Saturday, March 12, 2011

Too Little of a Good Thing?

You know how I feel about the overconsumption of carbohydrates. If -- like most people in this country -- you’re overweight after a lifetime of eating a carb-heavy Standard American Diet (S.A.D.), switching to a Paleo approach to nutrition will result in loss of body fat. After all, a person who stops eating grains, sugar and legumes will naturally take in less carbohydrate than before.

But what if you’re already lean? What if you’ve cut your carb intake (by going Paleo or Atkins or Weston A. Price or whatever) and your metabolism’s no longer out of whack? And what if you’re regularly (and intensely) exercising? Are you still supposed to avoid carbs?

The short answer: No.

Here’s the thing: The Paleo diet isn’t intended to be a low-carb diet, and it doesn’t require strict avoidance of carbohydrates. In fact, going super-low-carb may not be optimal for many of us in the CrossFit community.

In the March 2011 issue of The Performance Menu (subscription required), Scott Hagnas of CrossFit Portland points out that an individual’s carbohydrate needs are very different if “you are a firebreathing athlete or are already lean.” Yet many of us continue to restrict our carb intake even after it no longer makes sense to do so. As Hagnas puts it:
One common pattern I often see is the guy or gal eating a low carb, strict Paleo diet at, say, around 50 grams of net carbs per day. This person is training hard, hitting regular metcons, and perhaps doing some intermittent fasting on top of it. While this regimen may feel great at first, after a while this person becomes tired but can’t sleep well. They find they can’t drop some pesky belly fat, often develop a caffeine addiction and are cold all of the time. Finally, they end up with low libido. Yay for healthy living!

Hagnas points out that maintaining a strictly low-carb lifestyle while CrossFitting can cause a host of problems, including:
  • Chronically elevated cortisol / catecholamine levels (and suppressed secretory IgA antibody levels), which will weaken your immune system.
  • Insulin resistance: “Higher free fatty acids during ketosis promote insulin resistance to spare whatever little carbohydrates are available for the central nervous system. Toss in high cortisol from stress due to excessive exercise and quite possibly other lifestyle issues, and you end up with chronically elevated blood sugar -- even in spite of a strict low carb diet.”
  • Lowered testosterone levels (due to excess cortisol production).
  • Disregulation of thyroid hormones: “Conversion of T4 to the active T3 is impaired, with the T4 getting converted instead to the metabolically inactive reverse T3. Body temperature and the metabolic rate drops when this happens, and blood glucose begins to run higher.”
I’ve occasionally stumbled into the mental trap of conflating “carbs” and “grains,” but that’s just me being dumb. The fact that a subset of carbs (grains, sugar, legumes) are associated with the rise of diseases of civilization doesn’t mean that all carbs are evil.

The moral of the story, as Hagnas puts it:
If you are regularly performing metabolic conditioning, even if you limit yourself to 3-5 minutes of very intense activity, then I’d ratchet your carbohydrate intake upward. Consume your carbs not only in the post workout window, but also throughout the day.
Of course, just ‘cause you work out hard need to take in more carbs doesn’t give you license to indiscriminately “carbo-load” by downing a pizza and a stack of pancakes. Stick to veggies for your carb sources: yams, sweet potatoes, beets, chestnuts, etc. Have some protein, too. Just don’t include fat or fruit in your post-workout meal -- fat'll inhibit your body's ability to replenish your muscle glycogen, and the fructose in fruit will prioritize the replenishment of your liver glycogen over your muscle glycogen.

Time to stock up on starchy tubers, y'all.