Eating a high-fat ‘fast food’ meal can reduce testosterone levels by 25% within an hour of ingestion in overweight and obese men, Australian research shows.

And the effect can last for up to four hours, say the South Australian study authors in a recent issue of Andrologia.

The new finding goes some way to explain, at least in part, the well-known link between male obesity and androgen deficiency and impaired fertility. If an obese man regularly consumes high fat meals and snacks throughout the day he will be constantly reducing his testosterone level to 75% of normal, and given that he is likely to be low in testosterone already (given his obesity) he can ill afford this further reduction if he wants to father a child.