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Venus Williams describes herself as 'a cheagan'. To explain, that's a vegan who cheats occasionally.
But there are only occasional moments of weakness from someone who used to be drawn to steaks on the menu. 'The power of plants' is the slogan for the commercial that Williams appears in for a make of dairy-free milk, and you could give her run to the semi-finals of Wimbledon the same branding.
This is the first time since the 2010 US Open that Williams has ventured this deep into a Grand Slam tournament and, far more significantly, it's her first appearance in a major semi-final since she was diagnosed with Sjogren's Syndrome, an auto-immune disorder, in 2011.
Suffering with fatigue, aching muscles and shortness of breath, and with her saliva and tear ducts under "attack", she converted to veganism, or cheaganism. Put in the simplest of terms, the more fruit and vegetables Williams can eat, the more energy she has, and the further she can go into the draw.
That's why she packs a blender when she travels to tournaments, which she uses to make herself a gingersnap smoothie for breakfast (ginger, strawberries, orange, pineapple, baby kale and almond milk). Lunch could be a bowl of lentils, followed by a salad.
"I always like to have massive amounts of fruit and vegetables - that's when I feel my best," Williams told Shape magazine.
Of course, Williams isn't the only player at his tournament to follow a strict diet. Andy Murray spoke the other day about eating a whole cantaloupe melon for breakfast, and Novak Djokovic's enthusiasm for healthy eating is such that he has written a book about it, as well as recently opening a vegan restaurant in Monte Carlo.
I always like to have massive amounts of fruit and vegetables - that's when I feel my best
But it's no exaggeration to say that Williams wouldn't be on Centre Court on Thursday - where she will play Germany's Angelique Kerber - if it wasn't for her blender and the self-control she shows in restaurants.
Apparently Williams' rare lapses can come when her dinner companion turns around for a moment and leave their plate unprotected - when they turn back to the table, they might find that their food has disappeared.
In a past life, Williams used to love cherry pies. But now she is in a stage of her life that she calls 'Venus AD', or 'Venus after diagnosis', and there can be no more cherry pies: "Sugar is verboten."
On her own website, Williams describes Sjogren's Syndrome as her "greatest opponent" (at first, doctors wondered whether she had adult-onset asthma, and prescribed medicine that brought no "relief"). "Living with the disease has brought about changes in Williams' lifestyle," the website continued. "Like any other opponent, though, Williams has attacked it in her usual aggressive style. She has become an advocate of a vegan and raw food diet, which helps to minimise the inflammation brought on by the condition."
One of the other changes that Williams has made is to her training schedule; she now has one or more rest days a week (though it's plainly not possible to schedule in this breaks during a Grand Slam). Naturally, there are days when she is training or playing and she feels fatigued around 2pm, but she pushes on through.
Even if Williams wasn't suffering from the disease, this would be a remarkable story. At the age of 36, she was the the oldest woman in the draw when the tournament began, and now she is the oldest Grand Slam semi-finalist since Martina Navratilova's run here at the 1994 Championships.
But Williams, one home-blended gingersnap smoothie at a time, is grappling more than Father Time. Her younger sister Serena could end up leaving London with 22 Grand Slam titles - so equalling Steffi Graf's record for the modern era - and the two of them could contest an all-Williams Grand Slam final for the first time since the 2009 Wimbledon.
But the story of how 'Venus AD' played in a semi-final again is arguably the greatest tale of all at these Championships. Why, you might even put it above the five summers when she won this tournament.
