New Jersey, which has the highest percentage of overweight and obese children under age 5 in the United States, is escalating the battle against the bulge by starting a new agency to better coordinate programs to prevent obesity. It is believed to be the first in the country. According to a 2004 survey by the US Centers for Disease Control and Prevention, 17.7 percent of New Jersey children under age 5 are overweight or obese. Dr. Fred M. Jacobs, commissioner of the state Department of Health and Senior Services, said young people are a crucial target for the new Office of Nutrition and Fitness because it is easier to instill good diet and exercise habits to prevent obesity in the young than to reverse weight problems later; adults almost always gain back any weight they lose - and then some. Jacobs says he wants to tackle the obesity problem through education, support groups and encouraging physical activity, rather than by banning particular foods.