The idea that low-carb could be a healthy choice of booze is a "big fat myth", according to a new study.

The study - undertaken by Cancer Council Victoria and public health group LiveLighter - found most low-carb beers had a similar amount of carbohydrates and kilojoules as regular beer.

Campaign manager and dietitian at LiveLighter Alison McAleese said marketing certain beers as low-carb is "doing nothing more than giving these beers a false healthy halo".

"They're not healthy and drinking them certainly won't prevent weight gain."

On average, a typical lager or ale has just 1.4 grams of carbohydrates per 100ml, while low carb Pure Blonde has just over 0.5 grams and lower carb Carlton Dry actually has 1.9 grams.

Alcohol, not carbohydrates, doing damage

Ms McAleese stressed most beers are already relatively low in carbohydrates, and it's actually the alcohol, not carbs, making beer so high in kilojoules.

"Around 80 per cent of the kilojoules in a typical beer come from the alcohol itself, while only around 15 per cent come from carbohydrates and less than one per cent from sugar,” Ms McAleese said.

"At the end of the day it's the alcohol in beer, not the carbohydrates, that does the damage to your waistline and puts you at greater risks of serious health problems, including cancer."

This led the groups to call low-carb beer a "big fat myth" and ask the Federal Government to make nutrition labelling mandatory on all alcohol products.

Ms McAleese said the best way to avoid weight gain and reduce health risks was "to choose lower alcohol beer and cut back".

The study found that there was significant misunderstanding around low-carb beer.

"More than one in three men (35 per cent) incorrectly think low-carb beer is healthy (while) one in five (22 per cent) women also mistakenly think low-carb beer is a healthy option."

Cancer risk

Head of Prevention at Cancer Council Victoria Craig Sinclair also said that if kilojoule reduction was the goal, people were better off "choosing lower alcohol beer or, better yet, cutting back on the amount of alcohol they are drinking".

"The unwanted weight gain from the empty kilojoules in beer can lead to obesity, which increases the risk of 13 types of cancer, type 2 diabetes, heart and kidney disease, and stroke," Mr Sinclair said.

"But it gets worse. Alcohol is also a known cause of cancer and has been recognised by the World Health Organisation as a Group 1 carcinogen - the highest classification available ... The more alcohol you drink, the greater your risk of cancer."

He recommended no more than two standard drinks on any day and to avoid binge drinking, which is drinking of more than four standard drinks in a sitting.

Responding to the study, Carlton United Breweries (CUB) told ABC News that nutritional information about Pure Blonde was displayed on the label "as we know this is important to Pure Blonde consumers", and nutritional information for all the company's beers was available online.

"CUB uses a brewing process for our low carbohydrate beer that utilises an enzyme that breaks down residual carbohydrates in the beer," it said.

"Beer is a great beverage, that like most foods and drinks should of course be enjoyed in moderation."