Readers have asked about a dietary concept that fat-burner enthusiasts refer to as “carb cycling”—occasionally or periodically reintroducing carbs into their diets. Achieving ketosis or leptin sensitivity (two states where the body is burning ketones, a byproduct of burning fat as one’s primary fuel) involves lots of individualization and trial and error. But the idea of planning weekly carb eating “cycles” is—at least from my decades of personal and observational experience— akin to a self-imposed slippery slope that people consistently regret.
Of course, if you never achieve a fat-burning state to begin with, carb-cycling is painless, because you’re not switching the body’s primary fuel, which always involves a degree of discomfort. But, for true insulin- and leptin-optimized fat-burners, fat is their body’s primary fuel. The minute a fat-burner starts eating dozens of carbs (and it takes much fewer carbs than most think to throw you out of a fat-burner state, especially if you’re metabolically challenged), the body will default immediately to the fat-storing, sugar-burning quagmire that many of us worked so hard to escape. That first spike in blood sugar signals the brain that you’re suddenly experiencing starvation as a default mechanism of cutting off sensitivity to the hormone leptin in the hypothalamus.
If you’re doing what I call a “close-but-no-cigar” version of “keto” or low-carb (or Paleo, or “low-glycemic”), you won’t feel the typical discomfort of “carb cycling” because you never really achieved a metabolic and hormonal fat-burning state to begin with. Achieving a true fat-burning state takes a minimum of a few transitional (and at least one uncomfortable) days after just one “carb day” (if you can ever get back to a true fat-burning state at all, which some never do). So, with both unwitting and intentional carb experiences, one would be lucky to experience even a day or two of the miracles of true fat-burning and the physical revelations it brings, including unprecedented mental clarity, restful sleep, soaring energy, and, of course, speedy, struggle-free weight loss. It’s a state I equate with being free of the ball and chain that made a good part of my life purely miserable. A state I’ve lived in gratefully for 27 amazing years.
Candida Resurgence Alert
If your body is in true fat-burner mode and not just merely losing weight or burning fat here and there, then those “carb days” will cause not only major discomfort (brain fog, lethargy, and more), but also the cultivation of dangerous candida and other strains of yeast, as the heartiest members of those strains propagate wildly again with each “carb cycle.” All of the recurrent, candida-related bloating infections will promptly return like clockwork each time.
Only very healthy people with lower-than-average vulnerability to the blood sugar, insulin, and leptin-impacting power of carbs can just flip back and forth from using sugar as their primary fuel. Primitive man easily endured flipping in and out of fat-burning and sugar-burning (famine) modes, but thanks to decades of metabolically morphing dietary assaults, most modern Americans can no longer do this without undue stress, as well as energy and microbiome disruption. If you can cycle between sugar and fat burning without feeling pronounced transitional discomfort, then you’re either extremely healthy (and unlikely to carry any excess weight) or you weren’t in a deep fat-burning state to begin with.
Primitive man easily endured flipping in and out of fat-burning and sugar-burning (famine) modes, but thanks to decades of metabolically morphing dietary assaults, most modern Americans can no longer do this without undue stress, as well as energy and microbiome disruption.
Carbs Signal Starvation
Finally, the idea that carb cycling reminds the body it’s not starving, as some have claimed, counters the fact that fat adaptation requires a metabolic state that neurologically senses “times of plenty.” It’s the carbs that signal the brain to go into starvation-protective, fat-hording, and sugar-burning mode.
For ultra fat-burners—who are not only burning ketones but burning them efficiently enough to achieve full leptin sensitivity—consuming dozens of carbs in just one sitting (as many carb-cycling guidelines suggest) will prompt a “famine” signal to the brain. And thus, the satiety signal is suddenly lost (on the spot, after your first sip or bite of carbs), and that “bottomless hunger” and the resulting weight gain return. Some people compound this problem by fasting, but fasting also prompts the body to go into famine mode. Breakfast, for example, instantly becomes unappealing once the fat-burner mode is interrupted with carbs (see my article about discussing a dark side of fasting, including research and my personal and group observations showing disordered eating as a result, at betternutrition.com). The very point of achieving fat-adaptation or, more ambitiously, leptin sensitivity, is to signal the body that you aren’t starving anymore by turning on leptin’s signaling in the hypothalamus, which is critical to every system in the body.
So in summary, if you’ve found the way to get your metabolism to function as nature intended, willfully interrupting it by carb cycling—especially when periodic unwitting interruptions are bound to ensue anyway—is an incredibly bad idea. Instead, focus on mastering and customizing your individual metabolic thresholds, something that will become a more effortless and joyful dietary pursuit than any before it. Why re-attach the old ball and chain of metabolic dysfunction ever again?