The effectiveness of two persuasive techniques in changing the nutrition knowledge, attitudes, food behavior, and dietary intentions of adults was compared using a pretest-posttest experimental design. Short written nutrition brochures were used to convey either a threat appeal, which emphasized the harmful effects of not following recommendations made in the brochures, or an optimistic appeal, which emphasized the benefits to be gained if these recommendations were followed. All brochures recommended consumption of nutrient dense, i.e., high nutrient, low calorie, foods as a way to either avoid the threat or accrue the benefits of the conditions described.

A random sample of 1,500 adults was drawn and assigned to the control group or one of two experimental groups:​ the threat appeal group or the optimistic appeal group. The study was carried out through the mail. All respondents completed the pre- and posttest questionnaires, but only the experimental groups received the brochures. Variables assessed by the questionnaires included:​ (a) respondents' nutrition knowledge, (b) attitudes toward nutrient dense foods and learning more about nutrition, (c) dietary habits, (d) dietary intentions, and (e) demographic characteristics. Food behavior was examined using a food coupon system. Respondents selected two foods from a list of 15 for which they desired $0.40 "cents-off" coupons. Respondents in all groups received coupons for completing the pre- and post-test questionnaires;​ experimental group respondents also received coupons for reading the brochures.

About one-third, or 450 individuals, of those who received the pretest agreed to participate in the study. The subsequent return of brochures and posttests was between 85 and 90 percent. Demographic characteristics of the respondents, and the prescores on knowledge, attitude, food behavior, and dietary habit instruments did not differ significantly among groups. The respondents were primarily middle-aged females of average socioeconomic status and middle-to-high educational level.

The experimental groups' postscores on the knowledge and "Nutrient Dense Foods" attitude scale were significantly higher than the control group when adjusted for differences in prescores, but these postscores did not differ significantly between the experimental groups. The same finding occurred when scores on the dietary intention items assessing use of skim milk and general intentions to change the diet were compared. The postscores on the "Learn More About Nutrition" attitude scale, food behavior, and all the other dietary intention items did not, however, differ significantly among groups.

Older respondents had lower scores than younger ones on both the knowledge pre- and posttest;​ but they had higher food behavior scores than younger ones at pre- and posttest time, and also scored higher on the habit/intention item concerning use of skim or "two-percent" milk. Respondents scoring higher on the "Learn More About Nutrition" scale at pre- and posttest time also scored higher on the "Nutrient Dense Foods" scale at both times, and vice versa. Scores on both attitude scales were also positively related to the habit/intention item concerning use of fruit or juice as snacks. In addition, those with higher "Learn More About Nutrition" attitude scores were more likely to report habitual use and future Intentions to consume milk or juice rather than soft drinks.

Respondents with higher pre- and posttest knowledge scores had significantly higher food behavior and "Nutrient Dense Foods" attitude scale pre- and postscores, and also reported more habitual use and stronger intentions to use fruit canned in juice or light syrup. Females reported more frequent use and stronger intentions to use plain canned or frozen vegetables than did males.

Both the threat and optimistic appeal approach appeared equally effective in influencing changes in nutrition knowledge and an attitude specifically related to the content of the brochures, namely, "Nutrient Dense Foods." Neither was successful in changing food behavior and a more general nutrition attitude, "Learn More About Nutrition."