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Why a high fat diet could reduce the brain’s ability to regulate food intake

Calorie intake is regulated in the short-term by cells called astrocytes (large star-shaped cells in the brain that regulate many different functions of neurons in the brain) that control the signalling pathway between the brain and the gut. Continuously eating a high fat/calorie diet seems to disrupt this signalling pathway.

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Regularly eating a high fat/calorie diet could reduce the brain’s ability to regulate calorie intake. New research in rats published in The Journal of Physiology found that after short periods of being fed a high fat/high calorie diet, the brain adapts to react to what is being ingested and reduces the amount of food eaten to balance calorie intake. The researchers from Penn State College of Medicine, US, suggest that calorie intake is regulated in the short-term by cells called astrocytes (large star-shaped cells in the brain that regulate many different functions of neurons in the brain) that control the signalling pathway between the brain and the gut. Continuously eating a high fat/calorie diet seems to disrupt this signalling pathway.

Understanding the brain’s role and the complex mechanisms that lead to overeating, a behaviour that can lead to weight gain and obesity, could help develop therapies to treat it. Obesity is a global public-health concern because it is associated with increased risk of cardiovascular diseases and type 2 diabetes. In England, 63% of adults are considered above a healthy weight and around half of these are living with obesity. One in three children leaving primary school are overweight or obese1.

Dr Kirsteen Browning, Penn State College of Medicine, US, said, “Calorie intake seems to be regulated in the short-term by astrocytes. We found that a brief exposure (three to five days) of high fat/calorie diet has the greatest effect on astrocytes, triggering the normal signalling pathway to control the stomach. Over time, astrocytes seem to desensitise to the high fat food. Around 10-14 days of eating high fat/calorie diet, astrocytes seem to fail to react and the brain’s ability to regulate calorie intake seems to be lost. This disrupts the signalling to the stomach and delays how it empties.”

Astrocytes initially react when high fat/calorie food is ingested. Their activation triggers the release of gliotransmitters, chemicals (including glutamate and ATP) that excite nerve cells and enable normal signalling pathways to stimulate neurons that control how the stomach works. This ensures the stomach contracts correctly to fill and empty in response to food passing through the digestive system. When astrocytes are inhibited, the cascade is disrupted. The decrease in signalling chemicals leads to a delay in digestion because the stomach doesn’t fill and empty appropriately.

The vigorous investigation used behavioural observation to monitor food intake in rats (N=205, 133 males, 72 females) which were fed a control or high fat/calorie diet for one, three, five or 14 days. This was combined with pharmacological and specialist genetic approaches (both in vivo and in vitro) to target distinct neural circuits. Enabling the researchers to specifically inhibit astrocytes in a particular region of the brainstem (the posterior part of the brain that connects the brain to the spinal cord), so they could assess how individual neurons behaved to studying rats’ behaviour when awake.

Human studies will need to be carried out to confirm if the same mechanism occurs in humans. If this is the case, further testing will be required to assess if the mechanism could be safely targeted without disrupting other neural pathways.

The researchers have plans to further explore the mechanism. Dr Kirsteen Browning said, “We have yet to find out whether the loss of astrocyte activity and the signalling mechanism is the cause of overeating or that it occurs in response to the overeating. We are eager to find out whether it is possible to reactivate the brain’s apparent lost ability to regulate calorie intake. If this is the case, it could lead to interventions to help restore calorie regulation in humans.”

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Could your oral health be affecting fertility?

Chronic oral inflammation may impair female fertility by triggering a systemic immune response that affects the ovaries. A new study shows this leads to oxidative damage, reduced egg quality, disrupted follicle development and reduced live birth rate. These findings point to a potential biological link between oral health and unexplained infertility, opening new directions for future treatments.

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A new study led by Prof. Michael Klutstein at the Hebrew University of Jerusalem and Prof. Asaf Wilensky at the Hebrew University-Hadassah Medical center and spearheaded by the students Dr. Paz Kles and Stephen Ameho has uncovered a striking biological link between chronic oral inflammation and female fertility, suggesting that conditions in the mouth may have far-reaching effects on reproductive health.

Published in the Journal of Dental Research, the study shows that persistent inflammation in the oral cavity can impair ovarian function, reduce egg quality, and ultimately lower fertility rates.

Researchers examined in a mouse model inflammation associated with dental implants, a common clinical scenario, and tracked how immune signals spread throughout the body. Their findings reveal that inflammation does not remain confined to the oral cavity but triggers a systemic immune response that reaches the ovaries.

The consequences were significant. Chronic oral inflammation in the animals was linked to increased levels of inflammatory cytokines in the ovaries, along with shifts in immune cell populations. This was accompanied by oxidative damage to ovarian tissue, impaired development of follicles, and reduced quality of oocytes.

These biological changes translated into measurable reproductive outcomes, with markedly reduced birth rates observed under inflammatory conditions in the animals.

The study also identified deeper cellular effects. Oocytes exhibited DNA damage and epigenetic alterations resembling those seen in reproductive aging, pointing to a possible mechanism by which inflammation accelerates the decline in fertility.

“Inflammation is often thought of as a localized response, but our findings show that it can have systemic consequences that extend as far as the reproductive system,” said Prof. Michael Klutstein. “This work suggests that chronic oral inflammation may be an underrecognized factor in female infertility, potentially contributing to cases that currently have no clear explanation.”

The findings add to growing evidence that oral health is closely linked to overall health. Chronic oral inflammatory conditions such as periodontitis are widespread and have already been associated with a range of systemic diseases.

The researchers note that further investigation in clinical settings will be essential to determine how these findings translate to patient care. If confirmed, the work could open new avenues for diagnosis and treatment, including the use of anti-inflammatory or antioxidant approaches to improve fertility outcomes.

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Maintaining a healthy heart may require regular doses of positivity

The findings of this study further point to the importance of attending to mental and behavioral health for cardiovascular disease prevention and cardiovascular health optimization.

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Positive psychology interventions such as mindfulness, gratitude journaling and optimism training can consistently improve blood pressure, inflammation markers and other cardiovascular disease risk factors within a matter of weeks, a recent study found. However, since these benefits are associated with lifestyle changes such as eating healthier and greater physical activity, the researchers suggested that ongoing reinforcements may be needed to stay on course long term.

Rosalba (Rose) Hernandez, a professor of social work at the University of Illinois Urbana-Champaign, led a team that analyzed the findings of 18 randomized controlled trials that used positive psychological and mindfulness interventions to enhance mental or physical health.

The programs that the team reviewed included individual methods — such as structured telephone sessions, journaling with brief check-ins and digital platforms such as apps and text messaging — and interactive in-person group sessions, as well as hybrid formats that blended these with online tools and virtual meetings. Most of the programs consisted of weekly sessions and at-home activities that reinforced the skills taught, with the majority of programs lasting from six to 12 weeks, the team found.

In general, the programs included 50-200 adults with elevated cardiovascular risk factors such as uncontrolled hypertension, heart failure or other conditions. Typically, the participants were in their late 50s to mid-60s, and women comprised 35-55% of the samples across those studies that reported their participants’ gender, according to the researchers.

“In hypertension and postacute coronary syndrome cohorts, mindfulness-based programs delivered over an eight-week period reduced systolic blood pressure and lowered inflammatory markers such as high-sensitivity C-reactive protein and fibrinogen,” said Hernandez, who is a Fellow of the American Heart Association. “A 12-week spirituality-based digital intervention achieved one of the largest reductions — reducing systolic blood pressure measured with a standard cuff by 7.6 points, and central systolic pressure — which is measured in the aorta as it leaves the heart — by 4.1 points.”

In prior research on positive psychology interventions, scientists seldom defined the dose that was needed to obtain the beneficial effects, Hernandez said. She and the team members sought to clarify the frequency and duration that was most likely to improve individuals’ cardiovascular health.

Programs that had more frequent contact with their participants yielded the most consistent physiological benefits, underscoring the opportunity to embed positive psychological strategies into long-term cardiovascular care, Hernandez said.

The team found that the strongest behavioral improvements were achieved by an eight-week program delivered over WhatsApp that combined weekly sessions with daily microtasks, motivating participants to engage in greater physical activity, eat a healthier diet and take their medication as prescribed. A program that included motivational interviewing succeeded in increasing cardiac patients’ levels of physical activity by 1,800 steps a day and their medication adherence, while the mindfulness programs improved participants’ activity levels and diets only, according to the study.

“The therapeutic dose that was most consistently linked with improvements in blood pressure, inflammation and endothelial function was daily practice reinforced by weekly sessions over eight to 12-week periods,” Hernandez said. “Therapeutic dosing typically involved high-frequency dosing over this time period to obtain short-term physiologic benefits, while ongoing less-intensive contact may be needed to sustain behavioral change.”

Published in the journal Cardiology Clinics, the study was co-written by University of South Florida social work professor Soonhyung Kwon; Alyssa M. Vela, a professor of surgery and of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine; and Katharine S. Edwards, a professor of cardiovascular medicine and of psychiatry and behavioral medicine at Stanford Medicine.

“The findings of this study further point to the importance of attending to mental and behavioral health for cardiovascular disease prevention and cardiovascular health optimization,” Vela said. “This speaks to the need for routine screening and integration of cardiac behavioral medicine to allow for access to important interventions.”

The current study adds to a growing body of research linking psychological well-being — including traits such as optimism, positive affect and gratitude — with cardioprotective benefits.

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Heart disease risk may start in the womb, study finds

Young adults whose mothers had high blood pressure during pregnancy — either pregnancy-associated hypertension, pre-eclampsia or eclampsia — had more signs of early arterial injury, higher blood pressure, higher body mass index and higher blood sugar than peers.

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A child’s future heart health may be partially shaped before they are born, reports a new Northwestern Medicine study that found pregnancy complications are linked to poorer cardiovascular health in offspring more than 20 years later.

The study found that young adults whose mothers had high blood pressure during pregnancy — either pregnancy-associated hypertension, pre-eclampsia or eclampsia — had more signs of early arterial injury, higher blood pressure, higher body mass index and higher blood sugar than peers.

The authors said the study adds to growing evidence that cardiovascular risk may be transmitted across generations through a combination of biological, environmental and behavioral factors.

“That means we must make sure people maintain good health from childhood into young adulthood, so that if or when someone becomes a parent, they pass on the best opportunity for good health to their children,” said study senior author Dr. Nilay Shah, assistant professor of medicine in the division of cardiology at Northwestern University Feinberg School of Medicine.

How the study was conducted

Shah and colleagues evaluated nearly 1,350 mother-child pairs from the Future of Families and Child Well-Being Study, which enrolled mothers and children at birth between 1998 and 2000 across 20 U.S. cities. The children were then followed into adulthood.

Using delivery hospitalization records, the Northwestern scientists first identified whether mothers experienced pregnancy complications, including high blood pressure during pregnancy, gestational diabetes (high blood sugar during pregnancy) or preterm birth (before 37 weeks of pregnancy).

The three pregnancy complications are on the rise, and affect almost one in four pregnancies in the U.S.

The research team then analyzed cardiovascular health of offspring at age 22, using blood pressure measurements, blood testing, body mass index assessments and carotid artery ultrasounds to look for signs of artery injury.

Finally, the scientists compared participants with and without exposure to each pregnancy complication and adjusted for factors like income, education, difference in birth weight and smoking during pregnancy.

Key findings

At around age 22, participants whose mothers had high blood pressure during pregnancy had:

  • Higher body mass index (+2.8 BMI points)
  • Higher diastolic blood pressure (+2.3 mm Hg)
  • Higher blood sugar levels (+0.2% HbA1c)
  • Thicker artery walls (~0.02 mm)

While the difference in artery wall thickness may seem small, the study authors said it corresponds to roughly three to five years of additional vascular aging. That means arteries looked older and less healthy than expected, which raises the risk of future heart disease.

Other pregnancy complications also showed some long-term effect:

  • Exposure to gestational diabetes was linked to worse blood pressure and some evidence of artery thickening
  • Being born preterm was associated with higher blood sugar levels

‘Most heart disease is preventable’

With pregnancy complications on the rise in the U.S., Shah said the study provides compelling evidence that improving health before and during pregnancy could help reduce heart disease risk in the next generation.

“There is evidence that both parents’ health at the time of conception and during pregnancy influences a child’s health,” he said. “So, promoting health from an early age, like exercising regularly, eating healthfully, never smoking and getting enough sleep, is not just meant for an individual, but doing so may help future generations be healthier, too.”

Shah also emphasizes that risk is not destiny.

“The good news is that most heart disease is preventable,” he said. “If you experienced high blood pressure or high blood sugar during pregnancy, or your child was born early, it does not absolutely mean that your child will have worse health as adults. But I would encourage you to pay attention now to your child’s health behaviors.

“What children learn in childhood sets the stage for their health across their lives. If you are wondering whether your children’s behaviors are healthy, or are considering making a change, please speak with your child’s pediatrician for advice and guidance.”

Other Northwestern co-authors include Emily Lam, Abigail Gauen, Dr. Sadiya Khan, Alexa Freedman and Norrina Allen.

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