When food's not on the brain, what are we thinking about? Well, if we're anything like the hungry mice studied by neuroscientists at the University Clinic Cologne in Germany, it's about that other (sometimes) forbidden fruit, sex.

Researchers found that when their tiny, pink-footed subjects hadn't been fed in hours, they would choose food over "socializing" with members of the opposite sex. But when the researchers stimulated neurons with leptin receptors (leptin is an appetite-suppressing hormone), the mice ignored their hunger and chose mating instead.

"Activating leptin receptor neurons causes mice to give priority to the social interaction, despite hunger or thirst," noted the study's first author, Anne Petzold. Although the research is preliminary, the study's authors said it could hold clues into better practices to prevent overeating or rebound eating after calorie-restricted dieting.

How can leptin influence your libido?

The University of Cologne neuroscientists studied one of the brain's "feeding centers," the lateral hypothalamus, with a specific focus on the neurons with receptors for leptin and those that produce neurotensin, hormones involved in hunger and thirst. As it turns out, both types of neurons are involved not only in feeding behaviors—but also in sexual behavior.

Researchers tested mice in three states: well-fed, hungry after fasting overnight, and chronically hungry (after spending five days on a restricted diet). They used light to activate the neurons with leptin receptors to see how it changed the mice's behavior.

In the mice who had plenty to eat and drink, as well as the mice who were chronically hungry, activating the leptin neuron did nothing. The well-fed mice prioritized finding sexual partners, as usual, and the very hungry mice said no to sex and went for the food.

But in the moderately hungry mice, activating the leptin neuron shifted their priorities from eating and drinking to sexual desire. They were able to ignore minor hunger or thirst in order to find a sexual partner and have sex.

Does hunger increase sexual desire?

Yes and no. There appears to be a complex interplay between hunger, appetite, socialization and sex drive. But as for whether hunger or appetite suppression causes a higher libido—well, it's a bit more complicated than that. The findings of this study suggest two things:

1. Being very hungry curbs libido.
2. The stimulation of appetite-suppressing leptin neurons makes minor hunger easier to ignore when sex is an option. It is important to note, though, that leptin does not "activate" your libido.

On the other hand, ghrelin, the hormone responsible for telling you you're hungry, also increased libido in mice. So it's not a simple calculation of "appetite suppression = increased sex drive" or that "enhanced appetite = decreased sex drive."

As for how this applies to humans, these findings are consistent with previous research. We know calorie restriction can improve sex drive sometimes, but extreme calorie restriction and hunger can negatively impact sex drive. This study and previous ones demonstrate that delicate balance.

The mouse study has ramifications beyond libido, though. "We have this system which can only regulate moderate hunger, but not strong hunger," a researcher on the study said. "This circuit might contribute to why diets don't work: It's not a problem to reduce your food intake for a short time, but it doesn't work if you try to do it for longer." Such findings may help future research develop new therapies for weight loss.

Is obesity linked to low sex drive?

Obesity has been linked to low libido and sexual desire. Studies have associated body mass index (BMI) with physical limits on sexual activity and lower sexual life score, as well as sexual desire, frequency of sexual activity and satisfaction with sex.

Weight also appears to play a role in sexual dysfunction, and weight loss through medication or surgery may help restore sexual function, but more research is needed. In addition, studies show excessive leptin production—which happens in response to overeating and in states of leptin resistance—may be involved in decreased reproductive function in obese men.

Losing Weight—and Gaining Sex Drive

Because studies link obesity and low sex drive, the best nutrition addresses both issues. The following nutrients may help spice up your sex life while delivering weight control and other health benefits.

• Pomegranate.

  Concerned about testosterone levels? Pomegranate can help boost testosterone and blood flow, which not only helps your sex life, but also promotes longevity.

• Vitamin D.

  You already know vitamin D strengthens immunity and supports strong bones, but research suggests it also supports testosterone levels and plays an important role in male sexual function. An analysis found that 35% of men with sexual performance concerns also had a vitamin D deficiency.

• Avocado.

  Avocados are packed with nutrients that support heart health and eye health, and a 12-week study showed avocados may also help reduce belly fat.

• Lemon verbena.

  This plant is rich in polyphenols that can help promote weight loss without the unwanted side effects of medication.

• Whole grain rye.

  A Swedish study found that dieters who consumed whole-grain rye lost more weight than those who went for refined wheat. Rye bread is also packed with magnesium, which helps support healthy blood pressure—and healthy blood flow during sex—as well as overall heart health.

• Probiotics.

  The type of bacteria you have in your gut may support weight loss, so keeping your gut microbiome healthy is important. Remember, sugar can wreak havoc on your gut, so keep added sugars to a minimum.

How to improve your libido

Wouldn't it be great if turning on (or off) your libido or sexual feelings was like flipping a switch? While some sexual health medications and over-the-counter remedies promise to do just that, sex and sexual arousal is rarely that easy. Body image and self-esteem play a large role in libido. Low sex drive can also be caused by certain medical conditions, such as erectile dysfunction, low testosterone or hypoactive sexual desire disorder.

Many other factors can decrease one's desire for sex and intimacy:

• Medications such as antidepressants and even birth control may decrease sex drive.
• Fluctuating hormones and post-menopausal vaginal dryness can decrease sexual satisfaction and arousal.
• Relationship problems may contribute to low libido.

Thankfully there are plenty of ways to improve libido and reclaim your sexual health. Your sex life may benefit from the following habits:

• Eat healthy and get regular exercise.

  Daily movement and fitness can boost your metabolism and contribute to a higher rate of sexual fulfillment. A healthy diet and regular exercise also help with healthy weight management and self-esteem.

• Decrease stress.

  Arousal is less likely when you are anxious. Learning to relax with your partner can encourage romance and sexual desire.

• Improve communication with your partner.

  Cycles of high libido and low libido are normal in a long-term relationship. Talking about sexual behavior and desires may improve your sex life and satisfaction.

• Talk to a healthcare provider.

  They may be able to identify medication side effects that may be causing low libido or medication interactions that should be avoided. They might also recommend hormone therapy if low testosterone or other hormone levels are an issue.

• Quit smoking.

  Smoking can dampen your sex drive, as can excessive alcohol. Ditch those bad habits for better sexual satisfaction.

References

• Bates J, et al. "Effect of Body Weight on Sexual Function in Men and Women." Curr Sex Health Rep. March 2019. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6771291/     
• Egecioglu, E, et al. "The role of ghrelin signalling for sexual behaviour in male mice." Addiction Biology. December 2014. https://onlinelibrary.wiley.com/doi/10.1111/adb.12202
• Khodamoradi K, et al. "The role of leptin and obesity on male infertility." Curr Opin Urol. May 2020. https://pubmed.ncbi.nlm.nih.gov/32205811/
• Martin, C, et al. "Effect of Calorie Restriction on Mood, Quality of Life, Sleep, and Sexual Function in Healthy Nonobese Adults." JAMA Intern Med. June 2016. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2517920
• Petzold, A, et al. "Complementary lateral hypothalamic populations resist hunger pressure to balance nutritional and social needs." Cell Metabolism. February 2023. https://www.cell.com/cell-metabolism/fulltext/S1550-4131(23)00044-X
• "Leptin helps hungry mice choose sex over food." Cell Press. February 2023. https://www.sciencedaily.com/releases/2023/02/230223132230.htm
• "Low sex drive in women." Mayo Clinic. February 2022. https://www.mayoclinic.org/diseases-conditions/low-sex-drive-in-women/diagnosis-treatment/drc-20374561

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