People on weight-loss or other diets containing less than 1,200 calories may not be eating enough food to meet their vitamin needs. Increased physical activity would allow these individuals to consume substantially more calories without weight gain. Mild exercise such as walking would stimulate the appetite of elderly people, whereas more vigorous exercise for the dieters would burn off the additional calories and avoid weight gain.
Improved food choices, especially foods of high nutrient density, also boost vitamin levels. Fruits and vegetables, fish and poultry, skim milk, and whole-grain breads are examples of foods that supply substantial amounts of vitamins per calorie.
The choice of how to meet your nutritional requirements is really up to you. Nutrition is a science, and individuals vary widely in their needs and habits. In developing the RDA, nutrition scientists allow for a safety margin in addition to determining the amounts needed to prevent deficiency. Some circumstances can create needs which tap this margin but almost never exceed it.