A new study out of Australia has identified the flu-like symptoms that arise as a consequence of following the trendy high-fat, low-carbohydrate diet called the ketogenic diet.

General flu-like symptoms were reported by 44.5% of online users. Data from online forums revealed that diet followers identified 54 discrete symptoms from personal experiences, the most common of which were headaches, fatigue, nausea, dizziness, difficulty concentrating, gastrointestinal discomfort, decreased energy, feeling faint and heartbeat alterations. only headaches, difficulty concentrating and gastrointestinal discomfort were reported with more than a 3% frequency by forum users.

Additional symptoms that individuals reported, include feeling faint, heartbeat alterations, sore throat, decreased appetite, shaking, weak fingernails and body aches.

Symptoms appeared between days 3 and 30, with most reports of symptoms arising in the first several days of beginning the diet and reportedly diminishing in strength after the fourth week. Complaints of headaches and weak fingernails continued beyond the four-week period at which point most other symptoms disappeared.

Researchers relied on posts from English-language online forums to characterize the symptoms, severity, time course and remedies proposed by users for the “Keto Flu.” Overall, 43 online forums with 300 unique users comprised the data used in this study. Out of all the entries collected, one third of the identified users had personal experience with the keto flu. 

The study concluded that the findings “suggest that the physiological and perhaps psychological changes associated with ketogenic diet result in the manifestation of an induction and adaptation related syndrome.” However, it remains unclear whether the “Keto Flu” is an “illness state” due to nutritional or immune imbalance or if it is “indicative of an adaptive bodily process.” Keto-adaptation is a corporal state that experts hypothesize requires several weeks to multiple months for the body to reach an adequate and stable level of ketones. Ketones are an alternative fuel source for the body produced from fat in the liver; their production is triggered when a body’s sugar levels are low. 

The “keto” diet, as the ketogenic diet is known in popular culture, has been a medical diet since the 1920s when it was used to treat epilepsy. Today, it is promoted as a solution for weight loss, memory enhancement, type II diabetes treatment, migraine relief and an adjuvant therapy for cancer patients. Other than epilepsy, there is limited scientific evidence for the health benefits that are attached to following the ketogenic diet.