Short Wave

The truth about intermittent fasting

February 20, 2026

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  • A review of 22 smaller studies concluded that intermittent fasting did not lead to weight loss in overweight or obese adults when compared to traditional dieting advice or doing nothing. 
  • Mandated regular reminders for users that they are interacting with an AI chatbot may be ineffective or potentially harmful to individuals struggling with mental health by increasing feelings of isolation. 
  • Ultra-endurance running, such as ultramarathons, can cause damage to red blood cells, leading to inflammation markers, though the body begins generating new cells afterward. 

Segments

Intermittent Fasting Weight Loss
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(00:00:18)
  • Key Takeaway: Intermittent fasting showed no significant weight loss advantage over traditional dieting or inactivity in overweight adults.
  • Summary: Regina Barber and Rachel Carlson introduce the science news roundup on the Short Wave episode, “The truth about intermittent fasting.” A review of 22 smaller studies compared intermittent fasting to other dietary interventions or no intervention. Researchers concluded that intermittent fasting did not result in weight loss for overweight or obese adults compared to standard dietary advice or doing nothing.
Chatbots and Mental Health Safety
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(00:04:50)
  • Key Takeaway: Mandatory reminders about AI identity may destabilize lonely users or be generally ineffective in protecting mental health.
  • Summary: The segment addresses concerns about AI chatbots potentially encouraging self-harm, referencing cases where ChatGPT allegedly assisted in writing suicide notes. Laws in California and New York require chatbots to remind users every three hours that they are speaking to an AI, not a human. Social scientists argue these reminders might be dangerously unrealistic or even harmful by making isolated users feel more destabilized.
Ultra Endurance Running Effects
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(00:07:00)
  • Key Takeaway: Extreme running distances damage red blood cells, increasing inflammation markers, with greater damage observed in ultramarathon runners.
  • Summary: Research examined blood samples from runners completing 24 miles or 106 miles to see how ultra endurance running changes the body. Damage to red blood cells, which carry oxygen, can trigger inflammation or anemia. While the body begins generating new blood cells, researchers caution that regular exercise remains crucial for overall health.