Once and Future wrote:
Funnily enough I'd just been thinking McColgan was starting to look unhealthily thin. I follow her on instagram for a number of reasons. She's British, she's pretty fast and she was pretty hot (possibly not a good reason to follow someone but here we are). In the last couple of months she's gone from being thin, to unattractively thin. Whether this has any impact on her health, or whether she even remotely cares if some random nobody finds her attractive or not is another point entirely. She seems to be running alright though.
Your observations are correct, but this is NORMAL behavior for any elite runner, male or female. She is reducing her weight in order to peak for the world championship - as soon as that race is over, she will gain weight again until another main event. You don't need to be at 100% of optimal health all-year-round.
As long as it's just for a short time, she will be perfectly fine. Lagat, Meb, Muir, many great runners get chubby in their off-season, then they get lighter and lighter throughout the training season before hitting a low for their peak race, which is usually Olympics or World championship. Then, in the off-season they naturally gain again.
At the level of these athletes, there aren't really any legal ways to get the improvement that dropping 4 lbs would give them. I agree they are NOT healthy for the period of Olympics/World Championshpi/Tour de France (cycling), but most of the year they are just lean but very healthy. All good.