Enjoying an iced coffee drink? Better skip dinner or hit the gym afterwards, with a cancer charity warning that some iced coffee drinks contain as many calories as a hot dinner.

The World Cancer Research Fund conducted a survey of iced coffee drinks sold by some popular chains in Britain including Starbucks, Caffe Nero and Costa Coffee to gauge the calories as studies increasingly link obesity with cancer.

The worst offender — a venti dark berry mocha frappuccino from Starbucks — had 561 calories. Other iced coffee drinks contained more than 450 calories and the majority had in excess of 200.

Health experts advise that the average woman should consume about 2,000 calories a day and a man about 2,500 calories to maintain a healthy weight. Dieters aim for 1,000 to 1,500 calories a day.

"The fact that there is an iced coffee drink on the market with over a quarter of a woman's daily calories allowance is alarming," Dr. Rachel Thompson, science program manager at London-based WCRF, said in a widely-reported statement.

"This is the amount of calories you might expect to have in an evening meal, not in a drink."

The WCRF has estimated that 19,000 cancers a year in Britain could be prevented if people lost their excess weight with growing evidence that excess body fat increases the risk of various cancers.

Thompson said having an iced coffee drink as an occasional treat was fine, but it was best to opt for an unsweetened coffee with skimmed or semi skimmed milk — and steer clear of the cream or sugary fruit syrups.

"If you are having them regularly then they will increase the chances of you becoming overweight, which in turn increases your risk of developing cancer, as well as other diseases such as heart disease and diabetes," she added.

The WCRF, which identified the drinks' calories, did note that healthier versions of iced coffee drinks were available at all the stores.

Starbucks in 2007 changed its default milk used in beverages like lattes to 2 percent from whole milk and is this year testing a frappuccino formula that mirrors its bid to cut calories in its food items to offer healthier choices.

Starbucks did not immediately return phone calls or an e-mail Monday morning.

Costa Coffee on its Web site gives full details of the contents of its drinks and food items, stressing that drinks can be made as asked with skimmed, full fat or soya milk.

Caffe Nero also publishes the calorie contents of all its drinks and food on its Web site.

Reuters contributed to this report.