Eating less of a bad diet is not going to boost your mental health unless you change what you eat, research suggests after a study showed men are vulnerable to negative impact of ‘restrictive eating’
Counting calories and yo-yo dieting could increase your risk of depression, new research suggests.
Experts say eating healthy whole foods rather than processed foods might be more important than focusing only on cutting down on calories. The study of 28,500 Americans suggests men are particularly “vulnerable” to the negative effects of “restrictive eating” due to a lack of essential nutrients. The findings, published in BMJ Nutrition Prevention and Health, contradict previous studies which found low-calorie diets improved depressive symptoms. However researchers said earlier controlled trials included tailored and balanced diet programmes that may not be the same as the calorie counting diets people realistically follow in everyday life which contain the same processed foods.
Study author Dr Venkat Bhat, of the University of Toronto, Canada, said worsening depressive symptoms could be caused by a failure to lose weight or “weight cycling” – losing weight and then putting it back on. He said: “Real-life calorie-restricted diets and obesity often result in nutritional deficiencies – particularly in protein, essential vitamins/minerals – and induce physiological stress, which can exacerbate depressive symptomatology.”
Canadian researchers analysed data on 28,525 people who took part in the US National Health and Nutrition Examination Survey (NHANES) and had completed a health questionnaire relating to depressive symptoms, which gave them a score based on severity.
Some 8% of those studied had reported depressive symptoms, while 33% were overweight and 38% were obese. Most said they were not on a specific diet, while 2,206 were restricting calories. 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.
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 research paper concluded: “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.”
Researchers said restricting calories can lead to deficiencies in protein, vitamins and minerals which puts the body under stress.
Professor Sumantra Ray, chief scientist and executive director of the NNEdPro Global Institute for Food, Nutrition and Health, which co-owns the BMJ medical journals, said: “This study adds to the emerging evidence linking dietary patterns and mental health, raising important questions about whether restrictive diets which are low in nutrients considered beneficial for cognitive health, such as omega-3 fatty acids and vitamin B12, may precipitate depressive symptoms.
Scientists explained that a “healthy” diet rich in fresh fruits and vegetables, whole grains, nuts, seeds, lean proteins and fish, is generally associated with a lower risk of depression. An “unhealthy diet” – dominated by ultra-processed foods, refined carbs, saturated fats, processed meats and sweets – has been linked to a heightened risk.
Prof David Curtis, honorary professor at University College London, wo was not involved in the research, said: “The reported effects are small and some are scarcely statistically significant, so may well be due to chance. Even if it is the case that people who are dieting have more depressive symptoms, I don’t see why we should assume that it is the dieting which causes this.
“To me it seems plausible that this observation could be accounted for by the fact that people who are more unhappy with themselves, and with their weight in particular, may be more likely to go on a diet in an attempt to change their situation.”