When you do any kind of exercise, it will change your body composition: that much is inevitable. In the long term, tai chi has an incredibly profound effect on your entire body, from the inside out. Your muscles and tendons become softer -- and, paradoxically, stronger. Your bone density will increase. You'll find your emotions are more balanced, and you'll be able to achieve a stronger mental focus. All of these changes are based on moving your body and focusing your mind in entirely new ways. To make the most of your tai chi, it's important to follow a few key dietary principles.
The diet recommendations I'm making here are based on my experience as a tai chi practitioner who works out six times a week, sometimes for three hours at a time. Your mileage may vary. You probably have different body composition and different energy tendencies than I do, so nothing here is absolute. Traditional Chinese medicine (TCM) practitioners recommend an incredibly wide variety of different foods and cooking styles, depending on your basic disposition and any symptoms you might have. As Victoria Dragon notes in her article on TCM & Diet for Acupuncture.com, one of the beauties of TCM is that it recognizes individuality in everything, including diet.
Needless to say, you shouldn't eat a food to which you are allergic or sensitive. If you think you have a food allergy, go get tested by an allergist.
In TCM, one of the core notions is following what's called a "pure, clear diet." This means natural food. It means whole food. It means that you won't get what you need from a frozen cube of tastelessness that you stick in the microwave each night. My tai chi classmates--the people who I've been training with for years now--have noticed that slowly, their tolerance for any processed foods has dropped way down. If you want to feed your body well, you need to cook.
When you're especially starving after a workout, it's tempting to grab the fastest, easiest source of calories. Back at the club where I first learned tai chi, people routinely ate cheap storebought cookies along with their tea during class breaks. But it's important not to gravitate toward simple sugar. A cookie or piece of cake will only leave you feeling draggy if you eat it after a workout, and over time, sugar stresses your entire energy system and causes spleen qi depletion. Don't deplete your spleen qi!
When I was first practicing, I craved pasta and other carbs after a workout. I would head home after the end of class at 10pm, cook a big pot of noodles, and eat them with some bread. Needless to say this was not the best idea, for my digestion or my energy level.
So what's ideal? As a baseline, you'll want to focus on lean proteins, whole grains, lots and lots of vegetables, and some fruit.
In TCM, eating raw veggies is generally speaking not considered the best idea. Raw veg makes your body work extra hard to digest it. I know there are a lot of raw foodists and general nutritionists out there who think it's a great idea to make your body work harder. If it wants calories, the logic seems to go, it has to slave to get them!
But the TCM approach suggests that the best way to keep your qi levels high is to give your body food that it doesn't have such a hard time with. Lightly steamed veggies are great. In the depths of winter, when it's absolutely freezing out, a hearty, root vegetable-laden stew is terrific for you, and will help you stay warm. When it comes to doing tai chi, which warms you greatly on the inside, a good rule is that warming foods are best.
Whole grains are the foundation of a good diet according to many TCM practitioners. I've been experimenting lately with starting my day with a bowl of porridge of some kind--whether it's brown rice porridge, oatmeal, quinoa, millet, or some other mystery grain, and I've found I have energy to burn and I stay full for hours and hours.
You'll find varying opinions on meat among TCM practitioners, but if you're going to do tai chi intensively, it's best to include some in your diet. I know, I know. A lot of people who are vegetarian are also attracted to activities like tai chi. But as a former vegetarian, I can tell you that it's next door to impossible to do tai chi and stay healthy on a vegetarian diet. Meat protein relaxes and nourishes your muscles and tendons in a way that vegetable protein sources, like beans or tofu, and even eggs and dairy, just can't accomplish. I speak from experience on this: I was vegetarian for 13 years before I started experimenting with adding a little bit of fish or chicken back into my diet, and the difference was incredible.
Generally speaking, you'll find your digestive tract is happier when you drink and eat foods that are room temperature or warmer, especially right after a workout or if you've been spending a lot of time meditating.
Good luck with your tai chi, and happy eating!