Here’s why. All of these effects take time, but a reasonable explanation as to why the keto diet leads to rapid weight loss is due to the loss of water weight. One of the concerns with the keto diet is the loss of muscle mass and the depletion of glycogen stores. Glycogen, which stores our glucose, also stores water, so when stores are depleted, we flush out excess water. In other words, that rapid weight loss isn’t fat, it’s just water.
And it’s not just this study, either. Several other studies have found  that keto leaves rodents unable to process carbs,[7] leads to insulin resistance,[8] and, more long-term, causes non-alcoholic fatty liver disease, which is when your liver accumulates lots of fat and begins to shut down.[9][10] Triglycerides and inflammation go way up, too.[11]
Difficulty. Many experts question how long a person can realistically give up carbs. “This is a very restrictive diet that requires a drastic change in eating behaviors and even taste,” says Sandra Arevalo, MPH, RDN, CDE, a certified diabetes educator and spokesperson for the Academy of Nutrition and Dietetics. “It isn’t very practical or easy to maintain, for people both with and without diabetes.” That’s not saying you can’t stick with it, but before you commit, make a plan and set measurable goals to help you stay on track. Being prepared with the right foods can also help. Urbanski recommends making a shopping list that focuses on a few basic keto-friendly meals and snacks, so you’ll always have the right foods on hand to ensure success.