A randomized clinical trial in Iran exploring the effects of a low-calorie, high-protein diet on obese individuals found that 15 days on this diet resulted in decreased symptoms of anxiety and depression. After 30 and 60 days, participants adhering to this diet also reported lower stress scores. The research was published in Nutritional Neuroscience.
Obesity is a medical condition characterized by excessive body fat accumulation that may impair health. It is typically measured using the body mass index (BMI), where individuals with a BMI of 30 or higher are classified as obese. BMI is calculated as one’s weight in kilograms divided by the square of their height in meters. Obesity increases the risk of numerous health issues, including diabetes, heart disease, certain cancers, and joint problems.
While people often attribute the development of obesity to poor dietary choices, scientific studies suggest a more complex picture. Obesity appears to result from a combination of lifestyle, environmental, and genetic factors, leading to a dysregulation of the brain’s food intake regulation system. This makes it difficult for obese individuals to reduce their food intake or regulate it effectively to prevent weight gain. For instance, studies have shown that, unlike individuals of normal weight, the brains of obese individuals expend extra energy when resisting food cravings. Additionally, chronic consumption of foods rich in easily digestible fats and sugars disrupts the brain’s food intake regulation mechanisms, contributing to obesity. Diets high in these components are often referred to as obesogenic diets.
Over the past several decades, obesity has become a global epidemic, with many countries and regions reporting that a majority of their populations are overweight or obese. This has spurred scientists to intensively search for ways to reverse obesity or alleviate its adverse consequences.
Study author Fatemeh Sadat Hashemi Javaheria and her colleagues sought to explore the effects of a low-calorie, high-protein diet on depression in obese individuals. Previous research has reported that low-calorie diets can mitigate depression in obese individuals, while high-calorie diets are associated with an increased risk of depression. Additionally, high protein intake has been shown to improve cholesterol and triglyceride levels, which may also contribute to reducing depression.
The study included 60 obese individuals with no other health issues. Their average age was 33 years, and 31 participants were women. The participants’ average weight was 99 kilograms.
Participants were randomly assigned to either the intervention group or the control group. Those in the intervention group followed a low-calorie diet with increased protein content for 60 days. In contrast, participants in the control group followed a diet with standard protein levels for the same period.
Since all participants were obese, the diets for both groups included a daily caloric deficit of 750 kcal to facilitate weight loss. In the intervention group, 30% of the diet consisted of protein, compared to 12% in the control group.
Participants’ mental health was evaluated using the DASS-21 scale, which assesses symptoms of anxiety, stress, and depression, at several points throughout the study. Researchers also recorded participants’ body measurements.
The results showed that after 15 days of intervention, participants in the high-protein group reported lower symptoms of depression and anxiety compared to the control group. After 30 days, they also reported lower stress levels.
“The results of this study showed that when controlling for the effect of confounding variables such as physical activity, low-calorie diets with a high-protein percentage can significantly improve psychometric variables in obese individuals,” the study authors concluded.
The study contributes to the scientific understanding of the potential effects of low-calorie, high-protein diets on mental health symptoms in obese individuals. However, the reported DASS-21 scores indicate that, on average, participants did not exhibit elevated symptoms of depression, anxiety, or stress at the start of the study.
Additionally, as this was an open-label study, participants were aware of their assigned groups, which may have influenced their behavior or responses. This awareness raises the possibility of the Hawthorne effect, where individuals modify their behavior or self-reported outcomes simply because they know they are being observed. Combined with the transparency of the DASS-21, a self-report measure where it is evident which responses indicate more favorable outcomes, there is potential for reporting bias or the Hawthorne effect to impact the results.
The paper, “The effect of a low-calorie, high-protein diet on psychometric variables in obese individuals: a Randomized Clinical Trial,” was authored by Fatemeh Sadat Hashemi Javaheria , Alireza Ostadrahimi, Mohsen Nematy, Seyyed Mostafa Arabi, Kazem Rahmani, and Mahnaz Amini.
