On the ketogenic diet, carbohydrates are restricted and so cannot provide for all the metabolic needs of the body. Instead, fatty acids are used as the major source of fuel. These are used through fatty-acid oxidation in the cell's mitochondria (the energy-producing parts of the cell). Humans can convert some amino acids into glucose by a process called gluconeogenesis, but cannot do this by using fatty acids. Since amino acids are needed to make proteins, which are essential for growth and repair of body tissues, these cannot be used only to produce glucose. This could pose a problem for the brain, since it is normally fuelled solely by glucose, and most fatty acids do not cross the blood–brain barrier. However, the liver can use long-chain fatty acids to synthesise the three ketone bodies β-hydroxybutyrate, acetoacetate and acetone. These ketone bodies enter the brain and partially substitute for blood glucose as a source of energy.
Make things yourself. While it’s extremely convenient to buy most things pre-made or pre-cooked, it always adds to the price per pound on items. Try prepping veggies ahead of time instead of buying pre-cut ones. Try making your stew meat from a chuck roast. Or, simply try to make your mayo and salad dressings at home. The simplest of things can work to cut down on your overall grocery shopping.
I want to give special mention one of the side effects of carb withdrawal because it can really be scary if you don't know what it is. During the first week or so of cutting your carb intake, your blood sugar levels will fall, and you may experience a mild insulin overload and reactive hypoglycemia. This usually happens to people who are severely insulin resistant. It takes about 2-3 days to burn through all of your stored glycogen (carb energy stored in your muscles and liver), and after that you may get these low blood sugar symptoms of shakiness, dizziness, tremors, a pounding heart and more. (See the link above for more info). For those of you that have been living on a high-carb diet for a long time, the effects may be even more pronounced, as your blood sugar and insulin levels are probably chronically high.
There are so many tricks, shortcuts, and gimmicks out there on achieving optimal ketosis – I’d suggest you don’t bother with any of that. Optimal ketosis can be accomplished through dietary nutrition alone (aka just eating food). You shouldn’t need a magic pill to do it. Just stay strict, remain vigilant, and be focused on recording what you eat (to make sure your carb and protein intake are correct).