A cyclic ketogenic diet (or carb-cycling) is a low-carbohydrate diet with intermittent periods of high or moderate carbohydrate consumption. This is a form of the general Ketogenic diet that is used by bodybuilders as a way to maximize fat loss while also building body muscle. A ketogenic diet limits both the number of carbohydrate and protein grams that a person may eat. The remainder of the caloric intake must come from fat sources in order to maintain ketosis. Ketosis is the condition in which the body burns fat (ketones) instead of glucose for fuel. The Cyclical Ketogenic Diet can be complex, as it requires the dieters to closely watch the number of carbohydrate grams they eat during the intermittent period that they are not maintaining a strictly low carb/moderate protein diet. [1]
When following a low carbohydrate diet, for the first few days, there is an adaptation period during which most people report feeling run-down or tired. The slightest exertion causes muscles to burn. People feel irritable, out of sorts, and unable to make decisions. For most people these feelings disappear after the adaptation period, however, and are replaced with feelings of calm and balance, consistent energy.[1]
Not everyone is dedicated enough to wait long enough for the body to adjust, so the potential for burnout on a non-cyclic ketogenic diet (like Atkins) can be high. People crave carbohydrates during ketosis, for physiological reasons. During a hypocaloric ketogenic diet, this temptation becomes even stronger, as the carb cravings are combined with the usual hunger pangs that accompany reduced calories.[2]
A CKD offers a way to combat this. It offers a cyclical "refeed" (sometimes also called a carb-up). What happens during a refeed is that the dieters will change their diet to comprise mostly complex carbohydrates, limiting dietary fats as well as sucrose and fructose. Since the glycogen stores in their liver and muscles are depleted, these carbohydrates go straight to refilling them, instead of being added to the body's fat stores. For this reason, the amount of calories consumed during a refeed can be far above an individual's maintenance intake.
The goals of a refeed are threefold:
a) to refill depleted glycogen stores
b) to upregulate hormones and thyroid activity that is depressed during dieting
c) to provide a psychological "break" that makes the rest of the diet easier to bear
A refeed is risky, as careless individuals can end up gaining fat, instead of losing it, if they eat more carbs than is needed to refill their glycogen stores. The timing, duration and macronutrient composition of a refeed are crucial to the overall success of the diet.[1]