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The Perfect Day: Tapping Into The Circadian Rhythm

  • By Matt Fitzgerald
  • Published November 8, 2012


What To Eat When
The body has different metabolic priorities at different times of the day. The main priority in the morning and mid-afternoon is energy provision because this is the most active part of the day. The main priority of the evening and night time is regeneration. These priorities are exaggerated for triathletes, who typically train after waking up and before mid-afternoon, and who need to recover from training in the evening and during the night.

Portman advises athletes to prioritise different nutrients in these two separate functional parts of the day. Specifically, carbohydrate, the great energy provider, should be prioritised between wake-up and mid-afternoon. Protein, the body’s main tool for regeneration, should be prioritised between mid-afternoon and bedtime.

At no time are carbs more important than first thing in the morning, especially for athletes who train then.

“When you get up in the morning, you are coming off the longest interval without eating in the entire 24-hour cycle,” Portman says. “Your liver glycogen stores are low at that time. You need to bring those up by eating carbohydrates before you start exercising, or you won’t perform as well.”

In addition, cortisol levels are high in the morning, and exercise brings them even higher. Cortisol is a “catabolic” hormone that breaks down fats, carbs and protein for energy. Without cortisol you couldn’t swim, bike or run very fast. But when cortisol levels get too high, a lot of muscle protein is broken down, compromising recovery. Consuming carbs before and during morning workouts lowers cortisol levels and helps recovery.

When your last workout of the day is behind you, your diet needs to change. While your breakfast and lunch should be packed with carbs (think old-fashioned oatmeal with fruit, and brown rice with stir-fried veggies), your dinner should be high in protein (for example, broiled fish with cooked, spiced lentils and amaranth).

Don’t stop there, though. “Prior to going to bed, take a protein drink,” Portman advises. “It will prevent large increases in cortisol during the night and it will drive some protein synthesis while you’re sleeping.”

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