When you cut out carbs on a ketogenic diet, you force your body to run on ketones—which come from stored body fat—for fuel. This process, known as ketosis, is extremely effective for getting leaner, and offers a host of other health benefits as well.

The only downside: The first week or so of a ketogenic diet can make you hate life itself. Most keto dieters report feeling deprived, lethargic, and just plain cranky untill their metabolism makes the switch.

In fact, it’s often referred to as the “low-carb flu.”

Fortunately, science has a solution: Ketone-supplying supplements that can smooth your transition to an ultra-low-carb lifestyle and help keep you there—and you won’t have to sacrifice any intensity in the gym in the process. Here, three of our favorite options.