The ketogenic (or keto) diet is commonly known for its effect on weight loss. However, it was once developed for its beneficial effect in patients with epilepsy. Nowadays, the keto diet is also used to treat other pathologies like type 2 diabetes and cardiovascular disease. But, how tolerant is this ketogenic diet to cheat days?
The diet typically consists of eating products very low in carbohydrates, but high in fats, which causes the body to go into a state called ketosis. During ketosis body-own fat as well as so called “keto-bodies” (some type of ‘super fuel’ which is being produced in the absence of carbohydrates) are the main suppliers of energy. As fat metabolism increases, body fat percentage typically drops when eating keto.
In general, a ketogenic diet draws 70% of its energy from fat, 10% from carbs which leaves a remaining 20% for proteins. In practical terms, this type of diet - like any diet - is quite difficult to strictly hold on to in the long run, due to it's restrictive character. And that's why experienced “dieters” probably implemented “cheat days” so now and then. A cheat day can be described as a day where you can have some extra comfort food and enjoy the good life. Meaning: less restrictions and space for items that are usually not allowed. We are oftentimes being told that the positive thing of such days is that, they ease persistence.
"People on a keto-diet may undo some of the positive impacts on their blood vessels if they suddenly blast them with glucose."
However, a recent study indicated a negative effect of cheat days during a ketogenic diet on several biological parameters such as blood markers. It appeared that the sudden spike in glucose after the consumption of carb-rich products resulted in substantial damage on the vessel walls. It is well known that long-term high-carb loading affects vessel condition and could lead to cardiovascular disease.
Based on these findings, researchers worry that “people on a keto-diet - either to lose weight or to treat diabetes - may undo some of the positive impacts on their blood vessels if they suddenly blast them with glucose. Especially when at higher risk for cardiovascular disease in the first place”
So in conclusion, a ketogenic diet is not something you do for 5 or 6 days a week, and take a weekend off. Up to you to embrace a lifestyle as a whole or just go for the quick fix.
C. Durrer, N. Lewis, Z. Wan, et al. Short-Term Low-Carbohydrate High-Fat Diet in Healthy Young Males Renders the Endothelium Susceptible to Hyperglycemia-Induced Damage, An Exploratory Analysis. Nutrients, 2019; 11 (3): 489