The Evidence and the Issues Philip Payne and Michael Lipton People can adjust to environmental changes by calling on a wide range of physical attributes, capabilities, and behaviors. For survival, probably the most important are those that make it possible to prevent serious imbalances between food energy needs and the amount of food that can be acquired at acceptable cost. Those who formulate food and agricultural policies need to know the scope, costs, and benefits of the more common adaptive strategies used by poor people, who are normally at greatest risk of energy stress. In particular, policymakers and analysts need to assess the scope and limits of adjustments by individuals or groups. An often bitter controversy surrounds this subject.
Recent research underscores the subtlety and complexity of the components of adaptive response.
Faced with a shortage of food, people appear first to decide to reduce discretionary activity or to modify the duration or intensity of economic work. Such behavioral changes reduce the pressure toward biological adaptation. In hard times, working adults may temporarily lose body weight. This loss is an adaptation to stress in the short run by using previously stored energy, and in the long run by reducing food energy requirements for maintaining subsequent smaller body weight. A similar principle applies to small children.