The relationship between mental health and obesity

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This month we spoke to Arti Dhokia, Advanced Mental Health and Gastroenterology Dietitian at Priory Hospital Woodbourne, about the relationship between mental health and obesity. Arti specialises in eating disorders, spotting the early signs of disordered eating, weight gain/loss management, and has a particular interest in obesity management.

We explore the links between ‘food and mood’, what the signs and symptoms of poor nutrition are and how it is linked to mental health recovery, the effects that mental health medication can have on weight, and what particular foods can help to improve wellbeing.

Why is this so important?

Despite there being a number of demographic variables that could affect the direction and/or strength of this link, including socioeconomic status, level of education, age, gender and ethnicity, a 2010 systematic review highlighted a two-way association between depression and obesity. The review found that people who were obese had a 55% increased risk of developing depression over time, whereas people experiencing depression had a 58% increased risk of becoming obese.

It is estimated that the NHS spent £6.1 billion on overweight and obesity-related ill-health from 2014 to 2015.  Failing to address the challenge posed by the obesity epidemic will place an even greater burden on NHS resources. This emphasises the importance of spotting the early signs of disordered eating as well as carefully considering the influence of mental health on obesity.

The relationship between mental health and obesity is complex

It has become increasingly clear that obesity may also be a side effect of medications used to manage mental health issues. Increased appetite or overwhelming lethargy can both contribute to undesired weight gain and the associated long-term consequences.

Moreover, the development of co-morbid conditions such as diabetes or joint pain can significantly reduce quality of life. As medication is often an essential element of treatment, diet and lifestyle changes should be first-line interventions for managing weight.

General healthy eating guidelines, although indispensable, may alone not be effective in precipitating change in this patient group. Additional education is often required, to enable patients to develop a greater understanding of the relationship between food and mood, in order to make small but meaningful changes.

For example, serotonin is made from the amino acid tryptophan, which is better absorbed with carbohydrate-rich foods, which goes some way to explain ‘carbohydrate cravings’ and the excessive consumption of sweet and comforting carbohydrate foods, to boost mood. However, evidence to show that an increase in carbohydrate consumption can improve mood in the long-term, is currently lacking. The short-term reward associated with these foods can contribute to excess weight gain, and consolidate habitual behaviours that patients may struggle to change if no intervention is offered.

Improvements in both dietary intake and one’s relationship with food will likely result in reduced weight gain and improved mental health, which in turn is likely to improve compliance with medication.

Signs and symptoms of poor nutrition, and how it is linked to mental health recovery

The association between poor nutrition and anxiety disorders is well documented and there are many signs and symptoms a GP can look out for when making as assessment as to whether a patient may have disordered eating:

  • Loose or tight clothes, belts, jewellery
  • Being tired and less energetic
  • Not being as capable at performing activities of daily living
  • Being less physically active e.g. not being able to walk as far or as quickly as before
  • Changes in mood, such as becoming depressed and lethargic
  • Getting ill often, and taking a long time to recover
  • Delayed wound healing
  • Poor concentration

It is important to remember that weight loss or weight gain can be due to many different reasons – weight monitoring in patients is very important, and unintended weight loss should be a red flag.

What can be done in a GP consultation?

  • Weight monitoring in patients taking mental health medication is essential – intervention should ideally begin as soon as weight increases are noted
  • Ask questions around changes in appetite
  • Have discussions around the relationship between food consumption and mood. This can help to start discussions around food choices and comfort eating
  • Attempt to gain input from family and carers, if they are attending the GP consultation with the patient. This is invaluable as it is well documented that patients ‘under-report’, when asked what they are eating

Educating patients on good nutrition and mental wellbeing

Diet is a low risk, cost-effective and modifiable risk factor when considering mental health recovery. GPs should be encouraged and supported to test people for nutritional deficiencies if they suspect that their mental health problems could be linked to poor diet, and to prescribe supplements if there is a deficiency.


The ability to concentrate comes from the adequate supply of energy to the brain; up to 25% of our total glucose intake is used by the brain. It is thought that a low carbohydrate diet can lead to low mood. With the rise in popularity of ketogenic diets (high protein/high fat), it is important that patients suffering or recovering from mental health issues are aware of the role of carbohydrates in brain function and absorption of tryptophan for serotonin production.

These patients may be particularly susceptible to the enticement of fad dieting, as they may have gained weight from mental health medication and have reduced self-esteem as a result.


Low levels of iron and the resulting reduction in oxyhaemoglobin can lead to patients feeling tired, weak and lethargic. This is likely to significantly impact on an individual’s self-efficacy and mood. The risk of anaemia is reduced with adequate intakes of iron, particularly from red meat, poultry and fish. Vegetarian sources are found in beans, pulses and fortified breakfast cereals.

It may be helpful to ask about an anaemic patient’s consumption of tea, as tannin in tea reduces iron absorption. Avoiding tea with meals can be helpful, and drinking orange juice with iron containing foods even more so, as this will help to increase absorption.

B vitamins

Deficiencies in B vitamins can increase the feeling of tiredness, and cause patients to feel depressed and irritable. Fortified foods include wholegrain cereals and animal protein foods such as meat, fish, eggs and dairy.

B vitamin deficiency is common amongst vegans. The Vegan Society states that the ‘Veganuary’ campaign, where people eat vegan for the month of January, grew by 183% in 2018, with a whopping 168,500 participants. With veganism becoming a rising trend, it is imperative that the risk of B vitamin deficiency and supplementation is discussed for those with at risk or with a history of mental health disorders.

IBS, probiotics and FODMAP

Irritable bowel syndrome (IBS) is associated with higher levels of mood disorders, anxiety, and other psychiatric conditions. IBS reportedly affects up to 23% of people around the world, and although IBS is not fully understood, symptoms appear to result from a disturbance in the brain-gut axis—the line of communication that exists between the brain and the gastrointestinal tract—and may be underpinned by disruptions in the microbiome-immune interface.

The current state of the gut microbiome can be preserved by improving dietary fibre and diversity of foods to promote microbial diversity.

The gold standard for IBS management is the Low FODMAP diet for IBS, which reduces fermentation in the bowel, and allows the gut respite from ongoing fermentation by omitting long chain carbohydrates from the diet, delivered under the supervision of a specialist dietitian. With a 71% success rate of satisfactory symptom reduction at one year (as reported by Kings College London), the FODMAP diet has provided a much needed framework for IBS treatment in primary care.

The influence of cognitive behavioural therapy (CBT)

Dietary management of IBS can improve symptoms significantly, however this is most effective when placed alongside psychological therapies such as CBT. This treatment allows the patient to understand root causes of disordered eating and teaches them how to cope better with anxiety and depression, which may lead to over-eating.

The British Society of Gastroenterology recommends psychological therapy alongside FODMAP diet as first-line treatment when the patient has a history of anxiety, panic attacks, or depression.

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