As we mark World Obesity Day on 4 March, during the Covid-19 pandemic, the link between weight and mental health has never been more pressing. Food and mood have long gone hand in hand, or rather mind to mouth, but more so in the past year. During lockdowns many of us found comfort in baking, eating delicious food and trying new recipes. The converse was trying to balance the new working-at-home effects on our meal planning and food preparation.
The results of our changing patterns in eating, however, don’t look good. A less than optimal diet obviously affected our health and also added to the global obesity crisis. Today, the prevalence of people who are overweight and obese is at an all-time high and it is increasing across the globe.
Globally more than 2.1-billion people (nearly 30% of the world’s population) are overweight or obese. If the current growth continues, some estimates predict 41% of the world’s population will be overweight or obese by 2030.
In South Africa, 68% of women and 31% of men are overweight or obese and 13% of children are overweight — this is far higher than the worldwide figures. So, we are already on the back foot.
We know that obesity is mainly caused by increasingly poor diets and lack of physical activity (with psychological factors in certain cases contributing to these behaviours) driven by our changing environments.
Recent lockdowns and the need for social isolation, changes in eating and physical activity patterns and remote working have very likely exacerbated the situation.
The important part of the cycle, which often goes unmentioned, is that the quality of the diet people consume can also affect their mental health – poor dietary habits alone have been found to increase the risk of depression by 18%.
One in four people in the world has been diagnosed with a mental or neurological disorder and mental health is one of the top 10 conditions contributing to the burden of disease in South Africa, with 16.5% of the adult population having a mental health disorder, including depression. Mental health is becoming an increasing concern during the coronavirus pandemic.
The mechanisms through which diet affects mental health are not straightforward and are yet to be fully understood, but inflammation appears to be one of several pathways. Research has found associations between pro-inflammatory diets (those high in sweets and refined starches, high-fat products, red and processed meat) and a significantly increased risk of depression, particularly among overweight and obese individuals. Another possible link between diet and mental health lies in the gut microbiota, which is negatively affected by diets high in ultra-processed foods.
Data collected by the Vitality programme at Discovery Health further supports this association between food choices and mental wellbeing. When analysing member purchasing data, we found that those who bought higher amounts of unhealthy foods (high in salt and sugar) were 1.7 times more likely to report psychological distress when completing mental wellbeing assessments, compared to those who had a healthier shopping basket.
What can be done about the situation?
Whereas a poor diet increases the risk for depression, the opposite is true for positive dietary changes, which may also hold promise for helping relieve the symptoms of depression. Professor Felice Jacka, director of the Food and Mood Centre at Deakin University in Australia and president of the International Society for Nutritional Psychiatry Research says: “We have now started to examine in great detail the links between the quality of the diets people consume and mental wellbeing, in particular the presence of depression. A higher quality diet is associated with about 30% reduction in the risk for depression.” She adds that this evidence is relevant not only in adults but across the lifespan, meaning that even in young people, the quality of diet is very clearly linked to their mental health.
The SMILES trial, in which Jacka was extensively involved and which was the first study to test dietary improvement as a treatment for depression, found positive changes to mood when people with depression improved their diet to include fresh fruits, vegetables, whole grains, legumes, nuts, extra virgin olive oil, and fish (commonly referred to as the Mediterranean diet). But it also found the greatest effect on their depressive symptoms was when the change in diet was coupled with reducing their intake of junk or highly processed unhealthy foods. Those who improved their diet the most experienced the greatest benefits.
Cost savings are also relevant. Although a healthy diet has a substantial mental wellbeing benefit, it is also highly cost-effective in the long term because it addresses people’s overall health – including physical, gut, immune system and mental health – potentially reducing the need for treatment of conditions.
Many of the risk factors for both mental disorders and obesity, like family history, life stress or early life trauma, are not easy to change. So, knowing about the good effects of foods, which we can control, is very powerful.
As we continue to navigate the varying levels of life in a Covid-19 world, perhaps it is an opportune time to also rethink our routines and patterns of behaviour and find those that nourish us in all the right ways, in both mind and body.