Nutrition interventions, as part of programmes that include regular physical activity and quality sleep, are an important component of healthy weight management. The dietary patterns of people with schizophrenia or those at high risk for psychosis are typically high in energy mainly contributed from excess fat (particularly saturated fat) and low in fruits, vegetables, and dietary fibre [30–34]. These eating patterns contribute both to dietary energy excess and gut microbiome alterations [35], which lead to subsequent weight gain, risks of conditions such as heart disease, type 2 diabetes, osteoarthritis, and exacerbation of mental health symptoms.

The causes of overeating are multifactorial [36]. Genetics, which can affect metabolic rate and weight status, and physiologic factors (e.g. leptin, ghrelen, uncoupling proteins, beta-endorphins, neuropeptide Y, decreased blood glucose) can reduce satiety or increase hunger. Recurrent and frequent binge eating can cause significant weight gain, and food environments, which offer an abundance of good-tasting, cheap food, makes it difficult for susceptible individuals to avoid such overeating triggers. Night eating, where most food energy is consumed between 8 p.m. and 6 a.m., is another common contributor to overeating.

For those with schizophrenia, other condition-related determinants contribute to excess food intake. As in Amanda’s case, psychiatric medications such as the second-generation antipsychotics, are associated with metabolic side effects of weight gain, dyslipidemia, insulin resistance, susceptibility to type 2 diabetes, and metabolic syndrome ([37–40]), which may be coupled by an a priori increased risk of obesity that has been reported in schizophrenia [41, 42]. Structural factors such as the built environment that controls food availability and social barriers such as negative discrimination and stigma can also contribute to the etiology of overeating and excess weight. Individual factors such as a history of trauma, memory or cognitive impairment, food-related hallucinations or delusions, comorbid eating disturbances, poor condition self-management skills, proneness to food fads and use of natural health products, concurrent substance use, social avoidance, symptoms of depression, anxiety, and poor sleep, and determinants of health such as low socioeconomic status, and food insecurity can create barriers to health services access and behavioural interventions [43–48].

Figure 19.1 outlines an algorithm that may be used in the assessment and management of weight and nutrition for individuals such as Amanda. Her initial assessment would include examining health status, nutrition-related biochemical measures and genomic markers where feasible, medication and natural health product use, food intake and eating behaviours, anthropometric measurements (e.g. height, weight, waist and hip circumferences), and health determinants such as income, food security, and living situation. Subsequently, an individualized lifestyle intervention would be negotiated where the nutrition component would focus on reducing energy intake in the range of 500–600 cal/day and applying cognitive and behavioural techniques aimed at dietary restructuring. The recommended macronutrient composition would emphasize high complex carbohydrates with moderate fat and protein levels where total energy is distributed as 20–30 % fat, 55–60 % carbohydrates, and 15–20 % protein to help reduce weight and control LDL-cholesterol, blood triglycerides, and blood glucose levels [49, 50], even in the context of antipsychotic medication use [45, 51]. The minimum caloric level for women such as Amanda is 1000 cal/day; for men no less than 1200 kcal/day should be consumed to ensure all nutrient requirements are being met. If the individual’s food intake is not balanced and varied, then fibre and micronutrients such as zinc, calcium, iron, and vitamin B₁₂ may be lacking and supplementation may be required. Furthermore, should the person be pregnant or lactating, or have significant eating disturbances these lower calorie diets should be avoided. In designing a weight management plan for Amanda , a personalized non-complex approach is needed that incorporates three core strategies:

As is the case with Amanda , several condition specific factors should be considered in the management of weight. While for some the structure of a diet plan may be helpful, therapeutic interventions may be needed alone or as adjunct to a diet plan to help correct eating disturbances and manage weight. Although a number of strategies may be used, evidence is currently lacking about their utility in mental health populations. For those who do not connect with hunger or satiety cues, mindful and intuitive eating counselling can help promote awareness of bodily sensations, self-care, and valuing health more than appearance [53, 54]. Motivational interviewing can also be used as a tool in weight management to help the individual resolve ambivalence about eating behaviour change and build intrinsic motivation [55]. Cognitive behaviour therapy (CBT) is a core strategy that can be used to address binge eating and improve body image [56]. Dialectical behaviour therapy is a form of CBT often used in more complex cases that can facilitate learning and skills development such as emotion regulation and distress intolerance that improve abilities to manage negative affect adaptively [57]. Should cognitive-behavioural and dialectical behaviour therapies not be effective, an alternative is acceptance and commitment therapy that can help the person work toward valued goals and life directions [58]. For individuals with cognitive impairments, cognitive adaptive training (CAT) may be used to help overcome challenges such as initiating and sustaining task behaviour (e.g. preparing meals). Exemplars of CAT environmental supports include separating foods into bins labelled by day of the week, using checklists, lists outlining steps for food preparation, and electronic auditory prompts, as well as practicing shopping at grocery stores using a food list [59]. While mobile electronic devices are popular tools to facilitate and maintain weight loss among overweight and obese populations, evidence on their sustained benefit and utility in mental health populations is currently lacking [60].

Physical inactivity is itself a major cause of morbidity and mortality, and merits the same level of concern as other cardiovascular disease risk factors like smoking (e.g. [61]). Studies consistently highlight that individuals with schizophrenia are less active than the general population [62, 63]. This is reflected in the demonstration of significantly lower cardiorespiratory fitness among individuals with schizophrenia in comparison to the general population (e.g. [64]). Given the compelling evidence that regular physical activity is an effective preventative strategy against premature mortality, cardiovascular disease, stroke, hypertension, colon cancer, breast cancer, and type 2 diabetes for the general population [65], promoting physical activity is important irrespective of weight loss.

We have adapted a form of physical activity counselling that is designed to increase physical activity by addressing an individual’s needs, motivation, and barriers to activity [66]. Physical activity counselling draws from numerous theories of behaviour change including social cognitive theory and the transtheoretical model (TTM) [67, 68]. Social cognitive theory states that behaviour is influenced and influences both environmental and personal factors. Environmental factors include group structures, equipment, or various facilities. Personal factors include cognitions such as self-efficacy, mood, and attitudes. Together, these three determinants influence one another and form what is known as triadic reciprocal causation [67]. The TTM allows a clinician to assess whether an individual is ready to change a particular behaviour. Depending on their readiness to change, clients are placed into one of six stages: precontemplation (not considering changing behaviour), contemplation (intending to change behaviour in the next 6 months), preparation (intending to change behaviour in next 30 days), action (actively engaged in behaviour change for 6 months), maintenance (actively engaged in behaviour change for more than 6 months), and termination (actively engaged in behaviour change for more than 5 years). This then directs attention to those individuals who are contemplating or preparing to increase their physical activity. The TTM also provides stage specific strategies that strengthen a client’s self-efficacy and highlight the positive, rather than the negative, attributes of increasing physical activity. Self-efficacy has been shown to be an important mediator of physical activity behaviour change in people with schizophrenia [69].

The intervention was conducted over 2 months and included four 60 min weekly individual sessions that could be replicated:

Session one: Build rapport and gather knowledge. This first session provided an opportunity to assess current levels of physical activity and explore commitment to increasing physical activity. As a starting point, physical activity was assessed using the International Physical Activity Questionnaire (IPAQ; [70]). The IPAQ has previously been validated as a measure of physical activity behaviour for adults with schizophrenia [71]. Throughout the first session, various techniques were used to assess readiness to change. First, past, present, and future interests and physical activity were explored. Given Amanda’s prior interest in sport and exercise there is an excellent basis for establishing rapport. Additionally, confidence and importance scales were used to assess how confident each participant was about becoming more physically active and how important physical activity was to him or her [72, 73]. A similar approach could be taken in assessing interest in modifying dietary behaviour and a decision taken to focus on one or both behaviours. The first session provided a better understanding of why physical activity may or may not be important to the participant and what potential barriers existed. In addition to the confidence and importance scales, the participants completed a decisional balance exercise [72, 73]. This exercise helped participants explore and overcome their ambivalence to behaviour change by attempting to establish a discrepancy between the advantages and disadvantages of changing their behaviour.