Dear Mark: Signs You Should Eat More Carbs

CarbsFor today’s edition of Dear Mark, I’ll be addressing a single article from a highly-lauded intellectual institution: the Huffington Post. I’m kidding of course. The HuffPo has some great stuff, but they’ve also got to pay the bills and fluffy articles inevitably slip through the cracks. This article is one of the latter, claiming to give five definitive signs that you – the personal “you” – absolutely need to be eating more carbohydrates. How does it stack up?

Let’s find out:

While I know you have answered all of these statements in one way or another in various posts I would love to see a response to this article about why we should eat more carbs. While I know it isn’t true, many people see these links on Facebook and other media and believe every word. Reassuringly, there were actually many comments arguing with the article which was great, I just thought it would be interesting to see your response.

Thank you!!!


Excellent question. It’s good to have this stuff together in a single post as a reference, because these are common arguments. Let’s take each one apart separately:

“You have bad breath.”

This is ketone breath, caused by the expelling of ketone bodies through respiration. It’s normal if you’re in ketosis, and it’s actually a good indicator of that particular metabolic state.

So, is bad/ketone breath a sign that you should eat more carbs? That depends. If you’re trying to avoid ketosis, bad/ketone breath means you should eat more carbs. If you’re trying to stay in ketosis, or at least dally there for a bit, bad/ketone breath means you should not eat more carbs. It means you’re doing it right. So I guess it’s true in a sense for certain people in certain situations with certain goals, but it’s not a proclamation of absolute truth for everyone.

“Your workouts are slipping.”

The article bases this claim on the supposition that without carbs, you can’t build muscle – that instead of being used toward muscle protein synthesis, the protein eaten by a low-carber is broken down into glucose. Sounds somewhat reasonable. However, a recent review of the evidence concludes that while it’s a popular claim, there is no evidence that the addition of carbohydrates to a protein supplement will increase, acutely, muscle protein synthesis and, chronically, lean body mass to a greater extent than protein alone. All you need is protein for hypertrophy, according to the evidence.

What about the claim that we need tons of insulin to boost muscle growth? Well, we need some insulin, but we don’t need carbohydrates for that. Good ol’ leucine, an amino acid found abundantly in meat and milk, provokes enough insulin secretion to handle muscle protein synthesis when systemic insulin levels are already low. Anyone eating Primal will get plenty of leucine, and almost anyone eating lower-carb will have fairly low baseline insulin levels.

I’ve always said that eating some carbohydrate after a high-intensity, glycogen-depleting workout is the best time to eat it. You’re more likely to fill glycogen reserves that way and your muscles are insulin sensitive and thus require less to do the job. Exercise even up-regulates something called non-insulin dependent glucose uptake, a glycogen-repletion pathway that allows carbohydrate utilization without any insulin at all.

In my upcoming book, Primal Endurance, I’ll be exploring low-carb, high-fat, and ketogenic endurance training. It’s largely unexplored territory, and since the entire fitness industry revolves around the carb paradigm, I think this book will really turn some heads and open some minds.

“You feel a little fuzzy.”

Going low-carb impairs cognitive functioning, in other words. They cite a press release about a study in which women were either placed on a low-carb or low-cal (but normal carb) diet. After a week of eating their respective diets, the women took memory tests. The low-carb women performed more poorly than the low-cal dieters, and once they resumed eating carbs, their results improved. Here’s the actual study (and here’s the full PDF).

It turns out that they were testing the Atkins diet. The first week was Atkins induction, which basically eliminates carbs except for a few grams plus fiber. The second and third weeks introduced small amounts of carbs back in. According to the Atkins website, this phase of the diet involves eating 12-15 net carbs (carb grams minus fiber grams) and increasing the amount you eat by weekly 5-10 gram increments. So they didn’t go back to bagels for breakfast and sandwiches for lunch; they did not resume eating the same amount of carbs they were before the diet. They simply introduced a few more carbs after eating almost zero and this was enough to restore their mental faculties. They were still low-carb, or even very low-carb and they were almost certainly in ketosis. This sounds an awful lot like the Primal Blueprint Carb Curve, which supports up to 150 grams of carbs per day for maintenance or gradual fat loss.

The difference is that they’d had a week or two to become fat-adapted and get over the low-carb flu. They had begun compensating for the “missing” glucose by incorporating ketone bodies into brain metabolism. Being low-carb is a very different beast than going low-carb. It gets better.

“You’re cranky.”

While serotonin, the “feel-good” neurotransmitter, has difficulty crossing the blood brain barrier, its precursor, tryptophan, can slip past the barrier with the help of insulin and be converted into serotonin. Since carbs famously spike insulin, the article claims that carbs are required for serotonin synthesis and mood maintenance. Is it true?

Kinda. According to some studies, pure carb infusions – think marshmallows, rice cakes, plain toast – do increase serotonin levels and boost mood in certain populations, like people engaged in cognitively demanding tasks. Or high-intensity athletes who are burning up lots of glucose, like dancers (many of whom are elite athletes). They do see mood benefits with moderate carb intakes, but that’s not a matter of carbs so much as it’s a matter of avoiding hypoglycemia. One study cited in the article found that women on a low-carb diet reported a worsening of their mood over the course of a year, although the low-carb arm of the study had twice as many participants already taking anti-depressants, meaning they were kind of in a funk to begin with. That may be why depressed people often have carb cravings, as an unwittingly desperate attempt to synthesize the serotonin they so desperately miss. The problem is it’s not a sustainable or healthy path away from depression (what, are you just going to live on potato chips?) and often (and unsurprisingly) leads to weight gain.

There are better ways, I think. Carbs may boost your mood for a bit, but what happens after? We all have those coworkers who must constantly snack lest they fall asleep at their desks or snap at their cubicle mate. Heck, you probably once were one of those grouchy, snacking coworkers. Meanwhile, your protein and fat-rich breakfast may not get you cracked out and hyper, but it doesn’t leave you yawning when 11 AM rolls around. You’re not cranky if you’re asleep, though, so I guess they win on a technicality.

Exercise also increases the brain’s uptake of tryptophan. In fact, increased brain tryptophan uptake and serotonin synthesis may explain the astoundingly effective antidepressant effects of exercise.

Carbs can certainly help tryptophan uptake, and I’d argue that sane levels of carbs (see the Carb Curve again) are perfectly adequate in this regard, but you can’t get by on carbs alone. The best sources of tryptophan are animal products which the manufacturer tends to package with animal fat, so you can’t really escape the necessity of eating fat and protein for mood. All in all, I’d say most people who’ve gone Primal report improved mood, steadier energy, and a better overall outlook on life. I certainly have. And we don’t need to keep a plastic baggie of crushed up rice cakes on hand to maintain these benefits.

“You’re irregular.”

Constipation, diarrhea, or both are among the most common gut ailments across the Western world – and the vast majority of the afflicted are eating standard industrial diets, not low-carb Primal ones. This is not a problem unique to low-carbers. I’ve always supported the intake of prebiotic fibers to help normalize gut health and digestion. Everyone should probably be eating more fermentable fibers from fruits and vegetables. This is where something like resistant starch comes in.

Remember, low-carb is not zero-carb or zero-plant matter. In my experience, Primal people eat way more vegetation and get way more non-grain fiber than most vegetarians. But if this is a blind spot for you and you are having trouble in the bathroom, then I suppose your gut flora need to be eating more carbs. It doesn’t mean you, the host of the flora, necessarily need to eat more carbs.

Bottom line: this article makes some technically true statements, but misappropriates them in a sneaky, misleading, underhanded way. These “laws” don’t apply to everyone.

Thanks for reading, everyone!


About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending more than three decades educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates flavorful and delicious kitchen staples crafted with premium ingredients like avocado oil. With over 70 condiments, sauces, oils, and dressings in their lineup, Primal Kitchen makes it easy to prep mouthwatering meals that fit into your lifestyle.

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