by boosting a specific gene that strengthens blood vessels and cuts our risk of a heart attack. Scientists had already spotted a link between light and heart disease, noting the greater prevalence of heart attacks during winter months. But this study revealed something intriguing: Participants exposed to 30 minutes of intense light between 8:30 and 9 a.m. for five consecutive days had raised levels of a protein called PER2.
But a newer theory posits that we eat less after being active because of a hormone called growth differentiation factor 15 , which our bodies produce when we move . Researchers know that GDF-15 suppresses appetite in rodents and monkeys and are now . Either way—heat or hormone—an early-morning walk may well curb excessive feelings of hunger, helping us regulate and moderate our appetite. After 14 years of walking dogs and children every morning, I found myself addicted to a start-of-the-day romp. Now, like Martineau, I appreciate the opportunity to collect myself, to plan my day: The health benefits are a serendipitous byproduct.