A study of 2,000 adults found they each have an average of two secrets, with the number of partners they have had, smoking, hygiene habits and secret spending also featuring in the top 25 list.
But worryingly, mental health issues are the most common secret being kept from others, followed by an cringeworthy incident they would rather forget.
A third keep things to themselves to avoid embarrassment, but nearly one in five are keen to avoid any relationship issues.
Nearly one in five (18 per cent) also keep quiet to protect their personal reputation, while just over one in 10 have done so to avoid getting into trouble with the police.
A spokesman for Sky HISTORY, which commissioned the research to launch its new series of shows, Summer of Secrets, said: “The research suggests that the British public keep many secrets from each other, whether that’s something trivial, embarrassing, or even personal – like mental health.”
The study also found one in five Brits (20 per cent) are most likely to keep a secret from their mothers, while 16 per cent won’t even tell their deepest secret to a friend.
Another 16 per cent will keep things from their partners, with 14 per cent admitting they dread their other half discovering the truth.
More than one in 10 (13 per cent) would even keep a huge lottery win to themselves rather than sharing the news with their loved one.
However, the study carried out via OnePoll, found keeping hold of a secret can have both a physical and mental impact with more than a quarter of adults admitting it impacts their day-to-day decision making.
The spokesman for Sky HISTORY, added: “This research has given some insights into how prevalent secrets are in society today.
“Part of the reason why secrets are interesting is our desire to know what they are and why they’re being kept.
“This July, the channel has dedicated a season of programming to uncovering secrets from a range of subjects – everything from UFOs and stories of long-lost cities to the real stories behind comic books and America’s hidden history.”
Summer of Secrets begins on Monday 12th July at 9pm with Curse of the Lost Amazon Gold.
TOP 25 SECRETS KEPT FROM FAMILY AND FRIENDS
1. Your mental health
2. An embarrassing incident
3. Your internet history
4. Eating / snack habits
5. Hygiene habits
6. How many partners you’ve previously had
7. Bank /credit card statements
8. That you have faked an illness to get out of commitments
9. Having an affair
10. Having a one-night stand
11. An illness or condition
12. Smoking habits
13. That you have faked an illness to get out of work
14. How much you spend on food
15. Your phobias
16. Supporting a football team your friends don’t like
17. How much time you spent in the pub
18. Buying expensive items online
19. Drug use
20. Alcohol abuse
21. Having a celebrity crush
22. How good you are, or aren’t at something
23. Being on a diet
24. Political opinions
25. Your family history