One of the biggest problems in sustainability has nothing to do with food production; it is about our eating habits. The requirements of energy for one person varies with age, sex and activity but an overall energy needs is a value among 2,000 and 2,600 kilocalories per day (NI 1991, Whitney & Rolfes 1993). The problem with our eating habits is when people eat almost double of their daily energy needs. For example, Figures 12 and 13 illustrate that in some regions people have serious problems of obesity because people eat an average of more than 3,500 kcal per day (NI 1991, UNEP/GRID-Arendal 1999). In contrast, Figure 12 shows the top ten countries with the lowest daily calorie supply per person, where in countries like Mozambique people eat an average of 1,632 kcal per day (NI 1991). As a result, the highest consumptions of calories plus the population growth represent a big threat to our future food security. 

Figure 12. Top ten of countries that eat more and less kcal per day (from NI 1991)

Figure 13. Calorie consumption in selected regions of the world (1975-1995) (from UNEP/GRID-Arendal 1999).

One alternative to promote sustainability is to eat lower on the food chain. The demands of energy to produce meat are higher compared with the energy needed to produce plant foods. For example, to produce 1 kcal of grains demand 1/3 kcal of fossil energy, 1 kcal of fruits demand 2 kcal of fossil energy, and 1 kcal of meat requires 10 to 90 kcal of fossil fuels (Whitney & Rolfes 1993). In the USA about 17% of their total energy goes to support meat production (Whitney & Rolfes 1993). Similarly, Tilman and coworkers (2002) showed that 3-10 kilograms of grain are required to produce 1 kg of meat. Figure 14 illustrate the differences of three different diets and the energy required to feed these diets, where diets with high meat consumptions demand more energy compared with vegetarian diets (Whitney & Rolfes 1993). In conclusion, it is clear that in order to be more efficient and achieve sustainability we need to reduce our meat consumption.

Figure 14. People with three different diets of 3300 kcal and the fossil fuel amount necessary to produce these different diets (from Whitney & Rolfes 1993)