Eating Before, During, and After Training
Just as training regimens are different for the three sports of the triathlon, your nutritional needs are different before, during, and after each discipline. The first thing to know is that you should eat something, especially if your activity is taking place in the morning. When you arise after a night's sleep, your blood sugar is low. If you engage in vigorous exercise on an empty stomach, you will suffer. You will feel weak, possibly dizzy, perhaps sick to your stomach. Certainly your workout will be a poor one and most likely will have to be cut short.
In all three sports, postworkout nutrition should take place within about thirty minutes of stopping. It is during that period that your body is most receptive to the replacement of the glycogen you lost during the workout. Ingest carbohydrates for glycogen replacement and protein for your muscles.
Of the three sports, the least demanding in terms of preactivity nutrition is the swim workout. You can get by on a piece of toast or fruit — just something to elevate your blood sugar level a bit. A sports drink would also work for that purpose. Of course, the more time you have before your workout, the more you can eat without feeling bogged down.
After your swim workout, you should have a good meal that includes protein. Consider oatmeal, for carbohydrates to replenish glycogen stores, and eggs or a smoothie to supply protein for muscle recovery. Do not get your protein from something like sausage and biscuits. Don't ingest greasy food after your swim. Keep it healthy.
Swims rarely last longer than forty-five minutes, so it is highly unlikely you will run out of energy from lack of fuel in your body. Heat won't be an issue because of your surroundings, so hydration won't be much of a problem.
In fact, even if you awake pretty hungry, don't get into the pool with a big meal on your stomach. You will feel sluggish, and cramps are an issue when you combine a full stomach and swimming.
Don't plan on eating during the swim, but you might take a few sips of water or a sports drink. Keep the bottle at hand near one end of the pool so you don't have to get in and out.
Of the three sports, cycling requires the highest caloric intake because most rides are longer than swims or run. It is recommended that you take in 400 to 500 calories in carborhydrates, protein, and fat before any ride lasting an hour or longer. You burn a lot of calories on your bicycle, so you need a good store of fuel to start out.
Also, although eating that many calories may make you feel a bit full, you will manage that fullness much better on the bike than you would out running on the road or the trails.
Foods to consider as a preride meal include oatmeal or cold cereal, fruit, and eggs (but not fried or otherwise greasy). Don't eat a lot of fat, but take in enough calories to see you through the workout.
Be sure you take some additional fluid and fuel (a gel, energy bar, banana, or some fig cookies) along on your ride. You expend a lot of energy on the bicycle, and you don't want to hit the wall half way through your ride, 10 miles from your car. That is a miserable experience you don't need.
You can conveniently carry a gel pack with you on your bike by taping it to one of the bars. If you carry gel, make sure you have water to take with it. If you wash an energy gel down with a sports drink, both will sit on your stomach too long to do you any good.
Run for It
Nutritional preparation for your run is similar to what you need for the bike workout, but it is best to eat less than you would for your ride. A full feeling will hamper you more when you're on foot than when you're riding.
A small bowl of oatmeal would work, but you could probably get by with just one energy gel or half of an energy bar followed by water to aid digestion. Save your sports drinks for when you're actually running, or at least water it down if you're going to drink it before you start.
Most of the training runs for your first triathlon will be of relatively short duration, so you will not be in danger of running out of energy, but it can't hurt to take a gel with you (or the other half of that energy bar) just in case. Bonking is no fun no matter where it occurs.
If you carry a bottle for fluid replacement, a sports drink will serve you better than plain water, especially if it's hot. Pick a drink with a high content of electrolytes, which are essential to prevent cramping and other problems associated with intense activity in the heat.
It will serve you well to purchase a waist pack with a holder for a water bottle. Even on relatively short runs, if the temperature is elevated and it's humid, you will need to replace fluids as you go.