The biggest problem with using any of the ketogenic diets is that they are very unforgiving if you eat too much of things you shouldn’t. Most diets have calorie-based rules, so when you cheat on your diet, you don’t lose as much weight as you would like.
When you cheat while on a ketogenic diet, it changes your metabolic process and all ketone production stops until the process recovers, if it does at all. See: “What are the rules for ketogenic diets?” and “What happens to the body during keto?” for more information. This has a huge impact on the ability to lose weight on a keto diet.
As an evolutionary safety net, ketosis is the metabolic process that our body switches to when there aren’t enough carbohydrates available to us. See: “What is dietary ketosis” for a brief discussion of ketosis.
The body doesn’t know WHY the carbohydrates aren’t available, only that there are not enough available, so it switches to ketones (derived from fat) for fuel. Ketogenic diets take advantage of this to burn our own fat for fuel.
Every single gram of carbohydrate ingested decreases the body’s need for ketosis. If you ingest enough carbohydrates, the entire process stops and reverts back to a carbohydrate-based metabolism.
Everyone’s metabolism is different, but the general consensus is that <20 grams of net carbohydrates per day will keep you in ketosis enough of the time to burn your own fat stores almost continuously.
When you get to around 50 grams per day, your body fluctuates in and out of ketosis allowing you to maintain your current weight, but not burning much body fat.
>100 grams of carbohydrates a day will almost definitely kick you out of ketosis altogether, although there is a little leeway if carbs are evenly distributed through out the day.
If you cheat before you have completed the Transition Phase (see “What happens to the body during keto?”), you may have to start the Induction Phase all over. In fact, some people who think they are doing a ketogenic diet never actually reach optimized ketosis.
That is the main reason for not achieving weight loss while on the diet. See “I’m in ketosis. Why am I not losing weight?” for further discussion.
Yo-yo dieting is not possible while on a ketogenic diet. You can’t be on it one day, off the next and then back on it again. The back and forth will keep you out of optimal ketosis and the amount of fat you eat will be stored as body fat since it isn’t being burned for fuel.
Under these conditions, you are likely to not only gain weight, but mess up your blood cholesterol levels, blood lipid (fat) levels, and increase your risk for conditions related to high-fat diets. Ketogenic diets are more of an all-or-nothing proposition than any other diets for this reason.
However, it is possible to have a cheat day and not completely throw away all of the progress you’ve made. This assumes that you are already in optimal ketosis (after Transition Phase) and that your cheat is limited in the amount of carbs or number of cheat meals consumed.
In effect, if you have a cheat meal or even a cheat day, you can recover from it. For information on how to get back into ketosis after a cheat day, see “How can I get back into ketosis after a cheat day?”.
In summary, cheating on a ketogenic diet can be an emotionally gratifying way of attacking cravings, but if not correctly done, it can ruin your diet and possibly lead to health risks due to elevated blood cholesterol and blood lipids.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.