The truth about intermittent fasting

Short Wave

NPR

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4.7 • 6.5K Ratings

🗓️ 20 February 2026

⏱️ 9 minutes

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Summary

From TikTok and Instagram influencers to celebrities like Hugh Jackman and Kourtney Kardashian, intermittent fasting has gotten a lot of hype. The diet restricts what time you eat rather than what or how much you eat. The idea is that short periods of fasting cause your body to burn through stored fat reserves. But is that conventional wisdom true? And can it really contribute to weight loss? Regina G. Barber and Rachel Carlson tackle those questions — plus why some researchers are rethinking how to protect people's mental health when talking to chatbots and how ultra-endurance running changes the human body.

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Transcript

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0:00.0	You're listening to Shortwave from NPR.
0:05.9	Hey, Shortwaivers, Regina Barber here.
0:08.0	And Rachel Carlson.
0:09.3	And today we have our biweekly science news roundup featuring the hosts of all things considered.
0:14.0	And today we have the legend Mary Louise Kelly.
0:17.3	Woohoo! I'm so excited to be here and excited because I hear one of the stories you brought
0:22.2	is about running, which is like the only sport I can actually do. So I'm here for you.
0:27.6	Yes, we're talking about running. Also, why intermittent fasting might not be a good weight
0:32.1	loss solution. And rethinking how to protect people's mental health when they talk with a chatbot.
0:38.1	All that on this episode of Shortwave, the science podcast from NPR. Okay, Mary Louise, where should we start?
1:00.6	I want to hear all three of these. Okay, I have not had time to get lunch today, so I'm kind of doing intermittent fasting.
1:05.8	Oh, no.
1:06.9	So let's start there. This is, just to explain, this is where you restrict the times you eat, right, rather than what you eat?
1:13.8	Yeah, so some people might fast every other day. Others might eat between the hours of 10 to 6, but do a 16-hour fast outside of that.
1:21.8	The idea is that these short periods of fasting will cause your body to start burning through stored fat reserves.
1:28.3	The issue is we don't have a big, long-range study on how it compares with other types of dieting.
1:33.8	So an international team of scientists did the next best thing.
1:37.5	They looked at 22 smaller studies that compared intermittent fasting to other dietary interventions,
1:42.7	like eating less or eating specific types of foods. They also compared intermittent fasting to other dietary interventions, like eating less or eating specific types of foods.
1:45.8	They also compared intermittent fasting to doing nothing. And what did they find?
1:50.5	They concluded that intermittent fasting did not work for weight loss in overweight or obese adults,
1:56.0	as compared to either traditional dietary advice or even doing nothing. Huh. Okay, so it doesn't work.
	...

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