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It's Too Darn Hot: How Heat Affects Your Diet

The heat waves streaking across the South and summer heat in other parts of the country as well bring up questions in people's minds about whether they should change their eating habits in such conditions.

Some questions come up a lot in the summer:
- Does our metabolism go up when it's hot?
- Do our calorie needs change?
- Does our appetite go down?

Last week I reviewed some ways to calculate your calorie budget and BMR. So, do our calorie needs change or does our metabolism increase during the hot summer temps? Well, maybe yes, but probably no. Our bodies are well-tuned to keep things at status quo. If anything, our metabolism may go up when we're cold, as our bodies need to work harder to maintain our temperature (by shivering). In the heat, our bodies actually slow down a bit to try to conserve energy so as not to overheat. But none of this really makes any significant change in our BMR or how many calories our body needs.

What is important to note is that in hot weather your body is prone to dehydration and this actually can have an effect on your metabolism. In the course of an average day, sweating, breathing, and waste elimination together leach more than 10 cups of water out of your body - and that's without exercise. If you don't replace what you've lost, you may become dehydrated; your system literally begins to dry out.

Dehydration lowers your body's energy levels, too. Because blood is mostly water, when you're dehydrated the volume of your blood diminishes, lowering amounts of oxygen and nutrients that reach your tissues. Recent studies show there's a trickle-down effect on metabolism: dehydration slows your system to such an extent that you burn fewer calories than you would otherwise during the course of the day. And dehydration can cause other undesirable symptoms, including headache, dizziness, muscle weakness, and a dry, sticky mouth.

Some people say that their appetite decreases when it's hot outside. If that's the case, you should still try to eat small frequent healthy meals throughout the day. Many people find cool gazpacho refreshing in hotter weather. Try my easy recipe for Icy Gazpacho with Fresh Lime.

The takeaway here: When it's hot outside, drink plenty of water, and don't skip your workout!

When it's super hot outside, try not to exercise during the hottest part of the day, especially if you're exercising outdoors. Early morning and evenings are your best bet. To make sure your body doesn't overheat, monitor your heart rate. Some people invest in a simple heart rate monitor. It's also important to don the appropriate workout attire. Don't wear sweats or heavy clothes while working out when it's hot. Sweating more doesn't help you burn more calories; it just may dehydrate you more. And most important, as I mentioned, stay hydrated!

So how will you take advantage of the summer heat and make it work for you?

In these hot months while the show is on vacation we'll still be here each week, offering you tips, guidance, recipes, and more. We'll also be giving away a year-long membership to the Biggest Loser Club every week. This week, watch my Twitter feed @cherylforbergRD for chances to win. I'll ask a question related to this post, which you can answer for a chance to win. And if you don't use Twitter, don't worry: there'll be a different way to win next week.

For more nutrition and cooking tips, visit Cheryl's website FlavorFirst.com, and follow her on Twitter and Facebook.