Consistently eight out of ten U.S. adults describe themselves as “extremely healthy” or “very healthy,” but only one-in-five adults have what is considered to be a “most healthy” diet and 65% of adults’ body mass index (BMI) is overweight or obese, according to The NPD Group, a leading market research company. In spite of their overly positive assessment of their own health, almost half of all U.S. adults (104 million) recognize the need to change their diet in order to improve the overall healthfulness of their lives, a recently released NPD food and beverage market study finds.

U.S. adults define healthy eating in terms of adding to or taking something out of their diets differently, according to NPD’s The Market for Functional Foods report. Fifty-five percent of the 1,921 adults NPD surveyed said that eating healthy is equally adding to and taking out of their diet. Of the remaining adults surveyed, 26% said that “adding something to the diet” is healthy eating, and 19% said that “taking something out” of the diet is.

Dieting, which is traditionally more about taking something out of the diet, is not the health or weight management solution it once was for U.S. adults, NPD reports. In the year ending December 2011, 21% of adults claimed to be on a diet down from the 24% who claimed to be on a diet in 2004. As for adding something to a diet, U.S. adults and kids turn to an easier solution like taking vitamins, according to The Market for Functional Foods report findings.  Vitamin supplement usage is on the rise among both kids and adults. Another way in which U.S. consumers are adding something to their diets is with functional foods and beverages, which are products that offer additional, pro-active health benefits beyond basic nutrition, like fortified with whole grains or probiotics. One-third of adults, almost 80 million, indicate strong interest in functional foods and beverages, and one-in-four adults are already using a functional food or beverage at least once a day.

“A huge opportunity exists to increase functional product usage among adults, and teens, who have already tried functional products at some point but are not using them on a daily basis,” said Darren Seifer, NPD food and beverage industry analyst. “If the 118 million less frequent adult users could be encouraged to include just one more functional food or beverage into their diet each week, this would result in an increase of over 6 billion eatings each year.”