By Elisa Daly
“Elisa is a current MSc student in Nutrition and Behaviour, having already gained a PG cert in the Neuroscience and Psychology of Mental Health at King’s College London. She is particularly interested in the bi-directional links between nutrition and the brain and is keen to contribute to and raise awareness of the research in this field. Her passion is to bring together nutrition and mental health knowledge with her training background to make an impact on mental health outcomes, particularly in young adults.”

Given that January has now passed, and we are well on our way to spring, how many of those diets have proven to be sustainable and what is the fallout on mental health?

According to the last health survey for England in 2021, estimated levels of ‘obesity’ were at 25.9% of the population and a further 37.9% were considered to be ‘overweight’. Given the increasing use of these terms and a rise in our national battle with weight gain, many people will have started January with a weight-loss goal or diet plan. Some of the latest research highlights a few of the difficulties in following these plans. It invites us to reflect on issues such as weight stigma, our food environment and how these are intricately linked with our mental health.

The impact of fat and sugar on the brain

Our food environment presents us with daily tempting ultra-processed options, cleverly marketed to us in a variety of ways, making weight gain very easy to come by. We already know that these foods, which are usually high in fat and sugar, can be hard to resist and recent research now gives us further evidence as to why.

McDougle et al. conducted research published on the 18th January 2024 which provides further insights into the mechanisms of gut-brain communication. The research, conducted in mice, shows how separate vagal nerve neurons located in the gut each activate dopamine release via distinct nigrostriatal circuits. Moreover, these circuits reinforcing fat and sugar consumption have a larger effect when combined, resulting in overeating. This highlights how we can become subject to cravings which happen below our conscious level. It also reinforces that, in our current environment, where ultra-processed food (typically higher in fat and sugar) is so readily available, we can be faced with a very difficult challenge and diet plans can be readily abandoned.

Dieting and the impact on our mental health

As overeating becomes incredibly easy, consequent increases in weight gain, alongside social pressure can cause many to consider dieting. Now, recent research has provided more evidence on the potentially negative consequences of dieting.

As found by a recent qualitative study (Romo et al. 2024), going on a diet can impact an individual’s long term mental wellbeing. Most participants were motivated to start a diet to conform to societal pressure or to combat weight stigma, rather than for health reasons. The findings showed that starting a diet with this motivation set the stage for a cycle of yo-yo dieting and highlighted the damaging effects on mental wellbeing, including feelings of shame and unhappiness, overall pre-occupation with weight and disordered eating.

Implications and action

So, what should we take away from these findings and what are the solutions?
January diets for non-health related reasons should be discouraged according to the research, avoiding the beginning of a potentially addictive cycle. For those who need to lose weight to improve their health, researchers also hope that research into how fat and sugar communicate with the brain is promising for the future of anti-obesity treatment.

There are some positive steps being made. It was recently announced that the Australian curriculum is being changed to educate children and young people in a more positive light about nutrition and the body, in a bid to combat diet culture and weight stigma. In the UK, to limit the popularity of ultra-processed food, some places (including Bristol, Transport for London and Brighton and Hove) are leading the way by restricting advertising of some ultra-processed foods. More solutions, particularly around awareness and education could help improve the nation’s relationship with food and limit those January diets, shifting towards more sustainable health-orientated goals.

The bi-directional influence of the brain and our food choices is clear, the food we eat can communicate with our brain and societal pressure can dictate how we eat and feel about food. This invites us to an increased understanding of how our diet, weight loss and mental health are so intricately linked.

References to research:
McDougle, M., de Araujo, A., Singh, A., Yang, M., Braga, I., Paille, V., Mendez-Hernandez, R., Vergara, M., Woodie, L. N., Gour, A., Sharma, A., Urs, N., Warren, B. and de Lartigue, G., 2024. Separate gut-brain circuits for fat and sugar reinforcement combine to promote overeating. Cell Metabolism, 36 (2), 393-407.e397.
Romo, L., Earl, S., Mueller, K. A. and Obiol, M., A Qualitative Model of Weight Cycling. Qualitative Health Research, 0 (0), 10497323231221666