Five days of indulging in chocolate bars, crisps and other junk foods can lead to lingering changes in brain activity, a study shows1. The resulting brain patterns are similar to those seen in people who have obesity. A junk-food splurge shifted brain patterns in healthy young men despite their body weight and composition remaining unchanged, according to the study, published on 21 February in Nature Metabolism. “I didn’t expect the effect to be so clear in a healthy population,” says neuroscientist Stephanie Kullmann at the University of Tübingen in Germany, who led the study.
But another scientist says that there are limitations to the study, which relied on a nasal spray to deliver the digestive hormone insulin. “The authors give very large doses of insulin,” says physiologist Christoph Buettner, “four to five times the amount that a human releases into the bloodstream over 24 hours.” Buettner, at Rutgers Robert Wood Johnson Medical School in New Brunswick, New Jersey, was not involved in the study. Kullmann responds that not all of the inhaled insulin reached the brain and that more study is needed to pinpoint how much does. To read the full story.