Researchers looked at 32 studies to understand how weight loss affects men’s ability to have children. They found that when men with obesity made lifestyle changes like eating better and exercising, their sperm quality improved slightly. However, weight loss surgery didn’t show the same benefits, which was surprising. The study suggests that healthy eating and exercise might help men’s fertility more than surgery, but scientists say we need more research to be sure about these findings.

The Quick Take

  • What they studied: Whether losing weight through different methods (diet and exercise, weight loss surgery, or medications) helps men with obesity improve their ability to father children
  • Who participated: 32 different research studies involving men aged 18-50 who were overweight or obese and tried to lose weight
  • Key finding: Men who improved their diet and exercised regularly showed small improvements in sperm quality, particularly in how many sperm moved normally and swam properly. Weight loss surgery didn’t show the same improvements, even though it caused more weight loss
  • What it means for you: If you’re an overweight man wanting to improve your chances of having children, focusing on healthy eating and regular exercise may help more than considering surgery. However, this research is still developing, and you should talk to a doctor about your specific situation

The Research Details

Scientists searched five major medical databases for all studies published through December 2024 that looked at how weight loss affected men’s fertility. They included studies where men were measured before and after trying to lose weight, and where doctors checked their sperm quality or pregnancy success rates. The researchers combined results from similar studies to find overall patterns.

They organized the studies by weight loss method: lifestyle changes (diet and exercise), weight loss surgery, and medications. For studies with enough similar data, they did mathematical analyses to combine the results. For other studies, they reviewed the findings in a narrative way to understand the bigger picture.

The research team was careful to only include studies where men’s reproductive health was actually measured with tests, not just assumed based on weight loss alone.

Understanding which weight loss methods actually help men’s fertility is important because obesity affects many men’s ability to have children, but doctors don’t have clear guidance on the best approach. This research helps separate what actually works from what seems like it should work. By combining many studies together, scientists can see patterns that individual studies might miss.

The certainty of evidence was low overall because most studies were observational (watching what happened) rather than randomized controlled trials (the gold standard where people are randomly assigned to different treatments). Only one study of bariatric surgery was a high-quality randomized trial, and it had a very small number of participants. The studies measured sperm quality as a stand-in for actual fertility, but didn’t always track whether men actually had children. This means the findings suggest potential benefits but aren’t definitive proof

What the Results Show

Lifestyle interventions (healthy eating and exercise) showed the most promise. Men who made these changes had small but measurable improvements in sperm quality: about 0.59% more sperm with normal shape and 10.56% more sperm that swam properly. These improvements were consistent across multiple studies.

Weight loss surgery produced surprising results. Despite causing much more weight loss than lifestyle changes, bariatric surgery didn’t show meaningful improvements in sperm quality or DNA damage. This suggests that rapid weight loss from surgery might not help male fertility the way gradual weight loss from diet and exercise does.

Medications like metformin and liraglutide (used for weight loss and diabetes) had very limited research available. Only five studies examined these drugs, and the evidence wasn’t strong enough to draw clear conclusions about their effects on fertility.

When researchers compared randomized controlled trials directly, they found no significant differences between men who received weight loss treatments and those who didn’t, though the small number of participants made these results hard to interpret with confidence.

The research identified important gaps in our knowledge. Most studies only looked at sperm quality in lab tests rather than tracking whether men actually fathered children. Very few studies examined outcomes from assisted reproduction (like IVF). The newer weight loss medications (GLP-1 agonists like semaglutide) had almost no research examining their effects on male fertility, despite growing use.

This research builds on earlier observations that obesity harms male fertility. The new finding is that the method of weight loss matters. Previous studies suggested that any weight loss would help, but this analysis shows that how you lose the weight appears to be important. The finding that lifestyle changes work better than surgery contradicts some assumptions doctors had made.

The biggest limitation is that most studies were observational rather than randomized controlled trials, which are more reliable. Many studies were small, especially the surgery studies. Most research measured sperm quality as a substitute for actual fertility rather than tracking real pregnancy outcomes. The studies didn’t always measure the same things in the same way, making comparisons difficult. There’s also publication bias—studies showing positive results are more likely to be published than negative ones, which might make the benefits seem larger than they really are

The Bottom Line

Men with obesity who want to improve their fertility should prioritize lifestyle changes: eat a balanced diet and exercise regularly. The evidence suggests this approach may help sperm quality (moderate confidence level). Weight loss surgery should not be chosen specifically for fertility benefits based on current evidence (low confidence level). Medications need more research before recommendations can be made (very low confidence level). All men should consult with their doctor before making major changes, especially if fertility is a concern

This research is most relevant for overweight or obese men aged 18-50 who are trying to have children or planning to in the future. It’s also important for their partners and doctors helping them plan for pregnancy. Men considering weight loss surgery should know that improving fertility isn’t a guaranteed benefit. Men with other health conditions should discuss weight loss methods with their doctor, as the best approach depends on individual health situations

Improvements in sperm quality from lifestyle changes typically take 2-3 months to appear, since sperm take about 74 days to develop. For actual pregnancy to occur, you’d need to allow several months of trying after making changes. Weight loss surgery effects would take longer to assess since recovery takes weeks and sperm changes take months. Don’t expect overnight results—fertility improvements are gradual

Want to Apply This Research?

  • Track weekly exercise minutes (aim for 150 minutes of moderate activity) and daily diet quality using a simple scoring system (1-10 rating of how well you stuck to healthy eating goals). This gives concrete numbers to monitor progress toward the lifestyle changes shown to help
  • Set a specific, achievable goal like ‘walk 30 minutes, 5 days per week’ and ’eat vegetables with dinner every night.’ Use the app to log these daily and celebrate weekly streaks. Connect these habits to your fertility goal by reviewing your progress monthly
  • Track weight loss progress monthly (not daily, as it fluctuates), but focus more on consistency with exercise and healthy eating habits. After 3 months of consistent lifestyle changes, consider discussing fertility testing with a doctor to see if sperm quality has improved. Use the app to identify patterns—which weeks had the best habit adherence and correlate with how you felt

This research summary is for educational purposes only and should not replace professional medical advice. The findings suggest potential benefits of lifestyle changes for male fertility, but individual results vary. Men concerned about fertility should consult with a reproductive endocrinologist or urologist who can evaluate their specific situation, perform appropriate testing, and recommend personalized treatment. Weight loss decisions should be made in consultation with healthcare providers considering overall health, not just fertility. This summary reflects research current as of early 2025 and recommendations may change as new evidence emerges