A tax of around 70 pence per kilogram of sugar would "substantially reduce demand for sugar and sweets", lead people to lose an average 3.2 kilograms in weight, and lower the incidence of type 2 diabetes by 13%, according to a study.
A debate by health experts in the BMJ said the prevalence of coronary heart disease would also lessen, with these positive health effects being the greatest among poorer groups.
Sirpa Sarlio-Lahteenkorva, adjunct professor and ministerial adviser at the ministry of social affairs and health in Finland, quoted a 2011 study that concluded that a tax on sugar generally would be more effective than targeting specific food categories, such as a tax on sugary drinks as has been suggested by some health campaigners, with the British Medical Association (BMA) recently joining the call.
The food industry may find this more acceptable because it would treat all sources equally and it could also stimulate new products with less sugar, which would then be liable for less tax, she said.
She said taxes on alcohol and tobacco have been widely used for decades and reduce consumption, but food is a necessity and improving dietary habits this way is more complicated than limiting alcohol or tobacco use.
She wrote that in Finland there are excise duties on soft drinks, and introducing a sugar tax would be challenging, particularly for imported products.
"We need fiscal policies that take health seriously," she said.
"Sugary foods and sugar sweetened beverages are associated with weight gain. Governments must tackle the related adverse health effects, such as diabetes, coronary heart disease, and hypertension. A tax on sugar, preferably with measures that also target saturated fat and salt, and incentives for healthy eating, would help.
"The food industry argues that consumption taxes are ineffective, unfair, and damage the industry, leading to job losses; similar arguments are used by big tobacco. However, taxation of commodities such as alcohol, tobacco, and unhealthy food seems justified when the burden of ill health is mostly paid for by society."
Arguing against the idea, J T Winkler, emeritus professor of nutrition policy at London Metropolitan University, pointed out another study found that a 10% tax on soft drinks would reduce average daily intake by less than a sip, while another showed that a 20% tax would reduce consumption by just four calories a day.
He also highlighted out Denmark's "fat tax" was abolished just a year after being introduced following "universal opposition and widespread evasion".
He suggested that cutting product margins on soft drinks could be an effective alternative.
Companies add extra margins onto sugar-free drinks so that they always sell for the same price as the sugared alternative, he said.
Cutting part of that margin would create a price advantage for sugar-free drinks and "demand would shift, companies would make more money, and public health and private profit might for once push in the same direction".
Prof Winkler added: "Before and after the recent UK election, Government representatives—with candour rare among politicians—stated repeatedly that there will be no new food taxes and immediately rejected the BMA's proposal.
"Why are we still debating this idea? Nutrition policy needs price instruments but a more positive selection. Sugar taxes are unlikely to be adopted and would not make much difference if they were."