Junk food

Junk food is a derisive slang term for food that is of little nutritional value and often high in fat, sugar, salt, and calories. It is widely believed that the term was coined by Michael Jacobson, director of the Center for Science in the Public Interest, in 1972.

Junk foods typically contain high levels of calories from sugar or fat with little protein, vitamins or minerals. Foods commonly considered junk foods include salted snack foods, gum, candy, sweet desserts, fried fast food, and sugary carbonated beverages. Many foods such as hamburgers, pizza, and tacos can be considered either healthy or junk food depending on their ingredients and preparation methods. The more highly processed items usually fall under the junk food category. What is and is not junk food can also depend on the person's class and social status, with wealthier people tending to have a broader definition while lower-income consumers may see fewer foods as junk food, especially certain ethnic foods.

Despite being labeled as "junk," consuming such foods usually does not pose any immediate health concerns and is generally safe when integrated into a well balanced diet.

Health effects
A study by Paul Johnson and Paul Kenny at the Scripps Research Institute in 2008 suggested that junk food consumption alters brain activity in a manner similar to addictive drugs like cocaine and heroin. After many weeks with unlimited access to junk food, the pleasure centers of rat brains became desensitized, requiring more food for pleasure. After the junk food was taken away and replaced with a healthy diet, the rats starved for two weeks instead of eating nutritious fare. A 2007 British Journal of Nutrition study found that female rats who eat junk food during pregnancy increased the likelihood of unhealthy eating habits in their offspring.

Taxation
In an attempt to reduce saturated fat consumption, from December 2011 to November 2012 Denmark introduced the first fat-food tax in the world by imposing a surcharge on all foods (including natural ingredients) that contain more than 2.3 percent saturated fat. Hungary has also imposed a tax on packaged foods that contain unhealthy concentrations, such as beverages containing more than 20 mg of caffeine per 100 ml.

Norway taxes refined sugar, and Mexico has various excises on healthy food.