As in overweight, the first step is to see a physician and have a thorough physical examination. It is important to find and correct anything which may be wrong. Efforts to gain may be useless unless this is done. The same principles apply to gaining weight as to losing it, but in reverse. Underweight people must take in _more_ calories than they use, so that there will be some left over to store as fat. Will power can be as great a factor in gaining weight successfully as it is in losing, particularly for people who do not like many of the essential foods. They must learn to say “yes” to enough of the right foods, regardless of their wishes, just as firmly as their fat friends need to say “no” to forbidden extras. As in overweight, it is important first to include the essential foods in the day’s meals. These foods are necessary for maximum health, whether a person’s weight is too high, too low, or just right. Some underweight individuals whose food choices have been poor may find that they are able to gain merely by making sure that they include these foods in their diet. Others need to study ways to add extra calories. _Adding Extra Calories_ The simplest way is to eat more at each meal—extra bread and butter, and second helpings of everything. Often, however, underweight people seem to have a small stomach capacity. Therefore, additions of high-calorie foods which add little or no bulk are probably easier to take at first than trying to eat larger quantities. Such additions as cream on cereals and in beverages; extra eggs in puddings, salad dressings, and drinks; and butter or other fat used generously in salad dressings, cooking and seasoning should add enough calories to enable most people to gain weight. Also, provided they are added to regular meals and not used to replace them, the high-calorie foods listed on page 14 should be used freely by anyone trying to gain weight. If they do not interfere with eating enough at regular meals, between-meal snacks also help. So do extra milk and something to eat before going to bed. _Saving Energy_ The body uses fewer calories at rest than when active, and least of all during sleep. Therefore, any extra sleep or rest which an underweight person gets will help him to gain. Whatever energy can be saved during waking hours by riding instead of walking, sitting instead of standing, and relaxing as often as possible will add to the calories saved. A healthy person who decides to gain weight, and who sticks to his program of taking in more calories than he needs, and of spending as few as possible in needless physical activity, can be sure that sooner or later his efforts will meet with success. CALORIE TABLES FOOD MEASURES[4] CALORIES