Weight loss improves sperm count and concentration in obese men

2023 keynote

Published 09 June 2023

The study for the Human Reproduction keynote lecture opening this year’s annual meeting found that weight loss induced by an eight-week low-calorie diet was associated with improved sperm concentration and count in obese men, which was maintained (in some) after one year’s continued weight control.

Sperm concentration and sperm count were both improved in obese men after an eight-week diet-induced weight loss. This improvement in semen parameters was maintained after a year of continued weight management following randomisation to one of four weight loss strategies. The study, published in 2022, was selected for the Human Reproduction keynote lecture, scheduled as ever to open this year’s Annual Meeting.

This traditional opener is an honorary lecture given by the author of the most downloaded recent original paper from the four ESHRE journals. Altmetrics (lay press reports, tweets, Facebook likes) are also taken into account and this year Dr Romain Barres, fittingly from the University of Copenhagen, was invited to present details of the study.(1)

The trial, performed between 2016 and 2019, included 56 obese men (BMI 32-43 kg/m2, but otherwise healthy) assigned to an initial eight-week low-calorie diet (800 kcal/day) and then randomised to 52 weeks of one of four weight management strategies: placebo and habitual activity, exercise training and placebo, a glucagon-like peptide-1 (GLP-1) analogue with habitual activity, or the GLP-1 analogue in combination with exercise training.

Results showed that the 47 men completing the study lost on average 16.5 kg body weight during the eight-weeks low-calorie diet, which significantly increased sperm concentration (from 78.5 ± 74.9 to 91.7 ± 70.8 million sperm/ml) and sperm count (from 191.2 ± 189.4 to 250.6 ± 319.4 million sperm/ejaculate). These improvements were maintained over 52 weeks in men who maintained their weight loss, but not in men who regained weight. However, semen volume, sperm motility and motile sperm count did not change. At 52 weeks, the combination of the GLP-1 analogue with exercise was more efficient at maintaining weight loss than the two interventions alone, while those in the placebo group not surprisingly regained weight.

Barres took this study as a prelude to a further exploration of diet and exercise in men and the mechanisms by which an increasing prevalence of obesity is passed on by epigenetic factors. A very recent study, for example, showed that diet and obesity independently affect sperm motility, while dietary effects have been observed in a range of morphological, testicular and sperm traits. However, said Barres, the relative influence of protein, fat, carbohydrate and their interactions appear to differ depending on the trait being examined - for instance, unpublished work from the same research programme suggests that a low protein high-carbohydrate paternal diet may induce an anxiety-like phenotype in male offspring, or that a low protein diet appears to remodel the DNA methylation profile of spermatozoa.

The most intriguing aspect of these findings is that paternal sperm DNA methylation has been associated with early signs of autism risk. Thus, while the aetiology of autism disorders may be partly explained by genetic factors, some may also be attributed to environmental factors. One study cited from 2014 found that paternal obesity was associated with a 73% higher risk of having a child diagnosed with autism than with non-obese fathers.

The study report from Human Reproduction was, according to HR editor-in-chief Nils Lambalk, the leading candidate from the list eligible for this award, reflecting the broad interest in factors contributing to sperm parameters and beyond to metabolic health. And as Romain Barres made clear in his lecture the influence of diet and exercise cannot be restricted to sperm and its epigenome, but may extend to a wider range of male reproductive - and even non-reproductive - traits.

1. Andersen E, Juhl CR, Kjøller ET, et al. Sperm count is increased by diet-induced weight loss and maintained by exercise or GLP-1 analogue treatment: a randomized controlled trial. Hum Reprod 2022; 37 :1414–1422.

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