Intermittent fasting, AI chatbots and mental health, and endurance running's impact on red blood cells: NPR Shortwave science roundup

Three science stories explore intermittent fasting and weight loss, AI chatbots and mental health, and how ultra-endurance running affects red blood cells. A meta-analysis indicates intermittent fasting may not outperform traditional dieting for weight loss in overweight adults, with study size limiting certainty. The piece also discusses concerns about AI chatbots and mental health, including the effectiveness of reminders that users are speaking to a machine and the need for open data to inform policy. Finally, researchers show that extreme endurance running can damage red blood cells, though long-term health implications remain unclear and regular exercise remains a key健康 tool.

Intermittent fasting and weight loss: what the meta-analysis shows

This episode begins with a biweekly science roundup focusing on running, dieting and mental health tools, and the physiology of extreme exercise. The first story centers on intermittent fasting and weight loss. An international team analyzed 22 smaller studies that compared intermittent fasting to other dietary approaches or to doing nothing. The conclusion they reached was that intermittent fasting did not outperform traditional dietary advice or inaction for weight loss in overweight or obese adults. The researchers cite the small size and variability of the included studies as a limitation, making it hard to draw firm conclusions about how fasting compares with other strategies over the long term. While the review targets weight loss as the standard, the hosts emphasize that reasons for trying intermittent fasting can extend beyond weight management, including metabolic and health considerations. They also contrast the outcomes with GLP-1–based therapies, which can produce more substantial weight loss for some patients, though those treatments come with their own risks and considerations.

"the results of this literature review really focused in on weight loss as the standard. But like you said, that's not the only reason people choose to try intermittent fasting." - Mary Louise Kelly

Chatbots and mental health: reminders and policy implications

The second story examines how AI chatbots intersect with mental health, including troubling cases in which chatbot interactions have been linked to suicide concerns. The report notes testimony from families about experiences where a chatbot allegedly contributed to a suicidal act, and discusses regulatory responses such as California and New York requiring AI chatbots to flag their non-human status at regular intervals. The piece features perspectives from social scientists Linnea Estadius and Celeste Campos Castillo, who caution that reminders that an interlocutor is not human may have mixed effects and could even be destabilizing for some users. The interviewees argue for more transparent data sharing to study these interventions and inform policy, highlighting potential downsides and the need for careful evaluation of safety measures in digital health tools.

"If someone already feels lonely or if they're struggling with their mental health, a reminder that they're not talking to a real person could destabilize them and make them feel more isolated." - Celeste Campos Castillo

Ultra endurance running: red blood cell damage and the limits of extreme exercise

The final topic investigates how ultra endurance running affects the body. The researchers compared runners who covered 24 miles (roughly a half marathon’s distance in some contexts) to those who completed 106-mile ultramarathons. Blood samples taken before and after the races showed damage to red blood cells in both groups, with greater inflammation markers and different damage profiles in the ultramarathon cohort. The study’s author Travis Nemkov explains that higher oxygen demands drive faster blood circulation, which can lead to red blood cell breakdown. However, the team notes the body’s capacity to generate new red blood cells and that the long-term implications remain unknown due to the study’s small size and short follow-up. The takeaway remains that regular exercise is beneficial, and extreme endurance activity should be approached with caution and individual guidance from medical professionals.

"When you're doing something like running, your body needs more oxygen, and that means blood is circulating through your body more quickly, which can lead to the breakdown of red blood cells." - Travis Nemkov