Depression and weight – is there a link?

Depression and body weight have a tangled and interconnected relationship. Sarah Harrop takes a closer look.

Obesity and depression

It’s well known that we are in the middle of an obesity epidemic; in fact, worldwide obesity prevalence has almost tripled since 1975. According to World Health Organization figures, in 2016, more than 1.9 billion adults were overweight (defined as having a Body Mass Index (BMI) of 25 or more). Among these are over 650 million obese adults. It’s a major public health issue with most of the world’s population now living in countries where more people die from being overweight or obese than from being underweight.

Depression (or major depressive disorder) – which is defined as having a depressed mood or loss of pleasure or interest in activities for long periods of time – is also common, with an estimated 5% of adults globally affected by the condition.

Obesity and depression are close bedfellows, linked in a ‘chicken and egg’ style relationship, in which people with obesity are at a higher risk of depression, and those who are depressed are at increased risk of becoming obese. It’s a complex picture, but some of the predictors linking these two conditions are known to include:

• Financial insecurity or having trauma or troubles as a young person – Long-term stress from circumstances like these can raise levels of the stress hormone, cortisol, ultimately leading to higher insulin levels that drive down blood sugar, and causing cravings for sugary and fatty foods and therefore weight gain.
• The environment a person lives in – Those who live in ‘food swamps’ surrounded by fast food joints and convenience stores but far from shops selling fresh fruit and vegetables will face an uphill struggle to eat healthily, resulting in poor quality of life and poorer health.
• Anhedonia, the loss of interest and pleasure in activities – A common symptom of depression. When people suffering from anhedonia, they fail to get the ‘reward’ of satisfaction and pleasure that they used to get from eating, which can lead them to over-eat to try and make up for this absence.
• Impulse control: research has shown that people who are depressed are more likely to take risks than the general population. Similar cognitive impairments can result in eating disorders such as binge-eating and bulimia.

“Depression and obesity are common conditions with major public health implications that tend to co-occur within individuals. The relationship between these conditions is bidirectional: the presence of one increases the risk for developing the other,” says a Nature paper authored by Brenda Penninx and Yuri Milaneschi.

The paper reports the results of a systematic review into whether depression and weight gain or loss may have a shared biological mechanism, including possible culprits such as genetics, alterations in systems involved in keeping the body in a steady state (known as homeostasis) – from immune and metabolic factors to alterations in brain circuitries.

What about depression and weight loss?

Every person has a unique set of genetics, circumstances, symptoms and experiences when it comes to depression, and for some individuals, the condition can actually have the opposite effect and lead to loss of body weight.

Here are some of the risk factors which link mental disorders like depression with losing weight:

Appetite loss: some people with major depression experience loss of appetite. One 2016 study from PubMed in the American Journal of Psychiatry showed that people with appetite loss seemed to show less activity in an area of the brain associated with interoception, a sense that helps you feel and understand bodily sensations like hunger and thirst.

Anxiety and stress: people who are under stress go into so-called “fight or flight” – a physiological mechanism designed to prepare your body for a perceived threat. Adrenaline and the stress hormone cortisol are released by the body to prepare it to fight or run, and simultaneously suppress hunger and appetite. Cortisol temporarily tells the cells of the body to slow down functions that aren’t needed in an emergency situation, such as digestion, reproductive responses and the immune system. All of this can lead to weight loss – although prolonged release of cortisol can have the opposite effect, as described above.

Losing interest in eating: The feelings of hopelessness, sadness without a clear cause, and numb disinterest in everything which are the hallmarks of depression can fully occupy a person’s mental energy, squeezing out their ability to focus on daily activities such as dressing, washing or even preparing and eating meals – with weight loss as a knock-on effect.  

Antidepressant side-effects: While most antidepressants tend to cause weight gain, certain medications such as bupropion may cause weight loss during the first few months of use. Other research studies has shown that longer-term use (two years) of so-called second generation classes of antidepressant drugs known as selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), and selective serotonin norepinephrine reuptake inhibitors (SSNRIs) is significantly associated with long-term weight loss.

Cognitive distortions: In rare cases, people with severe depression can have thoughts that change their world view in a way that leads to weight changes, such as deliberately avoiding food because they feel they don’t deserve to eat, according to Johns Hopkins University psychiatrist Elizabeth Prince.

Conversely, some people experience feelings of depression after intentionally losing weight through dieting in an attempt to improve their body image and self-esteem. Being skinny makes you happy, or so the media and adverts would have us believe. So when becoming thinner through weight management doesn’t turn them into someone different, people can feel let down or even depressed when the reality of being slim doesn’t match what they had imagined.

So does depression cause weight loss or weight gain? It turns out the answer is complex and tangled, and it can do either or both depending on the unique set of circumstances and the individual experiencing the depression. 

One thing is certain though: treatment for depression can lead to improvements in all of its symptoms, including fatigue, loss of appetite and weight loss or gain. There is plenty of evidence that physical activity can also help with depression, and along with dietary changes to achieve a healthier lifestyle, getting more exercise can also help people to reach a healthy weight.

Change people’s lives for the better

A career in mental health and psychological wellbeing can be hugely rewarding because you can make a tangible difference and change the future trajectory of people’s lives. The University of Wolverhampton’s MSc Psychology of Mental Health and Wellbeing is for people looking to launch a career in mental health and psychological wellbeing who are not necessarily from a mental health background.

This flexible, 100% online Master’s degree is accredited by the British Psychological Society (BPS) – a key marker of quality for employers and a launchpad to becoming a chartered psychologist after graduation. The course will enable you to apply specialist knowledge and skills in innovative and creative ways to address psychology and mental health issues.

You’ll develop the specialist knowledge and professional skills of mental health practitioners, from clinical and counselling psychology to psychology of learning and research methods and statistical analysis. Along the way you’ll explore relevant case studies across key areas including clinical psychology and mental health online. 

Find out more about MSc Psychology of Mental Health and Wellbeing.