The humble grapefruit is set for a makeover this summer, as growers look to reverse declining sales and shed the fruit's outdated image with a campaign that will suggest eating it can make people feel more energetic and attractive.

As part of the campaign, consumers will be encouraged to eat one grapefruit a day to boost their wellbeing. A new website, www.sagrapefruitchallenge.com, will support the initiative by highlighting the health benefits associated with eating grapefruit regularly.

The move comes in the wake of consumer research by the Citrus Growers' Association of Southern Africa showing a marked improvement in people's perception of their health and appearance after eating grapefruit. Of the 65 women asked to eat a grapefruit a day for 14 days, 80% said their concentration was excellent or very good after the fortnight compared with 38.4% prior. Similarly, 67.7% rated their energy levels as excellent, compared with 18.4% beforehand.

Participants also reported that their appearance had improved, with 81.6% saying their hair had got better over the two-week period, 58.5% saying they had lost weight and 70.8% saying they felt more comfortable with their body.

Once a popular diet food, sales of grapefruit have declined over recent years. In the 52 weeks to 20 March, grapefruit volume sales fell 3.6% to 27,492 tonnes [Kantar Worldpanel].

The downward trend has been attributed to the bitter taste of white grapefruit and people's unwillingness to add sugar. However, many varieties are less bitter, a fact highlighted on the new Grapefruit Challenge website.

"Modern varieties of grapefruit from South Africa are naturally sweeter there's no need to add sugar. Try red and pink varieties," the site says. It also hosts instruction videos, fronted by chef Sophie Michell, on how to prepare a grapefruit for salads.

The majority of grapefruit in the UK comes from South Africa and Swaziland, with South Africa exporting 13,800 tonnes to the UK last year.