"By instituting a 20 percent tax... it is predicted to reduce energy intake by about 36 kilojoules per day, resulting in a 3.8 percent reduction in obesity in men and a 2.4 percent reduction in obesity in women," researcher Mercy Manyema said in a statement on Wednesday.
This translated to a decrease of more than 220,000 obese adults in South Africa.
Manyema said it was the responsibility of government to protect the health of its population.
"One way of doing so is through nudging people to make healthier and more sustainable choices. An SSBs tax has the potential to do this in addressing obesity-related diseases," said Manyema.
Research was carried out by academics from the university, and it was published in an open-access journal "Plos One" on Tuesday.
The paper measured the effect of a tax on SSBs on the prevalence of obesity among adults in South Africa.
It found that taxing SSBs could impact the problem of obesity in the country, particularly in young adults.
The academics said South Africans had become more obese over the past 30 years, and the country was presently considered the most obese country in sub-Saharan Africa.
Over half of South Africa's adults were overweight or obese -- 42 percent of women and 13 percent of men.
"While SSBs alone may not be the only reason for an increase in body fat, these fizzy drinks do not contain any essential nutrients, have a high sugar content and a strong link to weight gain," said senior author of the paper, Professor Karen Hofman.
"Drinking just one SSB a day increases the likelihood of being overweight by 27 percent for adults and 55 percent for children."
The paper follows a recommendation by Health Minister Aaron Motsoaledi on the need to regulate foods high in sugar to address obesity and its related diseases.