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According to the American Association for Marriage and Family Therapy, national surveys have shown that 15 percent of women and 25 percent of men have had a full-blown affair outside of their long-term relationship — a number that jumps by 20 percent for each sex when expanded to include emotional affairs.

When you think of a cheating partner, you may picture a bar or a nightclub. But that’s actually not one of the top places people meet their affair partners, Debra Macleod, a marriage expert and author of books including “Couples in Crisis: Overcoming Affairs & Opposite-Sex Friendships,” told Fox News.

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Macleod interviewed more than 300 couples over the last year to figure out where most of them had met their affair partners. Fox News spoke to Macleod, along with Dr. Jane Greer, New York-based marriage and sex therapist and author of “How Could You Do This to Me? Learning to Trust After Betrayal,” about the top places and just why many budding affairs start there:

1. In the office
The workplace is traditionally the place where people have the most affairs, Macleod said. When we go to work in the morning, our makeup and hair is fresh, and we’re typically on our best behavior, she explained.

Greer agreed, noting that the shared creative energy, goals, and passion about projects leaves people more receptive than usual to somebody’s interest or admiration.

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2. At the gym
When you’re at the gym, you’re already displaying your body: “There’s a whole element of physical attraction, availability and accessibility,” Greer explained.

A common type of affair that Macleod encountered was one between clients and personal trainers. A woman may feel not only physically close to a trainer as she works out with him, but emotionally close as he supports her, Macleod said.

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3. On social media
People tend to reconnect with old flames via social media, Macleod said, noting that it’s easy for them to reminisce about the “good old days,” when they were younger and not bogged down by so many responsibilities. They may start to fantasize with one another what their lives could be like if they had stayed together, which can quickly snowball into a deeper intimacy, she said.

4. Through a social circle
Proximity is key: People often find affair partners through existing social circles, such as a couple they are friends with. That’s because they are already close and familiar with those people, Macleod explained.

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5. At a volunteering gig
People may bond over a common cause while volunteering, Macleod said. Greer agreed, noting that anytime you’re working toward a common cause or objective, you may start to feel a sort of energy that leaves you more vulnerable to this attraction.

6. In church
Church can create a false sense of intimacy between members, or between a leader and a member, Macleod said. People may open up about their marriage problems, looking for comfort, not realizing that others may take advantage of that vulnerability or else develop feelings for that person.