Sex is important in any relationship, and we strive to constantly improve our sex lives even though it's already good. But sometimes it's the small things that make all the difference in the bedroom.

Here are some surprising things that that can affect your libido:

His waistline
He's with you, he's happy, and so is his appetite. He's growing with you - sideways. But guess what, that extra weight may actually be great for your sex life. Fat men last longer in bed, according to a study published in The International Journal of Impotence Research showing that men with higher body mass could make love for more than seven minutes on average, versus less than two for their fitter and slimmer peers. Body fat may also protect against premature ejaculation because it contains higher levels of the sex hormone estradiol, which slows down a man's ability to ejaculate. However, levels that are too high may lead to erectile dysfunction, a condition more common in obese men.

Your sex toys
Some sex toys contain dangerously high concentrations of phthalates, which are industrial chemicals that make plastic soft, squishy, and easily molded into bumps, ridges and pearls. Phthalate exposure is associated with serious health problems, including lower testosterone levels, lower sperm counts and even certain cancers. It's best that you use safer materials such as medical-grade silicone, glass, metal and wood, or use a condom over your rubber toy if you think it has phthalates.

Cold feet
Seriously and literally: An orgasm study at the University of Groningen found that half the couples were unable to climax due to cold feet. Once socks were offered, the success rate shot up to 80 percent. Comfort was key, and the area of the brain associated with genital sensation is next to the one associated with feeling in the feet.

Bad smells
Any foul odor (from the restroom, kitchen, your rubbish bin) primes your subconscious to protect yourself. According to a finding from the University of New Mexico, men and women sitting in a room that smelled reported a significantly greater intention to use condoms than those in a normal-smelling room. An innate disease-avoidance mechanism kicks in, which isn't completely a bad thing since it leads to fewer STIs and unplanned pregnancies.

Which sibling are you?
A study at Florida Atlantic University found that firstborns desire fewer sex partners on average, than their younger siblings. In general, firstborns focus on long-term goals like having kids earlier in life, while younger siblings tend to pursue short-term sexual strategies. The explanation is that eldest siblings identify more with their parents and the status-quo norms.

Bike riding
Women who ride a racing-style bike with handlebars lower than the saddle for more than 10 miles weekly have a serious problem: a sustained loss of feeling in their genitals. WTF. A study at Texas A&M Health Science Center says the forward-leaning position puts undue pressure on the soft tissues of the perineum and pelvic floor.

Dental hygiene
Men who have bad dental hygiene have a few things to worry about. Bad breath is one thing that can affect his sex life. Also, a study published in the Journal of Sexual Medicine says those with gum disease (a common result of dental neglect) are more than three times more likely to have erectile dysfunction than those with healthier mouths. Unflossed gums harbor bacteria that can enter the bloodstream, which clogs blood vessels, which in turn reduces blood supply to the penis.