The ashtanga vinyasa yoga practice being what it is — an experiment in observation — the people who practice it regularly naturally begin to track correlations between their eating habits and their yoga practice. As a result, many people have either adopted or imported their own rather esoteric eating and dietary examples. In some cases, people don't adopt or import eating habits, regimens or philosophies so much as they use the practice to fine-tune their own food-related neuroses and eating disorders.
So we can put anorexia and bulimia on a far, far end of the spectrum — it's rare but I've seen it — other food philosphies and ideas I've encountered and/or tried directly myself include vegetarianism, veganism, macrobiotics, raw foodism, fruitarianism, breatharianism (or, as an old teacher of mine called it, "male anorexia") and uropathy (the drinking of one's own urine).
There are a myriad of variations and minute differences. Some of the more extreme and hilarious include eating more (and more!) ghee, eating more chapatis, eating less chapatis, and the complete removal of certain and specific foodstuffs from one's diet, such as deadly nightshades (i.e. potatoes, eggplants, strychnine), sugar, wheat, mushrooms, or eggs.
A woman once asked Guruji if eating dark chocolate would make her more flexible, and Guruji responded with a vigorous "Yes!" Milk chocolate, with its milk and sugar, seems to be a very sattvic food. Guruji, it should be added, has a legendary sweet tooth. The next several mornings, before class, at 5 a.m., the woman showed up at the shala gates hurriedly gobbing down bits of dark chocolate before heading in to practice.
I don't know if the chocky made her more flexible, but if you can work out a way to have the consumption of chocolate legitimized and endorsed as part of your yoga practice, I say go for it.
Unfortunately, at this point I can't say with any certainty that eating certain kinds of food affects in any way my experience on the yoga mat. But I'll head out on a limb here to list the few food and diet generalizations I can make.
1. The daily consumption of generous amounts of water. I don't exactly measure it out, but I'm getting at least 64 ounces a day. The tapas of the daily exertions of the practice refined my discrimination to the point where I realized I was often eating when I was thirsty, misinterpreting my body's signals, and therefore walking around perpetually dehydrated. A can of Mountain Dew and two cups of coffee a day isn't enough liquid.
2. A daily practice. It's obvious (as is most dietary advice, right?), but I'll state it anyway: consistent practice is the mother of skill.
It also forced me to take a long view of things, because once you start practicing every day, the body's more minute and heretofore unnoticed tics and nuances suddenly become readily apparent, and this, in turn, is when the practice becomes a true practice; that is, when you've abandoned accomplishment in order to get through it. A bad physical day — a day of physical discomfort and unease — will quickly wipe out the novelty factor of yoga. The novelty factor: "Look Ma, I'm a yogini! I'm wearing my yoga capri pants, I have my yoga mat bag, and I have my mat! Wow, I just put my leg behind my head!" Injuries also have the same effect, but that's a whole different post.
3. Caloric restriction, especially at night. I'm not going to make any generalizations about what sorts of diets ashtangis should be adhering to, although Pattabhi Jois will highly recommend a vegetarian diet, which is also what I personally believe in and practice, but for those Inuits and Tibetans out there — that is, those of us genetically predisposed and raised to consume either whale blubber and baby seal, or yak meat and radishes — an all-veg diet may not be ideal, and in fact may rot out your teeth, destroy your immune system, and make you crabby and irritable.
But I have noticed a consistent sense of clarity and lightness, as opposed to sluggishness and density, when I began to reduce the amount of calories I consumed in the evening. Many ashtangis adopt this habit while in Mysore, where we get up so early to practice that a heavy Indian dinner, eaten late at night, feels like a real gut-bomb. Over the years I've shifted towards eating big lunches and smaller dinners. The idea being, though, that even during lunch, my portion sizes are reduced.
The ashtanga practice, more than any other system, has built-in failsafes to ensure you're not over-eating or under-eating. If you stay out late with the work crew for an extended happy hour re-mix, horking down margaritas, baskets of free garlic bread, and a dinner of spinach and garlic raviolis, odds are you'll feel a bit sluggish the next morning.
If you under-eat, you feel bendy and light for a day or so, but this degenerates into a physical weakness, as the ashtanga vinyasa practice requires equal amounts of strength and flexibility.
This is why, incidentally, I'd be interested to know how those anorexic and bulimics out there manage to pull it off, although I'm guessing the physiological checks they're writing on their bodies will get cashed that much sooner due to the demands of the ashtanga practice.
We could also speculate about the efficacy of eating less towards evening, too, by taking into account Sharath's practice schedule. Tim mentioned that when he lived with the Jois', they would eat two big meals a day: at 3 and 9 p.m. He would finish those heroic practices the Old Guys used to do (three, four hours alone in the room with Guruji) and then, after waking up from resting pose/black-out, rove the streets of Lakshmipuram like a ravenous bear, looking for something to eat.
So if Sharath is eating a typical south Indian dinner at 9, and then practicing at 2 or 3 a.m., that pretty much blows my observation out of the water, but what the hell.
4. Finally, the other factor that affects my practice with any consistent regularity is the amount and quality of sleep. The less sleep, the more flexible and strong I feel. This, too, is a slippery slope, because while I've had brilliant practice after two hours of sleep, it's simply not sustainable on a day-to-day basis.
Nina and Olaf have a great questions-and-answer page on their site, nilaf.com, where they answer some of the most common questions they're asked. Although they're asked about diet separately, their answer to the question, "Can I do other sports and practice yoga?" really applies here, as they answer that yoga is supposed to bring awareness to the other aspects of our life. Eating is no exception. The idea being, whatever it is you're eating, eat with consciousness.