LYON, France — I met David on my first of four days visiting Lyon. From our first kiss that night, we started behaving like a couple: We had difficult conversations, we were finishing each other’s sentences and the sex was intense and intimate. On the third day, I accidentally told him my darkest secrets, which I had never admitted to any man before. Instead of being scared off, he held me and wiped my tears with his thumb. On our final night together, he told me he loved me.

“I know I’m not supposed to say it so soon, and I don’t want you to say it back,” he said. “But . . . I do.”

There was no way I was saying those words back. I liked him, sure. But love? You can’t love someone you barely know, right? Then again, I’d never been in love-love. Maybe I’m a cynical American woman who put too much weight on this word.

Now that I live in France full time, I’ve found that professing one’s love right out of the gate is not aberration. It’s just one of the many cultural differences: The French go all in from the start. But in the United States, where I lived for 39 years before moving to Europe, dating is generally casual and cautious. Professing your love early on — or immediately treating someone like your boyfriend or girlfriend — generally comes across as needy, aggressive or sociopathic.

David didn’t seem to be any of those things. Just sweet, romantic, unafraid. So I went with it. I’d probably never see him again, I figured.

We dated long-distance for almost a year.

Since then, I’ve met many American women and expatriates who have quickly landed in relationships with French men. And most of us have found it pretty confusing.

The first day American business owner Kelly Clark arrived here, she hit it off with a Frenchman. After a couple of days together, he sent her a Facebook message to say he had booked a flight to Barcelona to join her on the next leg of her trip. She was surprised rather than annoyed by this grand gesture, because there were language barriers. He may have assumed she wanted him to join her because she had told him the specifics of her travel plans, she says. After they returned to France, she invited him to join her for a week in Venice.

“I thought that we were just hooking up on vacation, having a summer fling, skinny-dipping-and-drinking-spritz kind of thing. I didn’t find out that to him we were ‘dating’ until about a month into our relationship,” she said, “after sort of stumbling into the conversation where I was interested in putting a definition on it.” At first she was surprised by his commitment. “It was far from what I was used to, and I was delighted by it. I found it to be a very … ‘swept off my feet romance,’ which knows no borders or boundaries.”

Like me and several American women I’ve met, Clark was used to dating American men who were skittish about labeling anything until a few months have elapsed. Hooking up seldom meant you were suddenly in a relationship. But to her current boyfriend, it meant they were official.

For the first six months of our relationship, David and I had several fights over the phone about exactly this. I didn’t necessarily want to sleep with anyone else, but he was in France and I was in Spain, so it seemed impractical to have an exclusive long-distance relationship with someone I’d only spent four days with.

Plus, my history of trysts or one-night stands in America was much like Clark’s — they never led to anything serious. David just couldn’t comprehend why being exclusive was such a big deal, or why this American girl he loved was obsessed with the notion of freedom. It took me six months to finally agree to be exclusive, and that’s only because another woman was trying to move in on him.

Like me, Clark did a year of long distance before moving to France. She and her beau talked every day on FaceTime and frequently traveled to see each other. “It was an intense experience,” she said, “which I have trouble imagining an American guy doing.”

Nine years later, they are still going strong.

Cathline Fermet-Quinet, a French psychologist and sexologist in Lyon, confirmed that, yes, dating in France is different. “We don’t have this causal dating period when it’s okay to date several people at the same time and keep your options open,” she said. “Things end up going faster because we’re all in. It’s pretty common to go on three or four dates a week with someone you just met.”

Meeting friends usually happens after a few dates, she said, and meeting the parents within one to three months.

Caroline Conner, an American who runs wine tastings in Lyon, has had similar experiences. “American men will do anything to avoid calling you their girlfriend. For some reason that’s terrifying to them,” she joked. “But French men seem to want girlfriends. If you have sex once or even just make out — Bam! You’re together!”

The only exception, she said, seems to be if you meet on a dating app and discuss being “sex friends.”

This all-in approach isn’t always smart, Fermet-Quinet said. “Signing a contract too early and under the influence of love hormones is a little risky.” She said she believes couples who dive right in don’t stop and ask themselves whether they share the same vision of love or whether they are even compatible.

Emily Chavez, an American law student here, said the accelerated approach the French take to dating hasn’t always ended well for her. One man admitted the morning after they hooked up that his recent breakup was not actually a breakup. Others have pretended to be okay with a relationship — or at least not contradicted her when she said that’s what she was looking for — only to admit a few weeks later, when things were really starting to get heavy, that they didn’t want anything serious.

“Now that I’ve dated a few, I have decided that the easiest thing is just for me to go with the flow until things go sour,” Chavez said.

According to Fermet-Quinet, one-night stands aren’t as common in France, or they don’t seem like one-night stands because people are too polite to cut off contact without a discussion. Unless you’ve discussed being “sex friends,” not calling or texting someone back after a night together is disrespectful, even if you don’t want to go any further.

As much as I like being treated with respect and care, it can be quite confusing. Nina Coates, a British yoga instructor in Lyon, agreed. “They treat you with too much respect for someone who just wants to shag,” Coates said. Like me, she’s open to relationships or “sex friends,” but we never know what we’re getting ourselves into.

The last two men Coates tried dating both disappeared after going “full boyfriend.”

“They text you every day: Before they go to sleep, as soon as they wake up, when they get home from work, when they’re out with friends. It’s constant,” she said.

Both guys corrected her French homework, and one even helped her find a used bicycle online, making all the calls in French for her. “They cook you dinner, show you pics of their mom, cuddle on the couch, listen when you speak and ask you thoughtful questions. They’re good guys … but they don’t know how to not be too boyfriend,” she said.

Although we both enjoy the romantic gestures and being treated like cherished human beings, it stings much more when they disappear. Neither of us has a clue who wants to date and who is just grooming us for a sexual friendship because they act the same regardless.

Even the ones who do want relationships can backtrack abruptly. David and I ended things right before I moved to France. Even though I was the one to drag my feet on the girlfriend label, he was the one who wasn’t truly ready to be a boyfriend.

Dating in the country known for love may be exciting and romantic, but it can also make you even more cynical and cautious about dating than back home. Because in the United States, when someone finally does say “I love you” and goes “full boyfriend,” you actually believe them.