Lowering the BMI can improve older men's fertility
Reproductive Health Male fertility BMI

Lowering the BMI can improve older men's fertility

Dr. Mónica Faut
Dr. Mónica Faut

In 10 seconds? It’s worthwhile to stay lean into older age if you are a male who wants kids – researchers found that losing extra pounds improves sperm quality.

What’s the story? Evidence of a global decline in human sperm quality over recent decades has been accumulating. Environmental, occupational, and lifestyle factors contribute to this phenomenon. In this context, BMI emerged as a critical factor among older men, with molecular mechanisms underlying the complex testicular changes associated with the exacerbation by concurrent chronic conditions such as obesity. But a recent study says – pardon the pun - “old dogs can still do some tricks”. To be less cryptic: after two weeks of shedding around 36lbs, men’s sperm counts increased by 40 per cent (with sperm count being a key factor in fertility).

Wait, can you explain BMI first? Sure! The Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. Being overweight and obese are associated with excessive fat accumulation. Both conditions can be evaluated using BMI. An overweight person is someone who has a BMI between 25–30 kg/m2 and an obese one is someone whose BMI is higher than 30 kg/m2.

Thank you… so, is there a relationship between obesity and infertility? Yes! Lifestyle factors are associated with infertility, and in men, this association is shown to decrease sperm quality. Some reports show that paternal obesity harms reproductive potential, and this effect is hidden at the molecular and genomic levels. In addition, a meta-analysis involving 13,077 men reported that obese men were more likely to be oligozoospermic (have a low sperm count) or azoospermic (lack sperm in their ejaculate) compared to men within a normal weight range.

Substantial maintenance of weight loss after 52 weeks is associated with improved sperm concentration and sperm count. Source: Andersen, Juhl, Kjøller et al 2022.
Substantial maintenance of weight loss after 52 weeks is associated with improved sperm concentration and sperm count. Poor maintainers (red) had a weight loss of less than 11.7 kg after 52 weeks. Good maintainers (blue) had a weight loss of more than 11.7 kg after 52 weeks. Source: Andersen, Juhl, Kjøller et al 2022.

You mention “older men” in the title, is paternal age an issue? Well, believe it or not, paternal age is also linked to infertility risk. In women, 35 years is a marker of the beginning of increased risks of adverse reproductive outcomes. In men “advanced paternal age” is marked by the decline of semen quality and integrity. However, this advanced paternal age has not been well-defined yet – but researchers and physicians agree that it could start after 34 years of age.

So, it is all related? Apparently, yes! A recent report shows that aging makes the testis more sensitive to other lifestyle factors. According to the authors, BMI emerged as the most critical factor among older men. Although it is poorly understood, it seems that the cells that will become sperm (i.e. spermatogonial stem cells) suffer modest negative changes in healthy older men but this dysregulation turns into something more severe when BMI goes up.

Ok! Could you explain why this report is important? Of course! In a few words: it reveals potential biomarkers for the diagnosis of testis aging and directions for the potential treatment of aging-related subfertility. For this study, the authors studied more than 44,000 different cells! They could establish the relationship between age and BMI at the molecular level with a large sample, and obtain convincing results.

And finally, what else should we know? Although this strategy opens a new way for future research of testicular cells and has the potential to reveal other associations, larger patient cohorts are needed to fully validate most of the results. This kind of strategy could help to establish whether diet, exercise, diabetes, or altered hormone production plays a role in testis aging. For example, an exhaustive systematic review of observational studies concluded that a healthy, balanced diet could improve semen quality and fecundity rates among men. This gives us an extra tool to determine at what age the dysregulation of supporting testis cells emerges, and whether and how it may be reversible.

So, what to eat to boost sperm count?

It is not just about eating! Experts recommend a regular exercise regime (it ramps up testosterone levels and semen quality) but without overdoing it.

It is also important to reduce stress because… it also impacts testosterone levels. I.e. the more stressed you are, the lower the levels of the male hormone go.

In terms of diet, specialists advise taking vitamin C, D, and zinc supplements and eating folate-rich leafy greens for better sperm. Red meat can be a fertility friend if it is lean, providing zinc via food. You should also include food that provides omega-3, like salmon, sardines, and mackerel. (Because the fatty acids contained in them also enhance sperm quality and blood flow). And research suggests eating walnuts because they are rich in antioxidants.

At the same time, the recommendation is to cut down on processed food, alcohol, and coffee as too much of the stuff can damage your sperm.

Dr. Monica Faut has distilled 8 research papers, saving you 27 hours of reading time

The Science Integrity Check of this 3-min Science Digest was performed by Dr. Ralph Papas

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