for referral for tier 2 services, although clinicians should avoid referring during a mental health crisis.

Although psychological support is included in NICE guidelines recommendations, guidelines for the provision of psychological support pre- and post-bariatric surgery has been difficult to implement because of a lack of resources. In 2019, the British Obesity Metabolic Surgery Society endorsed guideline suggests a stepped-care approach involving online resources, group workshops and one-to-one contact with a clinical psychologist. Which one of the three steps will be used is based on the issue presented by the patient and the potential impact if the issue is not addressed. It is recommended that all those seeking bariatric surgery have a psychological assessment triage, to identify the support they require to optimise weight loss and psychological outcomes.^{Reference Ogden, Ratcliffe and Snowdon-Carr25}

Follow-up after surgery

People who had bariatric surgery must be offered a follow-up package for a minimum of 2 years within the bariatric service, which should include support on diet, nutrition, physical activity and psychological support.^{22,Reference O'Kane, Parretti, Pinkney, Welbourn, Hughes and Mok26} It is recommended that all patients have a psychological screening assessment at 6 and 9 months post-surgery, applying the previously mentioned stepped-care approach to address any issues identified, although this is practically difficult to implement because of a lack of resources.^{Reference Ogden, Ratcliffe and Snowdon-Carr25} In people living with SMI, where the bariatric service does not have its own psychological support in place, planning post-operative review by the mental health team may support picking up post-operative issues if they arise. After discharge from bariatric surgery service, all patients should be offered annual monitoring in a shared-care model of chronic disease management.^{22,Reference O'Kane, Parretti, Pinkney, Welbourn, Hughes and Mok26}

A large retrospective cohort study involving 8000 patients was published in 2017, with the aim to evaluate if patients living with mental illness, particularly SMI, would have less weight loss and higher post-operative acute care use after bariatric surgery compared with patients with no mental illness. In this study, 57% of the patients selected had a mental health diagnosis in their records (before pre-operative evaluation) and the median follow-up was 2.9 years. Results from this large study showed that patients living with mental illness, even those living with SMI, had very similar weight loss compared with those with no mental illness pre-operatively, suggesting that patients with a history of mental illness can benefit equally from surgical treatment of obesity. However, pre-operative diagnosis of mental illness was predictive of greater acute care use, although the authors did not examine cause-specific healthcare use after surgery.^{Reference Fisher, Coleman, Arterburn, Fischer, Yamamoto and Young27}

Reflections and considerations

Recommended additional reading

1. 1. Teale KFH, Devine A, Stewart H, Harper NJH. The management of metformin overdose. Anaesthesia 2002; 53(7): 698–701.

2. 2. Every-Palmer S, Romans SE, Stubbs R, Tomlinson A, Gandhi S, Huthwaite M. Experiences of weight-loss surgery in people with serious mental illness: a qualitative study. Front Psychiatry 2020; 11: 419.

3. 3. Thompson L, Aveyard P, Jebb S, Blackshaw J, Coulton V, Tedstone A. Let's Talk About Weight: A Step-By-Step Guide to Brief Interventions with Adults for Health and Care Professionals. Public Health England, 2017 (https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/737903/weight_management_toolkit_Let_s_talk_about_weight.pdf).

4. 4. Scarpellini E, Arts J, Karamanolis G, Laurenius A, Siquini W, Suzuki H, et al. International consensus on the diagnosis and management of dumping syndrome. Nat Rev Endocrinol 2020; 16(8): 448–66.

About the authors

Carolina Pressanto is a Core Specialty Registrar in General Adult Community Mental Health Team with Kent and Medway NHS and Social Care Partnership Trust, UK. Samantha Scholtz is a Consultant Psychiatrist in bariatric surgery at the Imperial Weight Centre, St Mary's Hospital, Imperial College Healthcare NHS Trust, UK; and Research and Development Director at the West London NHS Trust, UK. Nasteha Ali is a lived experience author and a Patient and Public Representative at the R&D department, West London NHS Trust, UK.