There are those who claim beer is fattening and the dreaded beer belly is proof of that. Then there's those who claim that beer contains no fat so it can't be fattening.

Then there's the camp that says it's not beer but the food you eat while drinking that's to blame.

Then there's the growing market in low and no-carb beers, which would seem to suggest you can drink more and keep the weight off.

The British Beer and Pub Association even brought out research that a glass of beer has less calories than a similar measure of fruit juice or milk. This may well be true, but how often are you going to drink six schooners of milk?

University of Wollongong Smart Foods Centre research dietitian Beck Thorne says it's a bit simplistic to ask if beer is fattening. What you need to do is consider your whole diet, not just one small part of it.

"It's all to do with calories in and calories out," Thorne says.

"Anything in excess, if you don't use it, you're going to store it."

As for the beer versus milk argument, Thorne points out the differing nutrient value in the two drinks. Milk has calcium and protein while beer "doesn't have any nutrient benefits".

While too much beer can cause weight gain, there's also a link between alcohol and eating.

"What happens when you drink alcohol is you actually decrease your inhibition to eat, so you're more likely to want to eat when you drink alcohol," Thorne says.

"The issue is usually the environment you're drinking in. If you're out consuming alcoholic beverages such as beer you might be in a pub, so what kind of food is available at a pub? It might be potato chips over the bar. If you're out with mates it could be going past the kebab shop."

It also turns out that beer - like alcohol in general - has no fat but it's not just fat that causes you to put on fat. Alcohol also contains more kilojoules per gram than either protein or carbohydrate.

In the end, Thorne quotes National Health and Medical Research Council guidelines recommending a limit of two standard drinks a day and no more than four on any one occasion. Couple that with Heart Foundation advice to go alcohol-free at least two days a week.

Thorne says carbohydrate modified beers are lower in calories, but people should still stick with the two standard drinks measure, which is actually less than you might think.

"For instance, a schooner of regular beer at a pub, which is 425ml, is 1.6 standard drinks.

"If you bought a six-pack of beer in bottles, one of those beers is 1.4 standard drinks," Thorne says.

"... if you've had two schooners, you've actually had three standard drinks."