Dr Byrne's analysis of competitors in the Singapore Army Half-Marathon failed to find any relationship between the amount of water consumed and overall performance in the race.
As a result he claims that drinking too much water during a marathon could be counter-productive.
"I would encourage those people taking part in today's Marathon to be well-hydrated before the race, but not to feel they need to drink water throughout the event," Dr Byrne concluded.
"Listen to your body and drink if you feel thirsty, but drinking several litres of water will not help you run any faster."
The organisers of this year's London Marathon have made available an additional 2,600 bottles of water at each of the 23 water stations scattered around the course in an effort to tackle the expected 23C peak temperatures in London today.
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