Carbs vs Low-Carb

May 31, 2019

Carbs vs Low-Carb

Consistent Inconsistency

One of the more interesting debates in the low carb community is whether or not to sprinkle carbohydrate-rich “cheat meals” in the diet throughout the month for microbiome support, hormonal balance, antioxidant status, and general wellness. This is part of a larger debate on whether or not carbohydrate fluctuations should follow the seasons. On paper, the argument for the intermittent inclusion of moderately-high carbohydrate days with greater fruit consumption in the summer makes a lot of evolutionary sense. However, nutritional science is anything but sensical.

This is a great article from Chris Masterjohn, offering a small glimpse at the confusion: Sugar is the ultimate antioxidant and insulin will make you younger:

In one recent study, looking at a mere 75-gram dose of carbohydrates (a small rice bowl’s worth) this practice actually looked quite harmful:

See, there’s a side effect to keeping insulin low and fat oxidation high — the ability to rapidly switch off gluconeogenesis in the liver and shuttle away exogenous glucose seems to take a few days to reboot. Paradoxically, just beyond this short timeframe, insulin sensitivity is generally seen as being improved. And during a low-carb diet, glucose and insulin are remarkably steady, mimicking a state of profound insulin sensitivity, where it’s common to maintain very low serum triglycerides and a very low A1C. But in this interim period, high glycemic foods do seem to become higher glycemic foods, and unhealthy junk foods seem to become borderline hazardous foods.

A while back, I wore a continuous glucose monitoring device to get a glimpse of the mechanics that I had read about. This is what a series of blood sugar spikes looks like.

Blood sugar spike on calibrated CGM data

By comparison, this is closer to what we would expect to see from a HFLC sort of diet:

Uncalibrated CGM data with outliers removed

Earn your carbs

This situation can be attenuated to some degree with resistance training to increase the sugar sponge-like GLUT4 receptor activation in muscle tissue, giving credence to the fitness community’s proverb “you have to earn your carbs.”

It isn’t clear to me is whether a well-formulated low carb diet would be worse off without these sugar and starch boluses. If they are in fact beneficial, it’s not clear which frequency would be most beneficial. If we know the rules, we can break them effectively — but what if we can never learn the actual rules to optimize our game?

My takeaway is that a “carb refeed day” should generally be a polyphenol-rich, low-glycemic food day that looks more like a superfood day than a junk food day. This, I feel confident about. Since stress and poor sleep can contribute to reduced glucose uptake, it also makes sense to place a carb refeed day on a calm, well-rested day. I think this will be an interesting space to watch as upcoming research is able to examine these edge cases in better detail.