A study of obese rats in Brazil found that adding extra virgin olive oil to their diets reduced inflammation in the arcuate nucleus of the hypothalamus, prevented them from gaining excessive weight, and improved a number of metabolic parameters. The research was published in Nutritional Neuroscience.

Extra virgin olive oil is the highest-quality form of olive oil, obtained directly from olives using only mechanical methods without any chemical refining. It must meet strict standards for acidity (less than 0.8%) and pass sensory tests for taste and aroma. Extra virgin olive oil retains the natural flavors and antioxidants of the olive fruit because it is cold-pressed and minimally processed.

Regular olive oil, in contrast, is usually a blend of refined olive oils and some virgin oil to improve flavor. Refining removes impurities but also strips away many beneficial compounds, making it milder in taste and lower in nutrients.

Extra virgin olive oil has a distinct fruity, peppery, or slightly bitter taste depending on the olive variety and ripeness. It is rich in heart-healthy monounsaturated fats, and its minimal processing preserves high levels of polyphenols and vitamin E, which have antioxidant and anti-inflammatory properties. Regular olive oil is lighter in flavor, more stable at high temperatures, and often used for frying or cooking in bulk. Extra virgin olive oil, however, is a better choice for salads, drizzling, and dishes where its aroma can be appreciated.

Study author Ariadni Peres and her colleagues wanted to explore whether extra virgin olive oil can be used to treat obesity. More specifically, they wanted to explore the effects of EVOO supplementation on various metabolic parameters, satiety, and hypothalamic inflammation—all hallmarks of diet-induced obesity.

These authors conducted a study on 21-day-old Wistar rats. Wistar rats are a common albino laboratory rat strain widely used in biomedical research because of their calm temperament and well-documented physiology. They were kept in cages with up to 4 same-sex animals per cage.

The rats were divided into 4 groups. The first group received regular rat food (standard chow). The second group received the same type of regular food, but also EVOO supplementation. The third group was on a high-fat diet (HFD), eating food with an increased content of fats. Finally, the fourth group received the high-fat diet and extra virgin olive oil supplementation. Olive oil supplementation was administered daily by gavage.

The standard chow was composed of 11.9% fat, 58.8% carbohydrate, and 29.2% protein, with an energy density of 3.86 Kcal/g. In contrast, the high-fat diet contained 64% of its calories from fat. Extra virgin olive oil supplementation was 1.3 mL/Kg body weight.

The rats were kept on this diet throughout the study. On day 61 of their lives, study authors took the rats’ blood samples to determine their fasting glucose levels. On days 63-65 the rats completed a number of behavioral satiety tests. On day 70, the rats were euthanized, allowing researchers to analyze their tissues and conduct various biochemical analyses.

Results showed that, as expected, rats fed the high-fat diet became obese. However, extra virgin olive oil supplementation prevented the excessive weight-gain caused by the high-fat diet. It also reduced the level of inflammation in the arcuate nucleus of the hypothalamus and improved a number of other metabolic parameters in rats fed a high-fat diet.

“Our results demonstrate that extra virgin olive oil supplementation seemed promising, improving hypothalamic inflammation in obese animals, [and] therefore might lead to the restoration of adverse metabolic consequences,” the study authors concluded.

The study sheds light on the effects of extra virgin olive oil supplementation on rats fed a high-fat diet. However, it should be noted that this study was conducted on rats, not on humans. While rats and humans share many physiological similarities, they are still very different species. Effects on humans might differ.

The paper, “Extra virgin olive oil supplementation reduces inflammation in the arcuate nucleus of the hypothalamus and improves metabolic parameters in obese rats,” was authored by Ariadni Peres, Ricardo Dantas, Aline Ferreira, Ana Caroline Silveira, Giovana Raphaelli, Laís Felipe, Letícia Souza, Mariana Costa, Alessandra Machado, Diorlon Machado, Rodrigo Herrmann, Jade de Oliveira, Carlos Alexandre Netto, Angela Wyse, Carla Dalmaz, and Rachel Bast.

A neuroimaging study of young, healthy adults showed that consuming a milkshake did not, on average, result in a significant release of dopamine in the striatum region of the brain. While dopamine levels did increase in some individuals, this variability was not associated with whether a person had a normal weight, was overweight, or had obesity. The research was published in Cell Metabolism.

Ultra-processed foods are industrially manufactured products made mostly from refined ingredients and additives, with little or no whole foods. They are often engineered to be highly palatable, so that consuming them engages the brain’s reward circuits more intensely than natural foods do.

This is usually achieved by ensuring that ultra-processed foods contain large quantities of easily digestible sugars and fats. Because humans have separate neural pathways connecting the gut to the brain’s reward areas that are triggered by fats and sugars, eating foods rich in both is often more rewarding than eating foods rich in fats or in sugars alone. This is particularly true if these sugars and fats are easier to digest than those found in natural foods, as is the case with many industrially added sugars and fats.

This intense reward potential has led to a popular theory that ultra-processed foods may be addictive. The core of this theory is the idea that their consumption elicits an outsized dopamine response in the brain’s reward regions, a surge similar in nature to that caused by drugs of abuse.

According to this model, this powerful initial reward reinforces consumption. Over time, repeated exposure is thought to cause the brain to adapt, leading to a down-regulation of dopamine receptors and a blunted response. This state, known as tolerance, could then compel an individual to consume even more of the food to achieve the same initial level of pleasure, creating a cycle of compulsive eating.

It was this hypothesis that study author Valerie L. Darcey and her colleagues set out to test. They investigated whether humans exhibited an exaggerated dopamine release after drinking a milkshake, a food frequently used in studies as a proxy for an ultra-processed product because it is rich in both easily digestible fat and sugars and often contains flavor-enhancing additives. Dopamine is a key neurotransmitter in this process; it is a chemical messenger that helps signal reward and motivation in the brain, reinforcing behaviors that lead to pleasurable or satisfying experiences.

Study participants were 50 young, healthy adults, 38 of whom were women. They were recruited to cover a full range of body mass index values, with roughly even numbers of participants with normal weight, overweight, and obesity.

After joining the study, participants were supplied with meals designed to provide the exact number of calories needed to maintain their current body weight for a period of 3-5 days. All meals were prepared in the NIH Clinical Center Nutrition Department Metabolic Kitchen with all foods and beverages weighed on a gram scale. Participants were instructed to consume all the foods and beverages they were given. Any food and beverages not consumed were returned and weighed. This procedure aimed to stabilize their diets.

After this period, participants were admitted to the center that carried out the study for several days, where they continued taking similar meals under observation. On the day of the experiment, participants first completed positron emission tomography (PET) scans of their brains in the morning, after having fasted overnight. After that, they rested for 75 minutes, at the end of which they received a glass of vanilla milkshake to consume.

Thirty minutes after drinking the milkshake, participants had their second PET scan. They also provided ratings of how pleasant the milkshake was, whether they wanted more, and how it compared to their expectations. Participants also completed several assessments of food-related behaviors, experiences, and depression.

Results showed no significant average increase in dopamine after drinking a milkshake in the striatum region of the brain. The study’s authors focused on the striatum because it is a brain region central to the reward system that processes dopamine signals. They found pronounced differences between individuals in how their striatum reacted to the milkshake, but these differences were not associated with participants’ adiposity.

In other words, while the brains of some individuals reacted to the milkshake by releasing dopamine, the brains of others did not, and the presence or intensity of this reaction was not related to a participant’s body weight.

Data indicated that dopamine responses might be related to how hungry participants felt and how enjoyable they found the milkshake to be. The dopamine response was also found to be weakly associated with the ad libitum (free) intake of ultra-processed cookies. This means that individuals whose brains reacted to the milkshake with a greater dopamine release tended to eat more cookies later when given the opportunity to eat as much as they wanted.

Discussing the findings in the context of whether ultra-processed foods can be considered addictive, the study’s authors concluded that “post-ingestive striatal dopamine responses to an ultra-processed milkshake were likely substantially smaller than for many addictive drugs and below the limits of detection using standard PET methods.”

The study contributes to the scientific understanding of neural processes related to food intake. However, the authors note that the study did not include a control group. The design compared dopamine levels before and after drinking the milkshake. Therefore, the possibility remains that other factors could have influenced the changes in dopamine observed in some individuals.

The paper, “Brain dopamine responses to ultra-processed milkshakes are highly variable and not significantly related to adiposity in humans,” was authored by Valerie L. Darcey, Juen Guo, Meible Chi, Stephanie T. Chung, Amber B. Courville, Isabelle Gallagher, Peter Herscovitch, Paule V. Joseph, Rebecca Howard, Melissa La Noire, Lauren Milley, Alex Schick, Michael Stagliano, Sara Turner, Nicholas Urbanski, Shanna Yang, Nan Zhai, Megan S. Zhou, and Kevin D. Hall.

A study of adult social media users in Italy suggested that loneliness and death anxiety might mediate the relationship between attachment anxiety and problematic social media use. The paper was published in Death Studies.

Attachment anxiety is a form of insecure attachment characterized by fear of rejection and excessive need for closeness in relationships. People with attachment anxiety constantly worry that their partner does not love them enough or will eventually leave them.

This persistent fear can lead to clingy or overly dependent behaviors as they seek reassurance. Even minor signs of distance or withdrawal from a partner can trigger intense distress or jealousy. Such individuals tend to be highly sensitive to changes in tone, attention, or affection. Their self-esteem is often highly dependent on how they are treated by significant others.

Attachment theory proposes that this form of anxiety develops from inconsistent caregiving during childhood, where affection and attention were unpredictable. In adulthood, it can make relationships emotionally exhausting and unstable.

Study author Alessandro Musetti and his colleagues hypothesized that attachment anxiety contributes to problematic social media use through a chain of psychological factors. They proposed that this relationship is mediated first by loneliness and then by death anxiety. Citing Terror Management Theory, they noted that individuals often cope with existential anxiety by seeking “symbolic immortality”—a sense of being part of something larger that will outlast them. The authors suggest that individuals with attachment anxiety may turn to social media to build a lasting digital presence as a way of achieving this symbolic immortality.

The study included 799 Italian adults (52% women) with an average age of 32. Regarding education, 54% had finished high school and 16% had a bachelor’s degree. In terms of employment, 31% were employed full-time, while 27% were students.

They completed a survey containing assessments of attachment anxiety (the Relationship Questionnaire), loneliness (the UCLA–Loneliness Scale), death anxiety (the Death Anxiety Scale), and problematic social media use (the Bergen Social Media Addiction Scale). Problematic social media use is a pattern of excessive or compulsive engagement with social media that interferes with daily functioning, relationships, or mental well-being.

Results showed that attachment anxiety was positively correlated with the other measured traits. Individuals with higher attachment anxiety also tended to report greater loneliness, stronger death anxiety, and more symptoms of problematic social media use.

The researchers’ statistical model revealed a nuanced set of relationships. First, it showed that two forms of loneliness—isolation (lacking a social network) and relational disconnectedness (lacking intimate relationships)—each helped explain the link between attachment anxiety and problematic social media use. More specifically, the model supported a sequential pathway: attachment anxiety was linked to higher relational disconnectedness, which in turn was linked to greater death anxiety, which finally was associated with problematic social media use. This specific chain of events was not found for the other types of loneliness.

“These findings underscore the significance underlying psychological processes in PSMU [problematic social media use], suggesting potential avenues for targeted interventions that address attachment-related insecurities, relational disconnectedness, and existential concerns,” the study authors concluded.

The study contributes to the scientific understanding of the consequences of attachment anxiety. However, it should be noted that the design of the study does not allow any definitive causal inferences to be derived from the results. The statistical model tested and supported by data only shows that the state of relationships it proposes is possible, not that it is definitely true.

The paper, “Attachment anxiety, loneliness, and death anxiety in problematic social media use,” was authored by Alessandro Musetti, Alessandro Alberto Rossi, Mattia Pezzi, Stefania Mannarini, Vittorio Lenzo, and Adriano Schimmenti.

A study of older adults in Japan found that taking a hot-tub bath before bed was associated with better sleep quality. Participants not only felt their sleep was better, but objective actigraphy data also confirmed they slept more efficiently on average compared to their peers who did not bathe before bed. This effect was particularly strong during winter. The paper was published in Sleep Health: Journal of the National Sleep Foundation.

Sleep quality refers to how well a person sleeps, including how long it takes to fall asleep, how often they wake during the night, and how rested they feel upon waking. It is not just the number of hours slept but the depth and continuity of sleep that determine its quality. High-quality sleep involves cycling smoothly through the stages of light, deep, and REM sleep without frequent interruptions.

Poor sleep quality can result from stress, irregular schedules, caffeine, alcohol, or sleep disorders like insomnia or sleep apnea. Good sleep quality supports brain function, learning, and emotional stability. It also plays a key role in physical health, aiding immune function, tissue repair, and hormone balance. Chronic poor sleep increases the risk of heart disease, obesity, diabetes, and depression. People who sleep poorly often experience daytime fatigue, poor concentration, and irritability.

Study author Yoshiaki Tai and his colleagues wanted to explore the effects of hot-tub bathing on sleep quality under real-life conditions, accounting for various factors such as bathing behaviors, environmental influences, and individual characteristics.

Hot-tub bathing is a common evening or nighttime practice in Japan. It involves being immersed in a tub filled with water heated to 40–41°C for 10–30 minutes. The bathtub is usually designed to have a depth that allows the water level to reach the mid-thorax or neck.

The researchers note that previous studies reported that hot-tub bathing before sleep was associated with lower nighttime blood pressure and a lower prevalence of nocturia (waking up from sleep to urinate).

The study included 2,252 older adults from Nara, Japan. Their average age was 69 years, and 64% were women.

Study participants wore an actigraph on the wrist of their non-dominant hand for seven consecutive 24-hour periods. An actigraph is a device that measures movement to estimate an individual’s sleep patterns, activity levels, and circadian rhythms. They also wore a wireless device that logged their skin temperature attached to the actigraph, and another temperature logger on their abdomen (however, the abdominal one was worn for 24 hours only).

Participants completed an assessment of sleep quality (the Pittsburgh Sleep Quality Index) and kept a diary of their bathing behavior. They recorded whether they took a hot-tub bath, a shower, or did not bathe before bed, as well as the start and end times of bathing and the duration of immersion. For a majority of the participants, this diary was for one day only, but 945 of them recorded it for the full 7-day period.

The study authors used these data to estimate the temperature of the water (using abdominal skin temperature as a surrogate) and the bath-to-bed interval. Baths taken more than 5 hours and 45 minutes before bedtime were classified as not having been taken before bedtime.

The results showed that participants who took a hot-tub bath before going to bed slept better than their peers who did not. Their odds of reporting poor sleep quality were significantly lower than the odds for participants who did not bathe. The odds of poor sleep for participants who took a shower were not significantly different from those who did not bathe.

Higher water temperature during bathing and longer immersion time were associated with more efficient sleep. However, there was a negative interaction between these two factors. If the water temperature went above 41.7°C or immersion lasted longer than 18.3 minutes, further increases were no longer beneficial and were associated with reduced sleep efficiency.

Furthermore, the association between hot-tub bathing and more efficient sleep was strongest and most consistent for participants studied during the winter months. In general, subjective sleep assessments agreed with actigraphy measures, indicating better sleep for participants taking hot-tub baths.

“Hot-tub bathing was associated with better self-reported sleep quality, higher SE [sleep efficiency], and shorter WASO [wake after sleep onset] in real-life settings among community-dwelling older adults. In hot-tub bathing sessions with a duration of immersion < 18.3 minutes and proximal skin temperature during bathing (used as a surrogate for water temperature in the bathtub) < 41.7°C, a longer duration of immersion and higher maximum proximal skin temperature during bathing were positively associated with higher SE [sleep efficiency]. Our results suggest that improvements in SE, WASO [wake after sleep onset], and SOL [sleep onset latency, how long it takes to fall asleep] can be maximized when hot-tub bathing is scheduled 61–120 minutes before bedtime during winter,” the study authors concluded.

The study sheds light on the links between bathing behaviors and sleep quality. However, it should be noted that this was an observational study, and researchers did not direct participants’ bathing behaviors. Because of this, definitive causal inferences cannot be drawn from the results.

The paper, “Association between before-bedtime hot-tub bathing and sleep quality in real-life settings among community-dwelling older adults,” was authored by Yoshiaki Tai, Kenji Obayashi, Yuki Yamagami, and Keigo Saeki.