Lifestyle diseases (also sometimes called diseases of longevity or diseases of civilization interchangeably) are diseases that appear to increase in frequency as countries become more industrialized and people live longer. They can include Alzheimer's disease, atherosclerosis, asthma, some kinds of cancer, chronic liver disease or cirrhosis, Chronic Obstructive Pulmonary Disease, Type 2 diabetes, heart disease, metabolic syndrome, chronic renal failure, osteoporosis, stroke, depression and obesity.
Some commenters maintain a distinction between diseases of longevity and diseases of civilization. Certain diseases, such as diabetes, dental caries or asthma appear at greater rates in young populations living in the "western" way; their increased incidence is not related to age, so the terms cannot accurately be used interchangeably for all diseases.
Diet and lifestyle are major factors thought to influence susceptibility to many diseases. Drug abuse, tobacco smoking, and alcohol drinking, as well as a lack of exercise may also increase the risk of developing certain diseases, especially later in life.
In many Western countries, people began to eat more meat, dairy products, vegetable oils, sugary foods, and alcoholic beverages during the latter half of the 20th century. People also developed sedentary lifestyles and greater rates of obesity. Rates of colorectal cancer, breast cancer, prostate cancer, endometrial cancer and lung cancer started increasing after this dietary change. People in developing countries, whose diets still depend largely on low-sugar starchy foods with little meat or fat have lower rates of these cancers.
Death statistics in the United States 
In 1900, the top three causes of death in the United States were pneumonia/influenza, tuberculosis, and diarrhea/enteritis. Communicable diseases accounted for about 60 percent of all deaths. In 1900, heart disease and cancer were ranked number four and eight respectively. Since the 1940s, the majority of deaths in the United States have resulted from heart disease, cancer, and other degenerative diseases. And, by the late 1990s, degenerative diseases accounted for more than 60 percent of all deaths.
It should be noted, however, that lifestyle diseases have their onset later in an individual's life and need a longer lifespan in order to become the cause of death. This suggests that the life expectancy at birth of 49.24 years in 1900 was too short for degenerative diseases to occur, compared to a life expectancy at birth of 77.8 years in 2004. Also, survivorship to the age of 50 was 58.5% in 1900, and 93.7% in 2007.
See also 
- Pollan, Michael. In Defense of Food: An Eater's Manifesto. Penguin Press HC, The. ISBN 978-1-59420-145-5.
- Vaillant GE, Mukamal K. Successful Aging. Am J Psychiatry. 2001 Jun 1;158(6):839-847." PMID 11384887 Full Text Online
- Gary E. Fraser, David J. Shavlik. Ten Years of Life: Is It a Matter of Choice? Arch Intern Med. 2001;161:1645-1652. PMID 11434797 Full Text Online
- Steyn K; Fourie J; Bradshaw D. The impact of chronic diseases of lifestyle and their major risk factors on mortality in South Africa. S Afr Med J, 1992 Oct, 82:4, 227-31. PMID 1411817
- Key TJ, Allen NE, Spencer EA. The effect of diet on risk of cancer. Lancet. 2002 Sep 14;360(9336):861-8. Review. PMID 12243933
- National Center for Health Statistics, National Office of Vital Statistics, 1947 for the year 1900 (page 67), for the year 1938 (page 55).
- Olshansky, S. Jay; Carnes, Bruce A. (2002). The Quest for Immortality: Science at the Frontiers of Aging. W. W. Norton & Company. p. 191. ISBN 0393323277.
- Life expectancy by age, race, and sex, Centers for Disease Control and Prevention, FastStats, 2007, retrieved 2009-06-11
- Survivorship by age, race, and sex, Centers for Disease Control and Prevention, FastStats, 2007, retrieved 2009-06-11