Scientists who assessed the emotional feelings, body language and heart rate of female volunteers found EL James' bondage blockbuster was less enjoyable than a cookery book by celebrity chef Jamie Oliver.
The test was part of an experiment designed to see what really makes a good read when all the marketing hype is stripped away.
Extracts from different genres of books, including thrillers, romantic fiction, sci-fi, non-fiction and erotica, were read by the 50 participants, who had an average age of 35.
The most enjoyable genre proved to be "romantic suspense", with a "positive engagement" score of 83pc.
In contrast, Fifty Shades Of Grey, representing erotica, produced the lowest score of 52pc and was trumped by Jamie Oliver's 30 Minute Meals (55pc).
"This experiment finally answers the long-debated question about whether to trust your heart or your head, with heart prevailing when choosing the perfect summer read," said consultant behavioural psychologist Jo Hemmings, who devised the tests.
Pulse rate was also measured to provide an indication of stress and anxiety.
Participants were also asked to answer questions about their emotional reaction to what they had read.
Romantic suspense came top of the "most enjoyable" genre list with a score of 83pc.
This was followed by thriller (74pc), sci-fi and fantasy (60pc), non-fiction (55pc) and romance/erotica (52pc).