Since America is the land of opportunity, and nothing that interests more than six people fails to generate an industry, food is big business here, and so is dieting. First we glut, then, in a passion of guilt, deny ourselves the joy of our gluttony."" A funny, serious business altogether, and prime fodder for Chris Chase. From the Julia Child TV phenomenon (and the French-cooking craze it triggered) to the fruit-laden program of Nathan Pritikin, from Mimi Sheraton's ""exposure"" of John McPhee's genius-chef ""Otto"" to the gains and losses of pizzaking Larry Goldberg, Chase pokes around, asks questions, draws conclusions, makes discoveries. Fast food has been much maligned: Consumers Reports even found that a typical entree, plus fries and a shake, provides about a third of required daily nutrients. And there may be a fat backlash underway: witness the success of a magazine called Great Big Beautiful Woman and the National Association of Fat Americans' stint on 60 Minutes (notwithstanding ""the real melancholy"" that Mike Wallace claimed to have detected). The sweep is all-encompassing: cookbooks and cooking schools, diet spas and diet pills, food processors and convenience foods. Complete, in each case, to historical background and consumer response. For some readers, too much may be made of the New York restaurant-reviewing/gourmet-parrying scene; some may be put off by Chase's addiction to puffs (""The shape of your genes helps determine the shape of your jeans""; Jackie Onnassis' ""Annemarie was a peach, and like many a peach before her, she was canned""). But it's all bright and lively and precisely aimed.