Cyclical keto: keto all week, carbs at the weekend. The best of both worlds? The one trial says no.
Five or six days of strict keto, then one or two days of loading up on carbs. Bodybuilders swear by it. The only proper trial found it did nothing a normal diet couldn't, and some things worse.
The short version
- What it is
- Keto for five or six days, then one or two high-carb "refeed" days, every week.
- Good for
- People who can't face keto without an escape hatch. Bodybuilding forums.
- Bad at
- Keeping muscle and building strength, in the one proper trial.
- Evidence
- Weak. One small randomised trial.
- Our take
- Not part of our plan. We have a Rebel Day instead, and we don't call it a "refeed".
What cyclical keto actually is
Cyclical keto (CKD, cyclical ketogenic diet) runs in weekly loops. Monday to Friday or Saturday: standard keto, carbs under about 50 g a day. Then one or two days of high-carb eating, often several hundred grams of carbs, to refill the sugar stores in your muscles. Then back to keto.
It came from bodybuilding, where the idea was to lose fat on the keto days and protect muscle and training quality with the refeeds. It's more extreme than targeted keto, which only adds a small carb snack before workouts, and it's a specific form of carb cycling.
How it works in your body
On keto days your body empties its glycogen (stored sugar) and, after a few days, starts making ketones. On refeed days the glycogen comes rushing back, along with the water bound to it. The scale jumps up a kilo or two, then drops again during the week. That's mostly water, not fat.
The catch: getting into ketosis takes a few days, and the refeed throws you straight back out. You keep restarting the hardest part of keto, every single week.
What you eat, what you don't
Eat
- Keto days: eggs, fish, meat, tofu, olive oil, avocado, nuts, greens
- Refeed days: rice, potatoes, oats, fruit, legumes, whole grains
- Protein every day, keto or not
- Vegetables every day
Forget it
- Refeed days as pizza, doughnut and ice cream days
- Sugar, soft drinks, juice
- Carbs sneaking into keto days
- Skipping protein on refeed days
- "Keto" sweets full of sweeteners
A week on cyclical keto
The keto days look like any keto day: eggs and spinach fried in olive oil for breakfast, a big salad with salmon and avocado for lunch, chicken thighs with broccoli and a knob of butter for dinner. Five or six days of that.
A sensible refeed day looks different: oats with a banana and yoghurt in the morning, rice with chicken and vegetables at lunch, potatoes with fish and salad in the evening, fruit in between. Lots of carbs, but from real food, with protein at every meal. An unsensible refeed day looks like a children's birthday party. Guess which one forums post photos of.
Then Sunday night or Monday morning, the carbs stop, and you spend the next two or three days feeling flat while your body hunts for ketosis again.
Cyclical keto in Singapore and in Austria, Germany and Switzerland
Singapore: keto days are easiest at the hawker centre with yong tau foo (no noodles, clear soup), chicken or fish with vegetables, or a mixed vegetable stall without the rice. For refeeds, sliced fish soup with rice or thunder tea rice beat a plate of nasi lemak or a round of kaya toast. Watch the drinks: kopi and teh come sweetened unless you ask for kosong.
Austria, Germany, Switzerland: keto days work with eggs, smoked trout, cheese in normal portions, sauerkraut and salads. On refeed days, boiled potatoes, Bircher muesli without added sugar or rye bread fit far better than Kaiserschmarrn, Brezel and a Sunday cake.
Alcohol on cyclical keto
OK, now and then
- Keto days: spirits neat or with soda water and lime, a glass of dry wine
- Refeed days: one beer or a glass of wine with a meal
Out
- Refeed day as a pub crawl
- Cocktails, liqueurs, sweet wine
- "Zero" mixers: sweeteners are on our never list
- Drinking on an empty stomach
50 Club: one beer with dinner on the relaxed day.
Alcohol pauses fat burning while your liver deals with it: two drinks cut it by about 73% in one study.5 All the details are in our alcohol guide.
What cyclical keto is good for, with proof
Fat loss, the same as a normal diet
The only proper trial we found: 25 healthy young men, eight weeks, both groups eating 500 calories a day less and training. One group did cyclical keto, the other a balanced diet. Both lost about the same body weight and fat.1 So cyclical keto works for fat loss, exactly as well as eating less in a normal way.
A psychological break from keto
For some people, knowing there's a carb day coming makes the strict days bearable. That's real, but there's no study measuring it. Keto in general beat low-fat diets by less than a kilo over a year in a meta-analysis.4 A weekly break won't make that bigger.
The uncomfortable truth
"Cyclical keto protects muscle and performance." In the trial, it did the opposite. The cyclical keto group lost lean body mass, while the balanced-diet group kept theirs. The balanced group also got stronger and fitter on several tests; the keto group didn't improve.1 One small trial, only men, only eight weeks. But it's the only real data, and it doesn't support the bodybuilding legend.
"The refeed resets your metabolism." The best evidence for planned breaks comes from a different set-up. In the MATADOR trial, men with obesity who dieted in two-week blocks, with two weeks of eating at maintenance in between, lost more weight (about 14 vs 9 kg) and more fat than those who dieted non-stop.8 But those breaks were two whole weeks at normal calories, not one carb-heavy day after five days of keto. Nobody has shown that a weekend refeed does the same.
That fits other sports research: strict low-carb, high-fat eating held back performance at high intensity in elite race walkers.2 And the sports nutrition society's position is that fat loss comes down to a sustained calorie deficit, not clever cycles.3
Cyclical keto or a proper diet break?
If what you really want is a break from dieting, there's a better-tested route than weekly carb swings. Our article on refeeds and diet breaks explains the difference: a planned stretch at maintenance calories, instead of a weekly rollercoaster. And it doesn't throw you out of ketosis every Saturday.
The risks
- Lean mass and strength. Lost lean mass and no strength gains in the one trial.1
- Constant keto flu. Going in and out of ketosis every week means more of the tired, foggy transition days.
- Binge-style refeeds. "Carb day" easily becomes "eat everything day". For anyone prone to bingeing, the cycle can feed the problem.
- Diabetes drugs. Swinging between very low and very high carbs makes medication dosing hard. SGLT2 drugs with very low carbs can cause a serious acid build-up.6 Doctor first.
- Keto's long-term risks, like rising LDL cholesterol in some people.4
Allergies: watch the staples
| Staple | Allergen (EU list of 14)7 | Swap |
|---|---|---|
| Eggs | Eggs | Fish, chicken, tofu |
| Cheese, butter, cream | Milk | Olive oil, avocado |
| Nuts, almond flour | Tree nuts | Pumpkin and sunflower seeds |
| Salmon, sardines | Fish | Chicken, eggs |
| Refeed: oats, bread, pasta | Cereals containing gluten | Rice, potatoes, quinoa |
| Refeed: soy milk, tofu | Soy | Rice drink, lentils |
Don't do cyclical keto if you…
- are pregnant or breastfeeding
- have type 1 diabetes, or take insulin or SGLT2 drugs
- have kidney, liver or pancreas disease
- have ever had an eating disorder or tend to binge
- are under 18
Healthen me asks about all of these and gives you a different plan if any apply.
How we use cyclical keto in your plan
We don't. It's an info article for us. The idea of a planned break is good, so we have one: Rebel Day, once a week. Birthday cake, barbecue, eat what you like. The next day is a fasting day.
The rest of the week isn't keto. Your first meal is keto-style, the others are low-carb with real food. If you train hard, carbs move to where the training is, as described in targeted keto.
This article is general information, not medical advice. If you have a medical condition or take medication, talk to your doctor before changing how you eat.
Sources
- Kysel P et al. The influence of cyclical ketogenic reduction diet vs. nutritionally balanced reduction diet on body composition, strength, and endurance performance in healthy young males: a randomized controlled trial. Nutrients 2020;12(9):2832. doi.org/10.3390/nu12092832
- Burke LM et al. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. Journal of Physiology 2017;595(9):2785–2807. doi.org/10.1113/JP273230
- Aragon AA et al. International society of sports nutrition position stand: diets and body composition. Journal of the International Society of Sports Nutrition 2017;14:16. doi.org/10.1186/s12970-017-0174-y
- Bueno NB et al. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. British Journal of Nutrition 2013;110(7):1178–1187. pubmed.ncbi.nlm.nih.gov/23651522
- Siler SQ, Neese RA, Hellerstein MK. De novo lipogenesis, lipid kinetics, and whole-body lipid balances in humans after acute alcohol consumption. American Journal of Clinical Nutrition 1999;70(5):928–936. pubmed.ncbi.nlm.nih.gov/10539756
- US Food and Drug Administration. Drug Safety Communication: FDA warns that SGLT2 inhibitors for diabetes may result in a serious condition of too much acid in the blood, 15 May 2015 (archived copy). web.archive.org: fda.gov/Drugs/DrugSafety/ucm446845.htm Published case series: Mistry S, Cocks Eschler D. Euglycemic diabetic ketoacidosis caused by SGLT2 inhibitors and a ketogenic diet: a case series and review of literature. AACE Clinical Case Reports 2021;7(1):17–19. doi.org/10.1016/j.aace.2020.11.009 (PMC7924151)
- Regulation (EU) No 1169/2011 on food information to consumers, Annex II (the 14 allergens). eur-lex.europa.eu/eli/reg/2011/1169/oj
- Byrne NM et al. Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. International Journal of Obesity 2018;42(2):129–138. doi.org/10.1038/ijo.2017.206