The ketogenic diet first gained fame through its effectiveness for weight loss. The high-fat, low-carb diet promotes nutritional ketosis–a normal metabolic state marked by moderate levels of ketones in the blood. The idea with carb restriction in terms of weight loss is that it prompts the release of body fat to be burned or converted to ketones for energy (extra dietary fat also contributes to ketone production).
In many developing countries, the ketogenic diet is expensive because dairy fats and meat are more expensive than grain, fruit and vegetables. The modified Atkins diet has been proposed as a lower-cost alternative for those countries; the slightly more expensive food bill can be offset by a reduction in pharmaceutical costs if the diet is successful. The modified Atkins diet is less complex to explain and prepare and requires less support from a dietitian.
Frederick F. Samaha, M.D., Nayyar Iqbal, M.D., Prakash Seshadri, M.D., Kathryn L. Chicano, C.R.N.P., Denise A. Daily, R.D., Joyce McGrory, C.R.N.P., Terrence Williams, B.S., Monica Williams, B.S., Edward J. Gracely, Ph.D., and Linda Stern, M.D., “A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity,” N Engl J Med 2003; 348:2074-2081. http://www.nejm.org/doi/full/10.1056/NEJMoa022637.
If you can't see any ketones, be patient. It typically takes 2-3 days for your body to deplete glycogen stores, so don't expect to be in ketosis after just a day of low-carb. Remember, ketosis is a favourable condition and an indication that your body uses fat for fuel but you can lose weight even without being in ketosis. A diet high in fat, adequate in protein and low in carbohydrates is naturally sating, making you less hungry and, therefore, helps you lose weight.