Depression and Obesity
Depression is prevalent throughout society, but the condition is particularly common in obese individuals. A positive relationship exists between depression and BMI, and obesity has been found to be predictive of subsequent depression. What links the two is not fully understood, but research to date has suggested several possible causal pathways.
Previously referred to as ‘melancholia’, a term first applied by the ancient Greeks and in regular usage until the 20th century, depression has long been acknowledged as a common problem, although treatment options and attitudes towards the illness have changed over time.
Several theories exist as to why depression occurs, with psychological, physiological, social and genetic factors all thought to contribute. Illness, injury or a stressful life event may precipitate a bout of depression, and individuals with personality traits such as low self-esteem, poor self-image or a tendency towards pessimism or self-recrimination are particularly vulnerable to the condition. The presence of diabetes, cardiovascular disease, eating disorders and obesity are also considered risk factors for depression.
What Does a Diagnosis of Depression Mean?
Whilst depression may be classified as mild, moderate or severe, depressive symptoms exist upon a continuum and can vary greatly between individuals. Fatigue or low energy, impaired concentration, feelings of worthlessness, excessive or inappropriate guilt, sleep disturbances, recurrent thoughts of suicide or self-harm, changes in appetite and increased or decreased physical and mental activity can all be symptomatic of the condition, but for a clinical diagnosis of depression to be reached, the core symptoms of low mood and loss of interest in everyday activities must be present on most days for a minimum period of two weeks, in the absence of an external source of stress such as bereavement or other major life event. (Depressive symptoms can frequently manifest following such events and are only considered pathological if they persist for a prolonged period of time).
In modern healthcare settings depression is usually defined in accordance with one of two systems of classification: the tenth revision of the International Classification of Diseases (ICD-10), or the fourth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). There are currently no laboratory tests for depression, so diagnosis is based upon clinical interview, sometimes in conjunction with a self-report questionnaire or rating scale, such as the Patient Health Questionnaire (PHQ-9) or Beck Depression Inventory. Laboratory tests or imaging studies may be performed to rule out differential diagnoses such as hypothyroidism, drug side effects or intracranial lesions and it is possible for the condition to present solely with somatic symptoms, including headaches, back pain, musculoskeletal pain, dizziness or feeling lightheaded, back pain, chest pain, digestive disorders and abdominal discomfort, which may warrant further investigation to exclude physical illness.
Functional Impairment and Quality of Life
Functional impairment is strongly associated with depression and obese individuals frequently experience impaired physical function and reduced quality of life. Carrying excess weight can make it more difficult to perform basic day to day activities, with those with the highest BMI typically experiencing greatest difficulty. Lack of physical exercise is common amongst obese individuals, and is positively associated with depression. Obese individuals are also subject to elevated rates of chronic disease, which can directly and indirectly impact upon functional ability and quality of life. Diabetes in particular is frequently associated with obesity and also a known risk factor for depression.
Obese individuals can experience poorer self-perception of health and ability, possibly occurring as a result of media attention given to the health risks associated with obesity. In other words, an obese individual may perceive themselves to be less healthy or able than is actually the case. This form of negative self-perception is itself associated with depression.
Obesity Prejudice, Self Esteem and Stress
Exposure to prejudice can lead to poor self-image, low self-esteem and depression, particularly in individuals with high self-acceptance of negative stereotyping. Weight-related prejudice is known to increase in line with BMI, with the heaviest individuals subject to the highest levels of social stigma and obese women in particular being more likely to be dissatisfied with their body shape and have poorer body image than the general population. Strong social networks and supportive relationships can be protective against stress and depression, but prejudice can often precipitate social isolation, rejection and loneliness.
Various studies have independently linked stress to depression and obesity, with many obese individuals citing stress as a factor in their lack of ability to maintain a healthy weight over time. Stress has been positively associated with visceral adiposity and there is evidence to suggest that reducing stress can lead to a reduction in depressive symptoms.
The complex associations between stress, depression and obesity are not fully understood, but stress is known to trigger unhealthy behaviors such as increased alcohol consumption, increased preference for foods high in sugar or fat, disordered eating, lack of regular exercise and altered sleep patterns, all of which can lead to weight gain as well as increased susceptibility to depression. Discrimination, whether actual or perceived, can also be a source of stress.
Depression with Weight Loss Attempts
Several studies have reported a relationship between repeated or “yo-yo” dieting and depression. An unsuccessful attempt to control weight by dieting, or regain of weight following a diet can foster a sense of failure, leading to low mood. There is also some evidence to suggest that being on a diet can itself lead to low mood. Research has shown a higher BMI to be associated with more dieting attempts. Hence an individual with a particularly high BMI is likely to have unsuccessfully dieted many times, and may thus be more prone to low mood as a result.
Depression has also been shown to predict attrition from weight-loss programs, suggesting that depression can directly hinder weight loss attempts. This may occur because it is more challenging to engage in activities such as meal-planning or participation in regular exercise in the presence of depression. There is also some evidence that expected weight loss is predictive of actual weight loss. Hence the pessimism typically observed in depressed individuals may inadvertently cause them to adopt the self-fulfilling view that their weight loss attempt will fail.
Physiological Factors that Relate Obesity and Depression
There is evidence to suggest bidirectional causality between depression and obesity with depressed individuals at increased risk for becoming obese. Several possible mediating factors have been identified, including HPA axis dysregulation and inflammation.
The hypothalamus, pituitary gland and adrenal glands are hormone-producing organs that work together to form what is known as the hypothalamic-pituitary-adrenal (HPA) axis; an important part of the neuroendocrine system responsible for regulating many physiological processes including digestion, the stress response, reproductive function and fat metabolism, as well as mood and emotion. Dysregulation of the HPA axis is difficult to assess clinically, but is known to be associated with stress and depression, and has also been linked to sleep deprivation, disordered eating and visceral adiposity. Weight gain activates inflammatory pathways such that obesity is classed as a chronic inflammatory state and inflammation is a known risk factor for depression. There also is some evidence to suggest that chronic inflammation can itself lead to HPA axis alterations.
Bariatric Procedures as Treatment for Depression
Current evidence is supportive of bariatric procedures having a beneficial effect upon depression. Bariatric surgery is associated with improvements in several health conditions linked to depression, including diabetes and cardiovascular disease, and weight loss can facilitate significant improvements in quality of life, physical function and self-esteem, yet whilst some studies have reported direct correlation between postsurgical weight loss and reduction in depressive symptoms, there is also evidence to suggest that bariatric procedures can ameliorate depression independently of weight loss. It has been hypothesized that such improvements may occur as a result of the increased access to support and weight loss counseling that accompanies active participation in effective bariatric programs. It is important that weight-loss interventions for obese individuals who are depressed take both factors into account.
Many different treatment options for depression exist, with the most appropriate choice of treatment depending on various factors including degree and duration of depression as well as overall state of physical and mental wellbeing.
Exercise Can Help Depression
The neuroendocrine effects of exercise closely resemble those of some anti-depression medications, and whilst exercise alone is not generally sufficient to resolve depression or obesity, it is known to have a beneficial effect upon mood and stress levels, as well as promoting weight loss. Initial negative experiences of exercise are strongly predictive of overall failure to adhere to an exercise regime, so it is generally preferable to choose an enjoyable activity or try to incorporate small amounts of exercise into an existing schedule rather than begin with a difficult or inconvenient form of exercise.
Several different forms of psychotherapy or talking therapy are considered highly effective in the treatment of depression, with Cognitive Behavioral Therapy (CBT) being particularly well validated. CBT can also help tackle unhealthy behaviors associated with food and eating and facilitate development of skills such as time management and forward planning that are important in managing stress and maintaining a healthy lifestyle. According to the CBT model, actions, thoughts, emotions and physical sensations are all interconnected, such that any factor impacting upon one area can affect other areas too, potentially triggering a cyclic cascade of negative consequences. CBT provides a practical framework in which to explore and challenge the negative thoughts, beliefs and attitudes that can contribute towards low mood.
Antidepressant drugs may be prescribed alone or in combination with psychotherapy. The most commonly prescribed forms of antidepressant act upon chemical messengers or neurotransmitters in the brain such as serotonin or norepinephrine, which are known to affect mood and emotional response. However, the exact mechanisms underlying the effects of these drugs remain unclear.
Antidepressants can help to reduce depressive symptoms relatively quickly in responsive individuals, with typical onset of action occurring within two to six weeks of treatment. However, recent research suggests that antidepressants may not be effective for mild to moderate cases of depression, and side effects such as weight gain, digestive disturbances, dry mouth, insomnia, erectile dysfunction and hyperhidrosis can occur. Additionally, antidepressant drugs treat the symptoms rather than the underlying causes of depression so relapses are common on cessation of treatment.