Diet and obesity

Diet plays an important role in the genesis of obesity. Personal choices, 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.

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.

From 1971 – 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 rather than an increase in fat consumption. The primary sources of these extra carbohydrates were sweetened beverages, which 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.

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 meal has tripled and calorie intake from fast food has quadrupled between 1977 and 1995. Consumption of sweetened drinks is also believed to be a major contributor to the rising rates of obesity.

The portion size of many prepackage and restaurant foods has increased in both the United States and Denmark since the 1970s. Fast food servings, for example, are 2 to 5 times larger than they were in the 1980s. Evidence has shown that larger portions of energy-dense foods lead to greater energy intake and thus to greater rates of obesity.

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