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Men in the healthy weight range have healthier sperm than men who are underweight or overweight, a recent review of research concluded.  

The review looked at data from 60 studies and, taken together, they show that being overweight or obese reduces sperm quality and causes changes in some of the reproductive hormones involved in sperm production. There was also evidence that being underweight affects sperm health with underweight men on average having fewer normal-looking sperm.  

Male problems contribute to many cases of infertility among couples. For about 20 per cent of infertile couples, the problem is with the male, and for about 30 per cent of couples the problem is with both partners. 

Male fertility depends on the quantity and quality of a man's sperm. When a man has his semen analysed, a doctor examines the total number of sperm, sperm concentration, the proportion of normal-looking sperm and the proportion of sperm swimming well to assess quality.  

For men who want to have kids, being in the best possible health before trying for a baby increases the chance of pregnancy and gives the baby the best start in life. This includes striving to be in the healthy weight range to boost sperm quality.  

Losing weight can be hard but men and women are twice as likely to make positive health behaviour changes if their partner does too. So, a joint approach to losing weight and increasing physical activity by partners who want to have a baby will improve their chances of achieving this goal. 

To reach a healthy weight, experts recommend:  

  • Getting support; 

  • Learning about nutrition and healthy eating; 

  • Setting realistic goals and giving yourself enough time to achieve them; and 

  • Exercising regularly.  



Salas-Huetos, A et al. (2020). Male adiposity, sperm parameters and reproductive hormones: An updated systematic review and collaborative meta-analysis. Obesity Reviews,