Peter had never felt particularly interested in sex. Although he’d had various opportunities throughout his adult life, he had always been surprised at how lacklustre his attitude to these sexual encounters was. Maybe he was tired, he’d drunk too much alcohol, or he was worried about his performance – whatever it was, it hadn’t been a major worry until he met his current partner four years ago.

“For her, that physical connection with men had always been a big thing,” he says. “I wasn’t interested in it to the same level, and this still creates issues in terms of what the other perceives should be the right amount.”

Peter’s low sex drive is by no means unusual. Up to 10% of men and women are affected by hypoactive sexual desire disorder (HSDD) – defined as a continued lack of interest in sexual activities and fantasies, resulting in personal distress. In our highly sexualised society, people with low libidos can feel irreparably broken – yet scientists are increasingly realising that desire is neither fixed, nor a simple on-off switch in people’s underpants. Rather, it is a product of competing systems in the brain – and the key to boosting it may lie in redressing the balance between these inputs.

Most people assume that sexual response is linear: if you’re attracted to someone, and they say or do the right things, this will inevitably lead to arousal then intercourse. However, this model fails to account for people’s background levels of desire – their hunger for sex.

In the late 1990s, researchers at the Kinsey Institute in Bloomington, Indiana, proposed a different scenario, known as the dual control model. It likens human sexual response to an accelerator and brake pedal in a car. The accelerator responds to all the sex-related sensations, thoughts and feelings a person is experiencing, and sends a “turn on” signal to the rest of the body, while the brake notices all the reasons not to be turned on, which it codes as potential threats, and sends a “turn off” signal.

“The key thing about this dual control model is it proposes that people vary in their propensity for excitation or inhibition,” says Dr Cynthia Graham, a senior scientist at the Kinsey Institute. So, some people have very sensitive accelerators and find it easy to get turned on; others have sensitive brakes, which can override these signals – and some have both a sticky accelerator and a sensitive brake.

Contextual factors, such as stress, anxiety about being interrupted, or how you’re feeling about your partner or body, can apply further pressure to that brake.

“The process of becoming aroused is the dual process of turning on the ons, and more importantly, turning off the offs,” says Emily Nagoski, a sex educator and author of Come as You Are. “Sometimes when people are struggling, it’s because there’s not enough stimulation to the accelerator – but more often it’s because there’s too much stimulation to the brake.”

For now, the most effective approach to boosting a flagging libido is psychological: Nagoski advises thinking back to past sexual encounters where you found it easy to become aroused, as well as ones that started out well before something killed the mood. The idea is to identify cues from your environment, emotions and experiences that activate your accelerator and brake, and then have a discussion with your partner about how to do more of the accelerator things, and less of the brake things.

But what if there were a drug that could achieve a similar thing? Although the dual control model doesn’t specify the brain regions involved, recent advances in brain imaging have shed further light on what might be happening in individuals with HSDD, like Peter.

“The basic theory of why this disorder comes about is that there is an excess of activity in those brain areas that are related to self-monitoring and introspection – thoughts such as: ‘How am I performing?’ ‘How do I look?’ ‘What’s my partner thinking?’ – and these are basically suppressing the downstream, more primal sexual arousal and desire activities,” says Dr Alexander Comninos, an endocrinologist at Imperial College London.

Recent studies have suggested that a naturally occurring hormone called kisspeptin might help to override some of these introspective activities, and boost the brain’s responses to sexually relevant cues, such as the way someone smells. But no one had ever tried giving kisspeptin to people with low sexual desire. So Comninos and his colleagues launched two trials in men and women with HSDD.

Peter was one of those who volunteered. On two separate occasions, he lay in an MRI scanner with his penis strapped to a sensor that measured its girth, while erotic content played on a screen in front of him. During one of these visits, he was injected with kisspeptin, and on the other he received a placebo injection.

“There was no kind of magic transformation – nothing that would make you say ‘Ah, this must be it’,” says Peter.

Even so, brain scans from trial participants suggested that kisspeptin dampened activity in brain regions linked to HSDD, and boosted activity in areas that respond to sexual cues. Among male participants, penile rigidity also increased by up to 56% while watching erotic content after receiving the kisspeptin – and both men and women reported feeling slightly sexier after administration of the drug.

Comninos cautions that more studies are needed – including testing people in more natural settings, such as the bedroom – before concluding that kisspeptin boosts sexual desire.

Even if it does, Nagoski says she’d be cautious of any drug that overrides the brain’s response to potential threats. She points out that low sexual desire isn’t necessarily a problem: “When your brakes are on that’s your brain responding the best way it can to make sure you are safe.”

Better would be to forget about desire, and concentrate on identifying and removing those factors that are making it difficult for someone’s brain to access pleasure. “Any programme that is focused on desire is sort of inherently missing the point,” says Nagoski. “Desire is not predictive of having a satisfying sex life, particularly not in a long-term relationship. It is pleasure that makes a difference.” For Peter, participation in the kisspeptin trial may have achieved both goals. Within a couple of days of what he believes was the kisspeptin infusion, he was intimate with his partner – an encounter that resulted in her becoming pregnant with their son. Since then, he says their sexual relationship has improved, and they are now expecting their second baby.

Possibly, the kisspeptin infusion triggered some kind of lasting change in his brain – although Peter accepts this is unlikely. More plausibly, his involvement in the trial, and conversations about it, have subtly altered his attitude to sex. Either way, the result has been “life-changing”, he says.

How do other factors affect libido?

Sleep
Unsurprisingly, getting more sleep can have a measurable impact on a person’s interest in sex, because they are less likely to feel overwhelmed and exhausted. University of Michigan researchers found that when women in relationships slept for an extra hour, they reported higher levels of desire and were 14% more likely to have sex with their partner the next day.

A new location
For some people, having a messy bedroom, harsh lighting or no lock on the door can quash the desire for sex. Others find novelty or just an escape from the everyday a turn-on, so booking into a hotel room could provide a temporary libido boost.

Mindfulness
Psychological factors such as anxiety about pain or sexual performance, having a negative body image, or worrying about how long it takes to orgasm, are common sources of low desire in both men and women. An overly long to-do list can also kill the mood. Combat this by focusing on being in the moment, and fully engaging your senses of smell, sight, touch and taste.

Food
From chocolate to oysters, the internet is riddled with suggestions of foods that act as aphrodisiacs. While some of them contain nutrients that could theoretically enhance blood flow to the genitals, or boost someone’s mood or energy levels, the evidence for them boosting desire is weak. Some of these foods may have an acquired a reputation as aphrodisiacs because they were once perceived as exotic or luxurious. This, combined with their reputation as sex enhancers, might help to get some people in the mood – but there is no magic sex pearl in oysters or any other food.

Talking
Poor communication, criticism, lack of trust or unresolved conflict can all take their toll. “Often, when someone is describing a sexual problem, what they’re actually talking about is ‘I don’t feel emotionally connected to my partner’,” says Ammanda Major, a sex and relationship therapist, and head of service quality and clinical practice at Relate. Take time to listen to your partner, including how their day has been, and any worries they may have. Finding ways to express what you like and don’t like is also essential. “The way you want more sex is by enjoying the sex that you are having,” Nagoski says.