Across the world over 300 million people suffer from depression and over 650 million are affected by obesity! We investigate whether weight gain leads to higher rates of depression or the other way around!
There are a variety of potential mechanisms that link weight gain and depression and our unique health history, genetic makeup and microbiome can mean one person’s cause of weight gain might be completely different to another. In fact, there are even some people who lose weight when depressed due to a ‘typical’ response being a loss of appetite. Those who do gain weight when depressed are often considered to have a certain ‘sub- type’ of depression (1).
Although there are many potential causes, let’s look at a few theories behind this pesky partnership in order to understand what might be happening.
Theory 1: Being depressed means you are more likely to comfort eat
I’m sure we have all been there at some point! You’re sad, you want to feel better, so you reach for that chocolate bar which gives you a lovely dopamine (reward hormone) hit. This same behaviour has been witnessed in depressed populations where eating in response to negative emotions was seen as the driver between depression and the increase in body max index (BMI) and waist circumference (2).
When we are stressed over a long period of time, we tend to have increased levels of the stress hormone cortisol. Increased levels of cortisol have been shown to increase our hunger levels.
Dealing with poor mental health is also likely to be very stressful for an individual. When we are stressed over a long period of time, we tend to have increased levels of the stress hormone cortisol. Increased levels of cortisol have been shown to increase our hunger levels and opt for more sugary or fatty foods (3) that explains the chocolate cravings then!
Theory 2: Depression can lead to behavioural habits that promote weight gain
Alongside craving more calorie dense foods, a majority of people who suffer with depression may also find themselves: becoming less active, having poor sleep hygiene and even drinking more alcohol, which are all factors that can contribute to weight gain. In fact, inadequate sleep can increase cortisol levels which we have already learnt can influence our food decisions and make it much harder to opt for healthier options.
Theory 3: Being termed ‘over-weight’ could impact mental wellbeing
On the flip side of the spectrum, it is also possible that within a culture that often focusses on the ‘thin ideal’, individuals who live in a larger body, or have put on weight (for whatever reason) can often be made to believe that this is some sort of ‘failure’. The fact that less than 20% of people who lose weight through a weight loss intervention are able to maintain the loss after a year (4) and that following low calorie diets can impact mental health, should start ringing some alarm bells (5). New approaches like ‘intuitive eating’ and ‘health at every size’ are leading the way at supporting mental wellbeing by reducing stigma related to weight as they focus on adopting healthy behaviours rather than the numbers on a scale.
Theory 4: Imbalances in your gut microbiome could be contributing to your depression and weight gain
The trillions of bacteria within our gut are vital for not only digestion and our immune system but they are also essential for our mental wellbeing; especially as over 90% of serotonin (our happy hormone) is created in the gut. It is therefore unsurprising that individuals with depression are generally found to have a less diverse range of bacteria in their gut.
Although this area of research is still pretty new, there are also some small studies that have shown that individuals with depression have higher numbers of a type of bacteria called ‘firmicutes’. Compared to other predominant bacteria, these firmicutes tend to absorb more energy (calories) from the food consumed which could explain why some people can eat more than others without similar weight gains. This could also help to explain the depression/ weight gain link.
As shown, there doesn’t seem to be a one size fits all reason for why people may gain weight when they are depressed. It is likely though, that with the numbers of depression cases rising worldwide, research will continue to try to establish what is exactly happening within our bodies and hopefully develop new ways to treat (and prevent!) any unwanted side effects.
In the meantime, however, trying to fill your diet with a range of colourful fruit and vegetables along with moving your body in a way that makes you feel good is a great starting point to any improvement in health. In addition to this, developing different ways of dealing with stress and emotions (away from just food) could not only support resilience but could also help to encourage a more diverse gut microbiome, leading to a healthier and happier body and mind.
1) Levitan et al., (2012). Obesity Comorbidity in Unipolar Major Depressive Disorder. The Journal of Clinical Psychiatry, 73(08), pp.1119-1124.
2) Konttinen et al., (2019). Depression, emotional eating and long-term weight changes: a population-based prospective study. International Journal of Behavioral Nutrition and Physical Activity, 16(1).
3) Gluck et al., (2004) Cortisol, Hunger, and desire to binge eat following a cold stress test in women with binge eating disorder. Psychosom Med.[66:87]6–81.
4) Jeffery, R., Epstein, L., Wilson, G., Drewnowski, A., Stunkard, A. and Wing, R., 2000. Long-term maintenance of weight loss: Current status. Health Psychology, 19(1, Suppl), pp.5-16.
5) Kalm, L. and Semba, R., 2005. They Starved So That Others Be Better Fed: Remembering Ancel Keys and the Minnesota Experiment. The Journal of Nutrition, 135(6), pp.1347-1352.
6) Jiang et al., (2015) Altered fecal microbiota composition in patients with major depressive disorder. Brain Behav Immun.[48:18]6–94