Cyclic ketogenic diet
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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 as a way to maximize fat loss while maintaining the ability to perform high-intensity exercise. A ketogenic diet limits the number of grams of carbohydrate the dieter may eat, which may be anywhere between 0 and 50g per day. The remainder of the caloric intake must come primarily from fat sources and protein sources in order to maintain ketosis (the condition in which the body burns fats and uses ketones instead of glucose for fuel).
The Cyclical Ketogenic Diet can be complex, as it requires 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.
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. Some people report feeling 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 and more consistent energy.
Although most people report a waning of cravings while in ketosis, some people may crave carbohydrates during ketosis for psychological reasons. During a hypocaloric ketogenic diet, the carb cravings may combine with hunger pangs, making matters worse. (However, it is noteworthy that most people report having no hunger pangs on a ketogenic diet, due to its higher fat and protein contents, which help to increase a sense of fullness).
A CKD offers a way to combat this. It offers a cyclical "refeed" (sometimes also called a carb-up). During this phase, the diet consists mostly of complex carbohydrates, with limited fat, sucrose and fructose. Since the glycogen stores in the 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 usual dietary intake. While a typical CKD consists of 50g or less of carbohydrate per day, the typical refeed consists of 450-600g of carbohydrate. A weight gain of 1-2 lbs is usually reported during refeeding; this is mainly water and normally lost in 2–4 days.
The goals of a refeed are threefold:
- to refill depleted glycogen stores
- to upregulate hormones and thyroid activity that are suppressed during dieting
- to provide a psychological "break" that makes the rest of the diet easier to bear
The refueled glycogen stores can then be used for higher-intensity training to maintain or increase endurance / muscle mass after the refeed. Normally this sort of training would be relatively impossible on a pure ketogenic diet, as glycogen stores in the body are almost constantly depleted.
The refeed process can lead to gaining fat if more carbs are consumed than needed to replenish glycogen stores. The timing, duration, and macronutrient composition of a refeed are crucial to the overall success of the diet.
According to a published article in the British Journal of Nutriton a test group who consumed less than 40 grams of carbs for two days saw improvements in insulin resistance. Examples of carb cycling could include:
- Low Carb Intake Day 1
- Low Carb Intake Day 3
- Low Carb Intake Day 5
- High Carb Intake Day 2
- Med Carb Intake Day 4
- Med Carb Intake Day 6
- High Carb Intake Day 7
- McDonald, L. (1998). The ketogenic diet. Austin, TX: Body Recomposition.
- Bough K.J., Eagles, D.A., and Kossoff, E. (2007). Diet and epilepsy. New York, NY: Nova Science.
- Harvie, M (2013). "The effect of intermittent energy and carbohydrate restriction v. daily energy restriction on weight loss and metabolic disease risk markers in overweight women". British Journal of Nutrition. 110 (8): 13. doi:10.1017/S0007114513000792. PMID 23591120.