Global fast food chains have significantly impacted food culture and trade around the world. McDonald's introduced fast food overseas when it was previously unknown. The growth of fast food is linked to urban development and changing food demands. Major fast food chains from the US and UK established globally starting in the mid-20th century. While globalization of food chains affects economies, employment, and international relations, it can also threaten local food traditions and public health by promoting obesity. Alternatives are promoted such as buying local and fresh to support farmers while balancing costs and prices.