ABSTRACT
Food is essential for health. Health is an essential purpose of a sustainable diet. Diet's role in health can be both direct and indirect. This chapter reviews the links between diet and health, placing this as a key component of sustainability. Obesity occurs when energy intake from food and drink consumption is greater than energy expenditure through the body's metabolism and physical activity over a prolonged period, resulting in the accumulation of excess body fat. Increases in the rate of obesity in Western countries have coincided with substantial changes in the availability of food, food consumption and the food environment. Portion sizes have increased considerably over the past 20 years, particularly for food eaten outside of the home. The energy density of the diet has also been linked to higher body mass index, obesity and increased waist circumference. Eating out, which has been a growing trend during recent decades, has also been associated with weight gain.
