As part of the study, Johnson worked with researchers from San Diego State University, the Santa Fe Institute, and Johns Hopkins University to monitor queries from 2004 to 2012 for searches that included the word "healthy" or that were Google classified as "health-related" (e.g. healthy diet). Data showed that health-related queries on Monday and Tuesday were 3 percent greater than Wednesday, 15 percent greater than Thursday, 49 percent greater than Friday, 80 percent greater than Saturday and 29 percent greater than Sunday.

Johnson notes that the "rhythms were unfailingly consistent" across the weeks and were not influenced by factors such as media reporting on health. Knowing that healthy considerations follow a week-long cycle "opens the door for more targeted and, ultimately more effective, health promotion," Johnson said.

An estimated $76.2 billion is spent annually on health promotion programs—money Johnson suggests could be better spent "if everyone were timing their health messages to days of the week when people were most open to hearing them."

That's precisely the idea behind the Monday Campaigns, a joint project of Columbia University's Mailman School of Public Health, Johns Hopkins' Bloomberg School of Public Health, and the Syracuse University Newhouse School of Public Communications, where Johnson serves as research director. The Monday Campaigns' mission is simple: to make Monday the day we associate with healthy behaviors.

"Friday is payday. Saturday is play day. Sunday is pray day. We're trying to make Monday the 'all health breaks loose' day," said Sid Lerner, a former advertising executive who founded the Monday Campaigns.

So far, the Monday Campaigns' most successful initiative has been "Meatless Monday," a movement that asks carnivores to give up meat one day a week for both health and environmental reasons. On average, Americans consume 8 ounces of meat per day—45 percent more than the USDA recommends.

Cutting-back on red meat consumption, in particular, can reduce one’s risk for chronic preventable illnesses—such as colon cancer and heart disease—and help people live longer, healthier lives. The U.N. Food and Agriculture Organization also says reducing meat consumption can also help reduce greenhouse gas emissions—a leading cause of climate change—produced by the meat industry, and conserve natural resources, such as fresh water and fossil fuel, that are used to raise livestock.

Since its launch in 2003, Meatless Monday has made its way into corporate cafeterias, hospitals, K-12 schools, colleges, and local governments. It is supported by celebrities like Oprah and Sir Paul McCartney. Even meat-loving chef Mario Batali has joined the movement by offering Meatless Monday menu options in all of his 14 restaurants.

Meatless Monday is practiced in 31 countries worldwide in 21 different languages—a testament, Lerner says, "to the universal appeal of an idea that is easy to understand and easy to do." Most recently, the Norwegian Army took up Meatless Monday on one of its bases, with the intent to expand to its bases worldwide.