This is what a low-calorie diet does to your mental health

Study results, Depressive symptom findings, The importance of a healthy dietary pattern, Protein, vitamin and mineral deficiencies, 'Controlled clinical trials would give better data', 'Seriously limited'

A low-calorie diet could increase the risk of developing symptoms of depression a study has suggested, but the consensus remains that losing weight is better for your mental health. The new research, published in BMJ Nutrition Prevention & Health, has reopened the debate on what effect – if any – diet has on people’s mental health and wellbeing. For the study, researchers in Canada used data from 28,525 people who took part in the US National Health and Nutrition Examination Survey (NHANES) and also completed a health questionnaire relating to depressive symptoms, which gave them a score based on severity. Of the total, 14,329 were women and 14,196 were men. Thirty three per cent were overweight and 38 per cent obese. The majority of the group (87 per cent) said they were not on a specific diet, while 2,206 were restricting calories. A little under 8 per cent reported depressive symptoms. (Photo: Getty)

Study results

Study results, Depressive symptom findings, The importance of a healthy dietary pattern, Protein, vitamin and mineral deficiencies, 'Controlled clinical trials would give better data', 'Seriously limited'

For the study, researchers in Canada used data from 28,525 people who took part in the US National Health and Nutrition Examination Survey (NHANES) and also completed a health questionnaire relating to depressive symptoms, which gave them a score based on severity. Of the total, 14,329 were women and 14,196 were men. Thirty three per cent were overweight and 38 per cent obese. The majority of the group (87 per cent) said they were not on a specific diet, while 2,206 were restricting calories. A little under 8 per cent reported depressive symptoms. Some 859 were on a “nutrient-restrictive” diet, low in fat, sugar, salt, fibre or carbohydrate, and 631 were on diets tailored for the likes of diabetes. Researchers found low-calorie diets were more common among obese patients and those who were overweight. (Photo: Chris Radburn/PA)

Depressive symptom findings

Study results, Depressive symptom findings, The importance of a healthy dietary pattern, Protein, vitamin and mineral deficiencies, 'Controlled clinical trials would give better data', 'Seriously limited'

Questionnaire scores for depressive symptoms – such as a low mood, low energy and sleep disturbances – were higher among those restricting calories compared to those who reported not being on a diet at all. The scores were also higher among overweight people following low-calorie diets. And the effects of calorie restriction on mood were more pronounced in men and overweight people, researchers said. The findings contrast previous studies which claim low-calorie diets improve depressive symptoms. However, the Canadian researchers argue prior trials included tailored and balanced diet programmes that may not be the same as what people realistically follow in everyday life. (Photo: Getty)

The importance of a healthy dietary pattern

Study results, Depressive symptom findings, The importance of a healthy dietary pattern, Protein, vitamin and mineral deficiencies, 'Controlled clinical trials would give better data', 'Seriously limited'

They said: “Numerous studies have consistently focused on ‘healthy’ versus ‘unhealthy’ diets. They have shown that ‘healthy’ diets rich in minimally processed foods, fresh fruits and vegetables, whole grains, nuts, seeds, lean proteins and fish have been linked to a lower risk of depression. In contrast, an ‘unhealthy’ diet dominated by ultra-processed foods, refined carbohydrates, saturated fats, processed meats and sweets is associated with an increased risk of depressive symptoms. Therefore, individuals must adopt a perfectly healthy dietary pattern to reduce the risk of depressive symptoms. This dichotomy fails to capture the complexity of real-world eating habits.” (Photo: Mas Bro/Getty)

Protein, vitamin and mineral deficiencies

Study results, Depressive symptom findings, The importance of a healthy dietary pattern, Protein, vitamin and mineral deficiencies, 'Controlled clinical trials would give better data', 'Seriously limited'

Restricting calories can lead to deficiencies in protein, vitamins and minerals, researchers suggest, which puts the body under stress. The findings also contradict previous studies showing low-calorie diets improve depressive symptoms. Researchers highlight that these studies were controlled trials, with those taking part following carefully designed and balanced diets. The team said a focus on “idealised diets” can “overlook the diversity of dietary patterns”, adding: “In contrast, real-life calorie-restricted diets and obesity often result in nutritional deficiencies, particularly in protein, essential vitamins and minerals, and induce physiological stress, which can exacerbate depressive symptomatology, including cognitive-affective symptoms.” (Photo: Roberto Machado Noa/LightRocket via Getty)

'Controlled clinical trials would give better data'

Study results, Depressive symptom findings, The importance of a healthy dietary pattern, Protein, vitamin and mineral deficiencies, 'Controlled clinical trials would give better data', 'Seriously limited'

Susan Jebb, professor of diet and population health at the University of Oxford said as an observational study the apparent association between reported ‘calorie-restricted’ diets and symptoms of depression is “at high risk of confounding from other factors”. She said: “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. 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 may be 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.” (Photo: Justin Lambert/Getty)

'Seriously limited'

Study results, Depressive symptom findings, The importance of a healthy dietary pattern, Protein, vitamin and mineral deficiencies, 'Controlled clinical trials would give better data', 'Seriously limited'

Naveed Sattar, professor of cardiometabolic medicine at the University of Glasgow, called the study “seriously limited” and pointed out trials using low-calorie diets in people with type 2 diabetes showed their quality of life “improved significantly compared to no intervention”. (Photo: Martin-dm/Getty)

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