It’s enough to make your testicles shrink. Global research has shown that men’s mean sperm concentrations have dropped by 51.6% since the 1970s – and this decline is accelerating at an astonishing rate, from 1.16% per year to 2.64% per year since the year 2000 (read our exclusive investigation, “Sperm counts in freefall: is the male infertility crisis an existential threat to humanity?”).

Combined with evidence of decreasing levels of testosterone, the primary male sex hormone in sperm production (“Do you have low testosterone levels?“), a rise in erectile dysfunction among men under 40, and a “spectacular” global surge in testicular cancer, experts are warning that these alarming trends represent “the canary in the coalmine” for men’s reproductive health (read our exclusive investigation, “Are Men Facing A Terminal Decline in Testosterone?”

Nobody knows exactly what is going on. And there are plenty of scientists who say things might not be as bad as they seem. But there is a strong academic consensus that rising male infertility issues are likely to be down to two main causes: the obesity crisis – driven by sedentary lifestyles and poor nutrition – and the hormone-disrupting chemicals found in plastics, food wrapping, cleaning products and pesticides. Male infertility can be caused by various other factors. But given that a wealth of scientific evidence now clearly links infertility with health and environmental issues, simple lifestyle changes can help most men protect their own reproductive powers.

1. Pump up your workout plan

Not all fit men are fertile. And not all unfit men are infertile. But there is irrefutable data which links sedentary modern lifestyles with lower sperm concentrations and testosterone levels.

Men who watch more than 20 hours of TV per week have 44% lower sperm concentrations, while men who do 15 hours of moderate to vigorous exercise per week enjoy 73% higher sperm counts, according to research published in the British Journal of Sports Medicine.

“I think the mantra is that your sperm will tell you how healthy you are,” says Dr Channa Jayasena, a specialist in reproductive endocrinology at Imperial College London. And it’s never too late to dig out your running shoes, bike, tennis racket or gym kit. A study published in the journal Reproduction found that sedentary men who started doing moderate exercise 3-5 times per week had a 14.1% higher sperm concentration and 21.8% more sperm cells after six months of training.

2. Shift your spare tyre

Obese men are three times more likely to have poor semen quality, and a Body Mass Index (BMI) above 25 is associated with a 25% reduction in sperm count.

Studies have found an association between a man’s waist circumference and his ejaculate volume. And obesity is linked to an elevated risk of sexual dysfunction. The message couldn’t be clearer. “There’s an exquisite relationship between body mass index and obesity and male infertility,” says Dr Jayasena. “So that’s kind of what I’d call a no-brainer.”

But if you’ve let yourself go, don’t panic: weight-related declines in fertility appear to be reversible. A Danish study found that obese men who lost weight though an eight-week low-calorie diet saw a huge 41% spike in their sperm count.

3. Move more often

Desk-based jobs are now the norm, but sedentary work is associated with poor semen quality, according to research published in the Human Reproduction journal. “It is a remarkable fact about modern lives that so many people’s jobs have them seated for large numbers of hours,” says Professor Richard Sharpe, of the MRC Centre For Reproductive Health at The University of Edinburgh. “And we know from very well-done studies that that slightly elevates your scrotum temperature, which is bad news for sperm production. Sperm production usually takes place at around 34 degrees, so about 3-3.5 degrees below core body temperature. So keeping your scrotum and your testes cool is important.”

When you are seated, air does not circulate around your scrotum as well to enable cooling. So get up and walk around more often. This is not a miracle cure. But if you’re trying to father a baby, Professor Sharpe such “small lifestyle changes” represent “common sense.”

4. Buy some baggy boxers

Men who wear baggy boxers have a 25% higher sperm concentration than those who wear tight-fitting underwear.

“They do (help) actually, in the short term,” insists Dr Jayasena. “We certainly would advise couples who are finding it difficult to get pregnant to think about these basic things. And just checking that they’re not in spandex, cycling around the park for three hours at a time. That has been shown to heat up the testes and damage sperm.”

Professor Sharpe says wearing looser trousers may be sensible too, given the known links between heat exposure and sperm production. Those skinny jeans may look the part, but they’re not great if you’re trying to get your partner pregnant.

5. Avoid hot baths, hot tubs and laptops

For the same reasons, hot baths and hot tubs may have a negative effect on male fertility. Research has clearly shown that regular heat exposure can affect sperm quality and result in delayed conception.

Dr Jayasena warns against lounging in the bath with candles and music for an hour. Studies have even shown that laptop use increases scrotal temperature and may affect long-term sperm production. So keep your laptop up on your desk.

6. Learn how to relax

Modern life is stressful, but research has shown that stress can impair sperm concentration. One paper, which focused on young men with a median age of 19, found that those with the highest self-reported stress levels had 38% lower sperm concentrations than their chilled-out peers. Music. Yoga. Meditation. Walks. Whatever helps you to nuke stress is likely to aid your reproductive health too.

7. Follow a Mediterranean diet

A Mediterranean diet, which typically contains a high intake of vegetables, fruit and seafood, have a more positive impact on male reproductive health than Western diets full of processed meats, sugary snacks, packaged meals and fatty food, according to a study in the Human Reproduction journal.

To protect your fertility, Professor Sharpe says it is time to “push aside” the unhealthy Western diet. “There’s pretty good evidence that that is associated with, or is the cause of, the obesity crisis, and all the disorders that come along with that – one of which is that there are small negative effects on sperm quality and testosterone levels,” he says.

Remember that the fertility gains from a healthy dietary tweak can be emphatic: research has shown that men who switched to a Mediterranean diet were rewarded with a subsequent rise in sperm concentration and total sperm count after six months.

8. Cut out drugs and alcohol

Bodybuilding and recreational drugs are strongly linked to male infertility. “The big one is anabolic steroids, but also opioids and painkillers and obviously heroin,” says Dr Jayasena. “Smoking is a no-no,” adds Professor Sharpe. A major review of 20 studies found that smoking has negative effects on sperm count, sperm motility and sperm shape.

Alcohol is okay in small amounts, but binge-drinking is bad news. “What I would always say to guys is that there’s very little evidence that things are in themselves catastrophic,” says Allan Pacey, a Professor of Andrology at The University of Sheffield Medical School. “There’s no point in trying to be a monk, because that will just make you unhappy. Don’t binge drink. But a beer with your tea is fine.”

9. Limit chemical exposure

Numerous studies, including a major research paper in Environmental Sciences Europe, have found that environmental chemicals have “a significant impact” on semen quality, leading to decreased sperm concentration and higher levels of infertility. Endocrine-disrupting chemicals (EDCs) appear to undermine a man’s hormonal health and sperm production.

These chemicals, such as phthalates, which make plastics soft and flexible, and bisphenol A (BPA), which is found in hard plastic bottles, are hard to avoid. But there is enough worrying scientific evidence out there to suggest men should take simple precautions. Use glass storage tubs and drinks glasses, instead of plastic ones; limit your use of powerful household cleaners; dodge detergents and soap which are high in fragrances; and avoid plastic food wrapping, packaged food and ready meals.

“Another good consequence of eating a healthy diet, with low amounts of processed food, is that you reduce your exposure to environmental chemicals, because most of those chemicals, particularly the plasticisers, are associated with processed food and high-fat food,” says Professor Sharpe.

10. Trust in the process

Men struggling with infertility should not expect instant results. But if you maintain these lifestyle changes, you can make positive progress. “Remember that to make one sperm takes about 10 weeks, so you’re not talking about: okay, I’ll start eating healthily and tomorrow we can try (for a baby),” says Professor Sharpe.

Professor Pacey agrees that men benefit most from making “sustained” changes over a three-month period: “If you give up smoking on Friday, your sperm isn’t going to improve by Monday. But if you gave up smoking in December, it might be better by March, because the whole sperm production process takes three months.”