Revisited: the real science of weight loss

Science Weekly

The Guardian

Science

4.2 • 1K Ratings

🗓️ 1 January 2026

⏱️ 22 minutes

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Summary

Kevin Hall spent 21 years at the US National Institutes of Health and became known globally for his pioneering work on ultra-processed foods. In April he unexpectedly took early retirement, citing censorship under the Trump administration. Now he has co-authored a book with the journalist Julia Belluz that aims to bust myths and challenge wellness orthodoxy on everything from weight loss and metabolism to supplements and wearables. In this episode from October, Hall tells Ian Sample what he wants us all to understand about diet, exercise and weight loss, and what led to his departure from the job he loved. Help support our independent journalism at theguardian.com/sciencepod

Transcript

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0:00.0	This is The Guardian.
0:03.5	Hi, Ian here.
0:09.4	We're on a break at Science Weekly, but we'll be back on Tuesday with a new episode.
0:14.9	As January begins and the diet industry ramps up its often confusing messaging,
0:20.8	we thought it was worth revisiting this
0:22.7	conversation with Kevin Hall, a leading expert on nutrition. We discussed diet myths, why ultra-processed
0:30.3	foods aren't all bad, and why he left his dream job after Robert F. Kennedy Jr. became his boss. I hope you enjoy it.
0:43.3	When Robert F. Kennedy Jr. was appointed as Donald Trump's health secretary, he came
0:49.1	with promises to tackle the broken food system. We shouldn't be giving 60% of the kids in school processed food that is making them sick.
0:59.1	We shouldn't be spending 10% of the SNAP program on sugar drinks.
1:04.7	And for one researcher at the forefront of nutrition science, this seemed like good news.
1:10.7	The rhetoric is spot on on those topics,
1:12.9	and that's one of the reasons we were excited to have the potential opportunity
1:16.3	to expand on our research and provide answers to the questions that Americans deserve.
1:22.4	Kevin Hall is admired by scientists around the world.
1:26.7	His groundbreaking research at the U.S US National Institutes of Health involves getting volunteers
1:32.6	into the lab and studying in minute detail how the modern food environment affects their
1:38.6	bodies.
1:39.7	But when his findings didn't fit the administration's narrative, he says they were downplayed.
1:48.0	The top research for the National Institutes of Health shocked the scientific and medical communities this week by announcing his early retirement and blaming it on censorship from RFK Junior's administration.
2:00.0	The Department of Health and Human Services has rejected his claims of censorship.
2:06.2	Now Kevin's on the outside, continuing to follow the evidence.
	...

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