Calorie counting is not a new thing, but today, more and more people are growing conscious of their calorie intake. No wonder low-calorie diets continue to dominate health trends. But is it beneficial for you? Cutting back on calories may seem the right step, especially if you have a certain fitness goal or are on a weight loss plan. However, a new study suggests that the low-calorie diet might be making you grumpy.A new study published in the journal BMJ Nutrition Prevention & Health looked at the link between low-calorie diets and depressive symptoms.Diet and depression
The researchers found that low-calorie diets are linked to heightened risk of depressive symptoms. They observed that men and the overweight are especially vulnerable to the effects of restrictive eating. The researchers explained that a ‘healthy’ diet rich in minimally processed foods, fresh fruits and vegetables, whole grains, nuts, seeds, lean proteins and fish, is generally associated with a lower risk of depression, however, an ‘unhealthy’ diet, dominated by ultra-processed foods, refined carbs, saturated fats, processed meats and sweets, is generally associated with a heightened risk. As people follow different types of diets for health or medical reasons, including those that restrict calories or particular nutrients, they wanted to understand whether these other dietary patterns might be associated with a risk of depressive symptoms. The study
To understand the mental health implications of specific diet types, the researchers analyzed data from 28,525 adults (14,329 women and 14,196 men) who participated in the US National Health and Nutrition Examination Survey (NHANES) between 2007 and 2018. Participants also completed the Patient Health Questionnaire-9 (PHQ-9), a tool used to measure the severity of depressive symptoms.The findings were shocking. 2508 people (just under 8%) reported depressive symptoms, and 7995 participants (29%) had a healthy weight; 9470 (33%) were overweight; and 11060 (38%) were obese. The participants were asked about their diet, and based on the dietary patterns, they were categorised into 4 groups: (1) calorie-restrictive; (2) nutrient-restrictive (low in fat/cholesterol, sugar, salt, fibre, or carbs); (3) established dietary patterns (adapted for diabetes, for example); and (4) not on a diet. Most participants (25,009, 87%) said they weren’t on any specific diet. 2026 (8%) of them followed a calorie-restrictive diet, 859 (3%) a nutrient-restrictive diet, and 631 (2%) an established dietary pattern. 90% of men and 85% of women said they weren’t on a diet. Calorie restriction was reported in obese participants (1247;12%) and those who were overweight (594; 8%). The researchers also noticed that nutrient-restrictive and established dietary patterns were less commonly reported, with the highest proportion of established dietary pattern users among obese participants (359; 3%).The study found that PHQ-9 scores, a measure of depressive symptom severity were 0.29 points higher among those on calorie-restrictive diets compared with those not following any specific diet. For overweight individuals following such diets, the increase was even greater: 0.46 points higher for calorie-restrictive diets and 0.61 points higher for nutrient-restrictive diets.They found that calorie-restrictive diets were linked to higher cognitive-affective symptom scores (measure of relationship between thoughts and feelings) while nutrient-restrictive diets were associated with higher somatic symptom scores (excessive distress and anxiety about physical symptoms).These scores also varied by gender. A nutrient-restrictive diet was associated with higher cognitive-affective symptom scores in men than in women not on a diet, while all 3 types of diet were associated with higher somatic symptom scores in men. Also, people with obesity following an established dietary pattern had higher cognitive-affective and somatic symptom scores than those of a healthy weight not on a diet.What are the experts saying
The findings contradict previous research that suggested low calorie diets improve depressive symptoms. “This discrepancy may arise because prior studies were primarily randomised controlled trials (RCTs) where participants adhered to carefully designed diets ensuring balanced nutrient intake. In contrast, 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 including cognitive-affective symptoms,” the researchers said. They also suggested that another possible explanation might be a failure to lose weight or weight cycling—losing weight and then putting it back on.“Diets low in carbohydrates (glucose) or fats (omega-3s) may theoretically worsen brain function and exacerbate cognitive-affective symptoms, especially in men with greater nutritional needs,” they added.Professor Sumantra Ray, Chief Scientist and Executive Director of the NNEdPro Global Institute for Food, Nutrition and Health, in a statementsaid, “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.”
“But the effect sizes are small, with further statistical limitations limiting the generalisability of the findings. Further well designed studies that accurately capture dietary intake and minimise the impact of chance and confounding are needed to continue this important line of inquiry,” Ray added.
