By analysing the amount of oxygen and carbon dioxide the walkers breathed out, the researchers were able to work out how much fat they were burning.
After seven days of taking the supplement, fat oxidation had increased by 10 percent.
That jumped to 16 percent after week two. Meanwhile, the group average of all those who responded to the supplement was 27 percent.
Professor Willems added: “This isn’t an in-your-face difference from week one to week two, but the fact that we have shown an increase from 10 percent to 16 percent between the two relatively short time points is encouraging.
“Blackcurrant clearly favours fat as fuel and taking it every day is more beneficial.
“This study adds to growing evidence that New Zealand blackcurrant is beneficial for health purposes when combined with exercise and taken every day.
“It’s a fairly unique for a natural product and a berry to achieve these levels of increases in such a short space of time.”