Diners order healthier items from the menu and consume fewer calories when they are in a well-lit room, according to a study in the Journal of Marketing Research.

The study found that diners in well-lit rooms were 16-24 per cent more likely to order healthy foods off a restaurant menu, when compared to diners in a dimly-lit eating space. Those in dimmer rooms also ate 39 per cent more calories in their meals, and were more likely to order dessert and fried foods, according to the study.

However, the study also found that diners in dimly-lit rooms made healthier choices when they were made more alert, either through instruction or caffeine placebos.

"We feel more alert in brighter rooms and therefore tend to make more healthful, forward-thinking decisions," lead study author Dipayan Biswas, of the University of South Florida, said in a news release.

The study was conducted by researchers from several U.S. universities, in collaboration with Roger Chacko, the chief marketing officer for the Carlson Rezidor Group of Hotels.

Researchers observed the dining habits of 160 restaurant customers at four casual chain locations, where customers were evenly divided up between well-lit and dimly-lit dining areas. Those in the better-lit rooms were more likely to order dishes with grilled or baked fish, vegetables and white meat, while those in dimly-lit rooms were more inclined toward fried foods and sweets.

However, dining in the dark does have its advantages. "Dim lighting isn't all that bad," study co-author Brian Wansink, of Cornell University, said in a news release. "Despite ordering less-health foods, you actually end up eating slower, eating less and enjoying the food more."