18. Obesity
Linda Hindle and David Kendrick
LEARNING OBJECTIVES
Readers of this chapter will gain an appreciation of:
• The physical and psychological causes and consequences of obesity;
• The importance of assessment for weight management;
• Evidence-based approaches to the dietetic treatment of obesity;
• A psychological approach to weight management; and
• The use of drugs and surgery to manage obesity.
Background
The prevalence of obesity is increasing such that over half the population are now overweight or obese. 1,2 This has significant health consequences, causing an increase in the risk of diabetes, coronary heart disease and certain cancers. 3 In 2008 the UK Government’s Foresight programme commissioned a report to project the future growth of obesity rates through to 2050 and to predict the consequences for health, health costs and life expectancy. 4 The worrying results estimate that by 2050, 60% of males and 50% of females and about 25% of all children under 16 will be obese. There is now considerable political, media and public focus on obesity and clear targets for the reduction of obesity. Governments across the world are setting targets and policies to stem the rising tide of obesity. Within this context, dietitians are in a key position to contribute to addressing the problem of obesity.
During the 1980s dietitians approached the treatment of obesity primarily from a technical perspective, taking the view that in order to lose weight people just needed information. In 1994 the Health Education Authority launched Helping People Change based on Prochaska and DiClemetes’ Stages of Change Model. 5,6 This led dietitians to develop a patient-centred approach for the treatment of obesity as they began to understand the psychology of behaviour change and appreciate why changing lifestyles to lose weight is not as simple as following instructions in a diet sheet.
Nowadays obesity is seen as a specialist area. Many dietitians have developed skills in motivational interviewing, counselling and cognitive behavioural therapy (CBT) in order to support patients to lose weight. Medication is now available as an adjunct to dietetic advice and dietitians are working with patients who are undergoing surgery to manage their weight. 7 There has also been an expansion in the role of pubic health dietitians with the recognition of the importance of the prevention of obesity. 8,9
Physiology
Obesity occurs when a person puts on weight to the point that it seriously endangers health. Obesity is defined in terms of body mass index (BMI), which is a measure of body fat based on height and weight (Table 18.1).
| Classification | BMI (kg/m 2) | BMI (kg/m 2) Asian origin11 | Risk of comorbidities |
|---|---|---|---|
| Underweight | < 18.5 | < 18.5 | Low (but risk of other clinical problems increased) |
| Normal range | 18.5–24.9 | 18.5–22.9 | Average |
| Overweight | 25.0–29.9 | 23–27.4 | Increased risk |
| Obese class I | 30.0–34.9 | 27.5–32.4 | Moderate |
| Obese class II | 35.0–39.9 | 32.5–37.4 | Severe |
| Obese class III | > 40.0 | > 37.5 | Morbid obesity |
Obesity in children and adolescents is normally defined in clinical practice as a sex- and age-specific BMI at or above the 98th percentile based on 1990 BMI percentile classification charts (91st percentile for overweight). 8 When population data are collected children are defined as obese if their BMI is > 95th percentile of the reference curve for age.
Although BMI is commonly used to assess the health risks associated with obesity, research suggests that measuring the waist circumference or waist-to-hip ratio is also a reliable method of estimating the health risks associated with an increase in weight (intra-abdominal fat mass). 10 This measure may also be more appropriate for Asian communities (Table 18.2). 8
| Men | Asian men | Women | Asian women | |
|---|---|---|---|---|
| Waist circumference | ||||
| Increased risk | ≥ 94 cm | ≥ 80 cm | ||
| Substantially increased risk | ≥ 102 cm | ≥ 90 cm | ≥ 88 cm | ≥ 80 cm |
| Waist-to-hip ratio | ||||
| Increased risk | ≥ 1.0 | ≥ 0.87 | ||
Some people are more genetically susceptible to obesity, but the basic cause of obesity is consuming more calories (units of energy) from food and drink than are expended in everyday activity. Most evidence suggests that the main reason for the rising levels of obesity is changing eating habits and less active lifestyles.
Psychological factors can play a significant part in the development and maintenance of obesity. These may include anxiety, depression, trauma and prolonged distress, low self-esteem and psychosocial problems.
Understanding the health consequences of obesity
Obesity is an important risk factor for many chronic diseases and the psychological and social burden of obesity can be significant. Social stigma, low self-esteem and a generally poorer quality of life are common experiences for many obese people. 12
Estimates of relative risk give a broad indication of the strength of the association between obesity and the secondary disease types listed in Table 18.3, although the BMI range used to estimate risk varies between studies.
| Disease | Relative risk | |
|---|---|---|
| Men | Women | |
| Myocardial infarction | 1.5 | 3.2 |
| Type 2 diabetes | 5.2 | 12.7 |
| Hypertension | 2.6 | 4.2 |
| Stroke | 1.3 | 1.3 |
| Cancer of colon | 3.0 | 2.7 |
A weight loss of 10% will potentially bring significant health benefits for obese people with corresponding reductions in blood pressure, lipid profiles and blood sugars.
Understanding the psychological and social consequences of obesity
Lack of understanding of the problems facing the obese is a serious problem. It is certainly fair to say that our society has a very negative view of people who are seen as being ‘fat’. One of these problems is intense prejudice or discrimination which cuts across age, sex, religion, race and socioeconomic status, and can be experienced at school, in the workplace and in family and social situations.
Therefore, it is important for us to understand the social and psychological consequences of obesity if we are to successfully help treat the problem. Research evidence of stigma and discrimination agrees with the public values and attitudes commonly expressed by the media. They tell us that being fat is an extremely unattractive and undesirable way to be, indeed, that it is a state to be avoided at all costs. Obese women are less likely to find employment, more likely to have their performance rated negatively and less likely to be promoted. 13
The perception of obesity
This derogatory view of obesity is not new. Some of the earliest research, published in the 1960s, examined children’s attitudes, presumably because they tend to reflect prevailing adult opinion. In one of these studies 10- and 11-year-olds were presented with six line drawings of a child as physically normal and with each of five physical disabilities, one being overweight. Ranking the figures by asking which they liked best resulted in a robust order of preference, with the normal child at the top, and the overweight child at the bottom, below that of a child with facial disfigurement, in leg brace and crutches or in a wheelchair. In a second study children were asked to assign 39 adjectives to one of three silhouette drawings depicting a thin, a muscular and a fat body shape. The obese body shape was least frequently assigned as best friends, most frequently gets teased, and labelled as lazy, dirty, stupid, ugly, liars and cheats more often than the other body shapes. 14
These two studies are important since they describe two principal features of the stigma of overweight. On one hand is the stigmatisation of bodily appearance; obesity is a highly visible but undesirable state. On the other is the stigmatisation of character; the moral view that holds the obese personally responsible for their own state and so blames them for their fatness. 15
Cognitive behavioural features of obesity
One of the basic premises of cognitive behavioural psychology is that there is causal inter-relationship between the way a person thinks (cognition) and what they do (behaviour). Neither the cognition nor the behaviour has the dominant causal role; either can be responsible for eliciting the other at any time. 16 This relationship between thinking and doing can be very complex and difficult to understand, particularly by those who know they are engaging in maladaptive behaviour (e.g. overeating), leading to unwanted products of that behaviour (e.g. weight gain, diabetes), but can not seem to control the ‘urge’ or ‘need’ to do so.
The aim of a thorough cognitive behavioural assessment is to get as much information as possible about the behaviour under investigation and what the links are between the way the person thinks and behaves. The outcome of this assessment should lead the investigator to propose a functional analysis of the problem which focuses on explaining ‘why’ the person behaves the way they do. Once this is understood it is possible to give the client insight into the links between their own thinking and behaviour, which will hopefully better equip them to deal with the problems they are experiencing.
For instance, most people who are morbidly obese have tried to lose weight by a variety of dietary constraints and/or pharmacological methods. They have often been successful in losing weight, only then to regain it plus ‘interest’! This subsequently leads to demoralisation over these ‘failed’ attempts to manage their obesity. It is important to understand how the individual handles this demoralisation in order to give them advice on how to plan their current/future attempt at weight loss by changing the ‘rules’ of their weight loss strategy.
It is similarly important to understand whether the person equates morbid obesity to a ‘personal defect’ or a ‘behavioural problem’.
If it is seen as a personal defect, many compensate for this by overextending themselves at home, at work or with friends. They may have a tendency to take care of other people at the expense of their own health and well being, often assuming a ‘caretaker’ role, putting the needs of others above their needs, and being unable or unwilling to ask for help for themselves. Explaining and getting them to accept that obesity can be viewed as a behavioural problem rather than a character defect can increase the likelihood of successful weight loss and maintenance.
Finally, to what extent do they have control over their environment? Feeling helpless (or without control over one’s environment) increases the risk for anxiety, depression and treatment non-adherence. 17
Binge eating disorder
Binge-eating disorder (BED) is characterised by recurrent binge-eating episodes, without the compensatory weight control methods found in bulimia nervosa. Although obesity is not a criterion for BED, it is a condition frequently associated with this diagnosis. Compared to matched obese subjects who do not binge, obese binge-eaters experience higher levels of general and eating-related psychopathology. For example, they show more concerns with body shape, and some authors found that binge-eating is significantly correlated with the perception that body weight is above the ideal. 18
Utilisation of social support
Research suggests that, for medical patients, social support is positively related to faster recovery and negatively related to premature mortality. Social support is also related to successful weight loss for people attending a general behavioural weight loss programme. 19
It would appear that some patients are especially susceptible to weight regain when faced with adversity that distracts them from attending to self-management guidelines. Clinically, we see maladaptive eating behaviour (whether stress eating, emotional eating, binge eating or night eating) associated frequently with poor stress management and with an inability to effectively self-modulate intense emotions or internal sensations of arousal (whether positive or negative). A careful assessment of their ability to cope both with negative stressors (uncertainty, frustration, deadlines, depressed mood, anger, anxiety or boredom) and with positive stressors (a pay-rise, a promotion, a party or holiday) may indicate whether they need specific intervention to enable them to handle stress better and therefore increase the likelihood of successful weight control, and avoid simply substituting one maladaptive coping behaviour (eating) with another (e.g. alcohol or drug abuse).
Compliance with medical treatment and adherence to self-management regimens currently and in the past are indicators of the patient’s potential attitude toward treatment. 20
Nutritional therapy and dietetic application
Much about the management of obesity relates to the approach taken by the practitioner and the relationship established between the practitioner and client. Therefore the assessment, approach and interpersonal skills of the practitioner are key elements to successful weight management.
Assessment
It is well recognised that one size does not fit all when it comes to what will help someone to lose weight. The diet trials study followed participants on one of four commercially available weight management programmes (Weight Watchers, Slim Fast, Atkins Diet, Rosemary Conley). 21 The authors concluded that each approach could work effectively provided the client chose the approach most suited to their lifestyle and preferences. A thorough assessment is required to enable the therapist and client to identify the approach most likely to be effective. The assessment gives the client an opportunity to self-reflect and identify enablers and barriers and gives the therapist an understanding of the client’s lifestyle, previous experiences of weight loss, history of weight gain, social circumstances and relationship with food.
The assessment is an opportunity to develop a rapport with the client and to demonstrate empathy in order that the client will have trust and confidence in the therapist’s ability to support them to lose weight; therefore the assessment appointment must be relaxed and not feel like an interrogation.
Interviewer skills
The ‘interviewer’ must have a goal-directed, focused approach and needs to develop specific skills in order to overcome the patient’s ambivalence or lack of resolve. This is one of the main obstacles that must be overcome if the person is to bring about the behavioural changes they need to ensure successful weight loss and maintenance.
Problem eating behaviour often takes the form of a conflict between the benefits and costs of both eating and restraint. It is important to attempt to get clients to identify, articulate and resolve this ambiguity, allowing them the opportunity to express (perhaps for the first time) the often confusing, contradictory and very personal feelings they have about themselves and their behaviour.
Direct persuasion is generally not an effective method of trying to resolve these issues. This may have been tried by family and friends attempting to be helpful, but tends to lead to the person becoming more resistant to change, resenting the help and the helpers, and increasing their belief in their own weakness. This in turn leads to more of the compensatory behaviour (i.e. eating).
The relationship between the client and the interviewer is very important and involves mutual respect. The person-centred approach allows the client to have their autonomy and freedom of choice. The client should respect the interviewer’s expertise in the field but not feel as if they are in a purely recipient role. It is possible to develop this relationship in just one session provided the interviewer is well trained and experienced.
In summary, the primary intention of this type of motivational interviewing is to increase the client’s readiness for change by allowing the client the opportunity to elaborate how they perceive the current situation. The skilled interviewer needs to be able to identify what the current conflicts are (discriminating between the critical and trivial issues), and then direct the person towards self-identification and subsequent problem solving. This gives the client ‘ownership’ of both the problem and its solution. They may need some form of intervention (e.g. skills training, cognitive restructuring, psycho-education) to enable them to satisfactorily resolve the problem but this is a secondary step to the initial phase of problem identification.
More directive or confrontational approaches should not be ruled out as motivational techniques. Some clients do respond well to having their beliefs confronted and deconstructed and alternatives proposed by the person carrying out the interview. They may not have had anyone able or willing to question their beliefs in a constructive way before. Use of logic, scientific facts and rationalising alternative thinking patterns can lead to the client being faced with information which is both novel and informative. This can be enlightening and give the client hope that there may be alternative strategies which they had not thought of and therefore may lead to an increased optimism of success.
The assessment interview will not necessarily follow any particular order; the flow will be determined by the client. However, the aim will be to cover the issues outlined below:
• History of weight gain;
• How the individual’s weight or current eating habits are impacting on their life;
• Understanding of the client’s social circumstances;
• What support the client has;
• Previous experiences of trying to lose weight;
• The client’s realistic expectations, if any;
• Motivation and confidence to make lifestyle changes;
• Activity level;
• Comorbidities and medication;
• Measurements of weight, height, BMI and waist circumference; and
• Dietary assessment.
At the beginning as with all dietetic consultations, introduce yourself, set the scene by clarifying the purpose of the session with the client and explain how long the appointment will take. The room setup is important: clients should feel comfortable and care should be taken that seating is appropriate for obese clients by avoiding chairs with arms or chairs that are too low.
A traditional diet history or 24-hour recall may not provide the most useful information about a client’s eating habits. Overweight and obese clients are known to under-report their intake by as much as 30–50%. 22 Overweight people may feel that they will be judged and therefore may not divulge the amount they eat. Equally they may not be fully aware of what they regularly consume. Overeating is usually associated with feelings of guilt which makes sharing this difficult. Asking about patterns rather than specifics can result in a more enlightening response. Questions that may be useful include:
• Are there any foods that are a problem for you?/If you were to overeat, what foods would you generally choose?
• Are there any times of the day when it is more difficult for you to control your eating?
• Do you eat regularly?/Do you ever miss meals?
• Do you tend to eat in response to emotions such as anger, being upset or because you are bored?
• Do you ever feel that your eating is out of control/feel that you can’t stop eating?
• Do you ever get up in the middle of the night to eat?
• Do you ever use laxatives or vomiting in an attempt to control your weight?
• How would you describe your portion sizes?
• How frequently do you eat out or have takeaways?
• What do you usually drink (including alcohol)?
• What do you think is the reason you are gaining weight?
The information obtained from this method of questioning will enable the therapist and client to identify key problems to be addressed such as irregular meals, snacking, types of food consumed and binge eating. The use of a food diary may give more detail if the client is able to complete it in adequate detail. This can be useful for refining advice at a later date but is not generally required initially.
A thorough assessment will require at least 45 minutes to do well.
Dietetic therapy
The dietetic approach chosen will be driven by the outcomes of the assessment.
There is no one size fits all with respect to choosing a weight loss approach; however, there are a number of principles supported by the evidence that are most likely to result in a successful outcome. These are described below.
Combination of diet, activity and behaviour modification
Weight management programmes that combine diet and physical activity treatments with behaviour modification support are most effective at supporting people to lose weight. 7 Approaches that focus on only one lifestyle element are less likely to support long-term weight loss.
Importance of regular meals
Many people struggling to control their weight follow an erratic meal pattern, frequently missing meals. This may be as a conscious effort to diet or restrain eating or as a lifestyle choice or habit. Ignoring internal hunger cues in order to stick to a diet may disrupt normal caloric regulation as demonstrated in Keys’ starvation studies. 23 These studies of conscientious objectors during World War II highlighted the impact of prolonged calorie restriction. The participants underwent experimental starvation to reduce their weight by 25% followed by a refeeding programme. As a result of the starvation phase, they became more obsessed by food (hording food, eating very slowly and taking interest in cookery books) and during the period of refeeding, many became disinhibited and ‘lost control’ of their eating, consuming large quantities without feeling satiated. It has been suggested that habitual dieters display marked overcompensation in eating behaviour similar to binge eating observed in eating disorders. 24 By the same mechanisms, dieters who frequently miss meals are more likely to overeat at other points in the day; therefore one of the key aspects of supporting weight management is to help the client to develop a structured eating pattern including regular meals. 25 The basis for these effects of starvation is both physical and psychological. Prolonged periods between meals result in depleted glycogen and blood glucose stores which may lead to cravings for food, particularly that which is energy dense.
Low calorie diets
Reducing calorie intake to lower than energy expenditure will inevitably result in weight loss. Emphasis has been placed on a 600-calorie deficit diet as an effective low calorie diet. This involves estimating an individual’s energy requirements and then subtracting 600-kcal. Formulas to estimate this have been published based on modified Schofield equations (Table 18.4). 26 And on a simplified predictive equation for resting energy expenditure proposed by Mifflin and St Jeor27:
| Age range | Male | Female |
|---|---|---|
| BMR equals | ||
| 10–17 years | 17.7 × weight (kg) + 657 | 13.4 × weight (kg) + 692 |
| 18–29 years | 15.1 × weight (kg) + 692 | 14.8 × weight (kg) + 487 |
| 31–59 years | 11.5 × weight (kg) + 873 | 8.3 × weight (kg) + 846 |
| 60+ years | 11.7 × weight (kg) + 587 | 9.1 × weight (kg) + 658 |
| Account for activity factor | ||
| Inactive | BMR × 1.4 | BMR × 1.4 |
| Light | BMR × 1.5 | BMR × 1.5 |
| Moderate | BMR × 1.78 | BMR × 1.64 |
| Heavy | BMR × 2.1 | BMR × 1.82 |
A review of 13 randomised controlled trials (RCTs) using 600-calorie deficit diets have demonstrated that this is an effective method of weight loss for some, resulting in an average weight loss of 5.32 kg after 12 months, compared to usual care. 28 This is the energy deficit that clients are most likely to be able to adhere to over the time required to achieve weight loss; greater deficits increase the risk of non-compliance. 29,30 This approach, however, will not suit everyone as it does require clients to plan meals and measure their intake.
The dietary assessment will support the dietitian to determine which clients are likely to benefit from this approach. These diets are generally based on the healthy eating principles. The use of low energy density foods, i.e. those with a high volume to calorie ratio, may support clients to follow an energy-deficit diet. This is based on the principle that the volume of food consumed rather than the calorie content influences satiety. 31,32
Low fat diets
Low fat diets have been encouraged both to support weight loss and to improve cardiovascular risk. Fat is more energy dense than other macronutrients and therefore reducing the proportion of fat in the diet can be a successful way of reducing the total calorie content. A meta-analysis of 16 trials has reviewed the effectiveness of low fat diets eaten ad libitum to achieve weight loss. 33 This analysis found that low fat diets resulted in an average weight loss of 3.2 kg lower than that of controls. There is, however, a paucity of research examining the efficacy of low fat diets on weight loss as many studies have not investigated weight change as a primary outcome.
Meal replacements
Meal replacements are generally considered to be ‘portion controlled products that are vitamin and mineral fortified and replace one or two meals in the day allowing one low calorie meal using standard foods (and snack/s)’. 34
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