The findings indicate that changes in food reward perception associated with depression do not occur across the board, but rather are specific to certain types of macronutrients. This supports the idea that depression may be linked to dysfunctional signaling between the gut and the brain.
Major depressive disorder (MDD) is a condition that affects millions of people worldwide, bringing symptoms such as persistent sadness, lack of interest in previously pleasurable activities, and changes in appetite and body weight.
Some people with depression feel hungrier and gain weight, while others lose their appetite and lose weight. These variations may indicate different types of depression, as they affect the brain in different ways, especially in how it responds to food-related stimuli.
Many studies use food image response tests to better understand these differences. During these tests, participants are shown pictures of different types of food, and researchers analyze brain activity in response to these stimuli.
The images include foods with different calorie levels and nutritional compositions, such as those rich in carbohydrates, fats or proteins. Previous studies have shown that our brains react differently to different types of food and that this response may be linked to how much we are willing to pay for a tasty meal.
Our brains process the nutritional value of food surprisingly quickly. Some research suggests that it takes just 100 milliseconds for us to identify the energy density of a food.
This suggests that people with depression may have an alteration in the way their brains evaluate food, which may influence their eating habits and even their metabolism.
There is a relationship between the composition of food and the way the nervous system processes food rewards. Fats and carbohydrates activate different pathways in the brain and gut.
While fats are detected primarily by nerves in the stomach, carbohydrates are identified by sensors in the portal vein, a large blood vessel connected to the liver.
Proteins, on the other hand, appear to be processed by a different pathway that is not yet fully understood. These connections between the brain and the gut may be one of the factors that explain why some people with depression have changes in appetite and weight.
In addition, there is a link between depression and the body's energy metabolism. Studies show that people with depression may have altered lipid (fat) metabolism and that stimulating the vagus nerve, which connects the brain to the digestive system, may help alleviate depressive symptoms, including changes in appetite and pleasure from eating.
The study, conducted by researchers at the University of Bonn, Germany, involved 117 individuals, 54 of whom were diagnosed with major depressive disorder (MDD) and 63 healthy participants, who formed the control group (HCPs).
All participants performed a food-cue reactivity task, in which they evaluated 60 types of food and 20 non-food items, assigning ratings of desire (how much they wanted to consume the item) and liking (how tasty they found the item).
To better understand how depression might influence these assessments, they analyzed the relationship between the scores given by participants and the nutritional composition of foods, focusing on their macronutrients (carbohydrates, fats, and proteins).
The results showed that patients with major depressive disorder had significantly reduced desire for foods compared to the control group, but the perception of taste remained similar between the groups.
When they included macronutrient composition in the analysis models, the accuracy of the results increased substantially. They observed that, in relation to foods rich in carbohydrates, patients with major depressive disorder gave even lower liking and desire scores for foods rich in fat and protein.
In addition, their food preferences showed weaker correlations between the different types of macronutrients, suggesting possible changes in the way their brains process the relationship between food and reward.
In summary, our findings indicate that changes in food reward perception associated with depression are not generalized, but rather specific to certain types of macronutrients.
This supports the idea that depression may be linked to dysfunctional signaling between the gut and the brain. These results raise the possibility that interventions targeting the digestive system could help restore healthy patterns of response to foods high in fat and protein.
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Altered food liking in depression is driven by macronutrient composition.
Lilly Thurn, Corinna Schulz, Diba Borgmann, Johannes Klaus, Sabine Ellinger, Martin Walter and Nils B. Kroemer
Psychological Medicine. 2025;55:e20.
doi:10.1017/S0033291724003581
Abstract:
Major depressive disorder (MDD) is characterized by changes in appetite and body weight as well as blunted reward sensitivity (‘anhedonia’). However, it is not well understood which mechanisms are driving changes in reward sensitivity, specifically regarding food. Here, we used a sample of 117 participants (54 patients with MDD and 63 healthy control participants [HCPs]) who completed a food cue reactivity task with ratings of wanting and liking for 60 food and 20 non-food items. To evaluate which components of the food may contribute to altered ratings in depression, we tested for associations with macronutrients of the depicted items. In line with previous studies, we found reduced ratings of food wanting (p = .003) but not liking (p = .23) in patients with MDD compared to matched HCPs. Adding macronutrient composition to the models of wanting and liking substantially improved their fit (ps < .001). Compared to carbohydrate-rich foods, patients with MDD reported lower liking and wanting ratings for high-fat and high-protein foods. Moreover, patients with MDD showed weaker correlations in their preferences for carbohydrate- versus fat- or protein-rich foods (ps < .001), pointing to potential disturbances in metabolic signaling. To conclude, our results suggest that depression-related alterations in food reward ratings are more specific to the macronutrient composition of the food than previously anticipated, hinting at disturbances in gut–brain signaling. These findings raise the intriguing question of whether interventions targeting the gut could help normalize aberrant reward signals for foods rich in fat or protein.
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