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.
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.
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 unhealthy food.
- Comfort food
- Glutamic acid (flavor), common flavoring compounds and their synthetic versions, which may be added to some processed foods, to boost their savoriness
- Health food, foods that tend to be nutrient rich, and may be eaten for their potential benefits to health
- List of food additives
- http://www.wordnetweb.princeton.edu/perl/webwn[dead link]
- junk food - Google Search
- O'Neill, Brendon (November 30, 2006). "Is this what you call junk food?". BBC News. Retrieved June 29, 2010.
- Larsen, Joeanne; MS, RD, LD http://www.dietitian.com/junkfood.html
- "What Makes a Food Junk?". Huffington Post. 4 August 2010.
- What Is Junk Food? (with pictures)
- Junk-Food Facts
- Johnson, Paul M.; Kenny, Paul J. (2010). "Addiction-like reward dysfunction and compulsive eating in obese rats: Role for dopamine D2 receptors". Nature Neuroscience 13 (5): 635–41. doi:10.1038/nn.2519. PMC 2947358. PMID 20348917.
- Goodwin, Jenifer. Junk Food 'Addiction' May Be Real. Business Week. March 29, 2010.[dead link]
- Craving for junk food 'inherited' Mothers who eat junk food during pregnancy may be condemning their children to crave the same diet, according to animal tests. BBC News. 14 August 2007.
- Clemens Bomsdorf. "Denmark Scraps Much-Maligned 'Fat Tax' After a Year". The Wall Street Journal. Retrieved 2012-11-14.
- "Welcoming the age of disease prevention". December 17, 2011.