The University of Glasgow researchers said refresher courses would boost the effects further.
The study looked at courses lasting between four and eight weeks for parents of pre-school children.
Classes included information on budgeting, nutrition and cooking simple meals.
Questionnaires filled in immediately after the courses showed an immediate boost in participants' confidence in cooking, preparing and trying new foods.
A year later, 44 of 100 cookery class attendees agreed to be interviewed again and researchers found there was still a significant increase in their confidence in following simple recipes and using basic ingredients.
They also found that participants were eating fewer ready meals than before the courses, and were eating portions of fruit and vegetables daily compared with just a few times a week before.
Study leader Dr Ada Garcia said that, although the study numbers were small due to difficulties in re-contacting people after a year, the results showed that such programmes had a measurable effect on people's diets.
The study has been published in the journal Public Health Nutrition.