The study seeks to determine how many hazelnuts are required to reduce markers of heart disease, such as inflamed blood vessels, as well as cholesterol.
Human nutrition PhD student Agnes Tey had recruited more than 70 of the 100 subjects needed, but said she needed more men to balance the study.
Apart from a control group not eating hazelnuts, participants would be split in two groups, one eating 30g a day, another 60g a day, for three months.
Subjects must be clinically overweight and not on cardiovascular medication.
Supervisor Dr Rachel Brown said Miss Tey was "following the nut story" with her study, which was her second concerning the health benefits of hazelnuts.
The first, for Miss Tey's master's degree, examined whether the nut's health benefits were compromised by eating them ground rather than whole.
Miss Tey said she was focusing on hazelnuts because they were little studied compared with other nuts.
Hazelnut production in New Zealand had increased in recent years, as the nuts became more popular, she said.
