With the heat wave we have been going through, training had been a “challenge” to put it mildly. Like many of you out there, I have been focusing on how to adjust my training paces, and properly hydrate for the heat. The other night after a frustratingly hot swim, I came home hungrier than usual. Normally when I get out of the water, I am not very hungry; even after swims of an hour or more. The other nigh, however, I couldn’t get the cookies and sugary goodness in my face fast enough. This got me thinking: with all the discussion around how to hydrate for heat, can we benefit by changing how we eat in the heat?
So I turned to the good ‘ole interwebs to ask the question: What do I need to eat for heat training?
Before discussing the wisdom of the interwebs, let’s review how our body uses nutrition for fuel. [yes, I’m sure you’ve heard this a thousand times. But hopefully, this will have an interesting ending.]
Under “normal” conditions the we use both fats and carbohydrates for fuel. During training or racing, the body will use a ration of carbohydrates and fats for fuel. Our bodies can hold a finite amount of glycogen. The typical runner’s body holds anywhere from 1,600 – 2,000 calories of glycogen . And fat, well, as we all know that just keeps’ hanging on. The primary fuel source will be determined by your heart rate. As your heart rate increases, you the body relies more on glycogen and less on fat.
When we are exposed to heat, the body’s core temperature begins to rise, and so does the heart rate. For every degree the body temperature rises, the heart rate will increase by 10 bpm .
For example, if your HR at 98.6 °F is 150 bpm, when your core temperature heats up to 99.6 °F, your heart rate increases to 160 bpm at the same exertion level.
So what does this mean? When the hot weather drives up our body temperature, we burn through those precious glycogen stores faster for the same level of exertion. Meaning, if you are training in the heat, you will most likely require more carbohydrates . The exact ratio of increased carbohydrates are unclear, but I for one will be trying to up my glycogen intake on hot days and see if I notice a difference.
Before you head out on your next hot training activity, don’t forget to add a few extra carbs along with your hydration routine. Hopefully this keeps you from reaching for the cookies when you get back home.
 Pete Pftizinger, Eat, Drink and Finish Strong
 Dr. Gorgon Blackburn, Exercise and the Heat
 Rebecca Markway Lee RD LDN, What to Eat When Training in the Heat for Fall Endurance Sports