June 3, 2025

expert reaction to observational study on low calorie diets and depressive symptoms

An observational study published in BMJ Nutrition, Prevention & Health looks at the mental health consequences of low calorie diets.

Prof Stella Chan, Charlie Waller Chair in Evidence-based Psychological Treatment, University of Reading, said:

“This research study contributed to the emerging field of nutritional psychiatry by showing a potential link between dietary habits and mental health in US adults. The study also provided further observations around individual differences by gender and BMI status. However, these findings must be treated with caution because of methodological limitations. Cross-sectional findings can only show an association but cannot identify causal directions. Depressed individuals could be more prone to following a restrictive diet, or that diets and mental health have no direct association but are underpinned by common risk factors. These findings can also only generalised to mainstream U.S. populations, biasing towards those who were able and willing to complete relevant measures. Future research should widen relevant mental health outcomes, such as disordered eating and anxiety which often co-occur with depression, and to use more robust measures than self-reported self-identified measures on dietary habits.”

Prof Susan Jebb, Professor of Diet and Population Health, University of Oxford:

“This is an observational study and so the apparent association between reported ‘calorie-restricted’ diets and symptoms of depression is at high risk of confounding from other factors. Higher quality data comes from controlled clinical trials where the consensus of evidence is that weight-loss interventions lead to small improvements in symptoms of depression (e.g. https://pmc.ncbi.nlm.nih.gov/articles/PMC7116866/, and https://pubmed.ncbi.nlm.nih.gov/38084632/).

“It is possible that the benefits of weight loss observed during a trial may also relate to the structured support offered to participants and it maybe that people trying to lose weight alone, without support may experience poorer mental health.  This has not been specifically demonstrated, but if true, it would reinforce the importance of providing access to structured and supportive programmes for people living with obesity and who want to lose weight to improve their health.”

Prof Naveed Sattar, Professor of Cardiometabolic Medicine/Honorary Consultant, University of Glasgow, said:

“This study is seriously limited as cross-sectional so cannot determine cause and effect, and reverse causality may play a role whereby people having to consider such diets may be doing so for other reasons in their lives that leads them to gain weight.  In low calorie diet randomised trial in people with type 2 diabetes, quality of life improved significantly compared to no intervention (https://pubmed.ncbi.nlm.nih.gov/29221645/) whereas the same low calorie intervention in people living with Long COVID, did not observe any adverse impact on depressive symptoms, but rather a potential benefit in the hospital anxiety and depression scale (HADS) score at 6 months (https://pubmed.ncbi.nlm.nih.gov/39779922/).”

‘Mental health consequences of dietary restriction: increased depressive symptoms in biological men and populations with elevated BMI’ by Gabriella Menniti et al. will be published in BMJ Nutrition, Prevention & Health at 23:30 UK time on Tuesday 3 June, which is when the embargo will lift.

DOI: 10.1136/ bmjnph-2025-001167

Declared interests

Prof Susan Jebb:

1. The Food Standards Agency is a non-ministerial government department set up in 2000 to represent consumer interests in relation to food;
2. The Chair, Professor Susan Jebb is also Professor of Diet and Population Health at the University of Oxford, a member of the Public Health England Obesity Programme Board and Chair of the DH Public Health Responsibility Food Network;
3. Here’s a link to her register of interests from the FSA website : https://www.food.gov.uk/about-us/professor-susan-jebb-obe-phd-frcp-hon-fmedsci-fsa-chair

Prof Naveed Sattar: “NS has consulted for and/or received speaker honoraria from Abbott Laboratories, AbbVie, Afimmune, Amgen, AstraZeneca, Boehringer Ingelheim, Carmot Therapeutics, Eli Lilly, GlaxoSmithKline, Hanmi Pharmaceuticals, Janssen, Menarini-Ricerche, Merck Sharp & Dohme, Metsera, Novartis, Novo Nordisk, Pfizer, Sanofi, and Roche; and received grant support paid to his University from AstraZeneca, Boehringer Ingelheim, Novartis, and Roche. No shares in any medical areas.”

For all other experts, no reply to our request for DOIs was received.