Diet plays an important role in the genesis of obesity. Personal choices, food advertising, social customs and cultural influences, as well as food availability and pricing all play a role in determining what and how much an individual eats. Dietary energy supply The dietary energy supply is the food available for human consumption, usually expressed in kilocalories per person per day. It gives an overestimate of the total amount of food consumed as it reflects both food consumed and food wasted. The per capita dietary energy supply varies markedly between different regions and countries. It has also changed significantly over time. From the early 1970s to the late 1990s, the average calories available per person per day (the amount of food bought) has increased in all part of the world except Eastern Europe and parts of Africa. The United States had the highest availability with 3654 kilo calories per person in 1996. This increased further in 2002 to 3770. During the late 1990s, Europeans had 3394 kilo calories per person, in the developing areas of Asia there were 2648 kilo calories per person, and in sub-Sahara Africa people had 2176 kilo calories per person. Average calorie consumption From 1971 to 2000, the average daily number of calories which women consumed in the United States increased by 335 calories per day (1542 calories in 1971 and 1877 calories in 2000). For men, the average increase was 168 calories per day (2450 calories in 1971 and 2618 calories in 2000). Most of these extra calories came from an increase in carbohydrate consumption, though there was also an increase in fat consumption over the same time period. The increase in caloric consumption is attributed primarily to the "consumption of food away from home; increased energy consumption from salty snacks, soft drinks, and pizza; and increased portion sizes". Other sources note that the consumption of soft drinks and other sweetened beverages now accounts for almost 25 percent of daily calories in young adults in America. As these estimates are based on a person's recall, they may underestimate the amount of calories actually consumed. Fast food As societies become increasingly reliant on energy-dense fast-food meals, the association between fast food consumption and obesity becomes more concerning. In the United States, consumption of fast food meals has tripled and calorie intake from fast food has quadrupled between 1977 and 1995. Consumption of sweetened drinks is also