Examining the evidence for use of the ketogenic diet in treating obesity and type 2 diabetes
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Interest in the ketogenic diet and its potential to treat obesity and type 2 diabetes has been steadily growing in recent years. With a very limited amount of calories coming from carbohydrates (typically < 50 gm/day), and the majority of calories coming from fat, this diet leads to a states of physiological ketosis, in which ketone bodies replace glucose as the primary source of energy. Early clinical trials found this to lead to a spontaneous reduction in calories consumed, and it has been suggested that a state of ketosis has appetite suppressing properties. There are a few studies evaluating self-reported decrease in hunger while consuming a ketogenic diet, as well as the changes in hormone levels associated with appetite, but this evidence is limited. The primary determinant of weight change is the difference between calories consumed and calories burned, however there is some suggestion that the macronutrient composition of the ketogenic diet may have a specific metabolic advantage for weight loss separate from the total number of calories in deficit. Multiple diet comparison studies have found the ketogenic diet to be effective for weight loss in the short term, particularly when compared to low fat diets. It is questionable whether the ketogenic diet is sustainable in the long term, particularly without frequent nutritional counseling and monitoring. Still, there is preliminary evidence that the ketogenic diet can lead not only to a large amount of weight loss, but may also be effective in treating and reversing type 2 diabetes. Clinical trials have shown decreases in HbA1c, fasting glucose, and reduction of antiglycemic medication requirements, though it is unclear if these effects are primarily due to weight loss itself, or the specific composition of the ketogenic diet. These benefits need to be weighed against the risks, and a common criticism is its high fat content which can adversely affect serum lipid levels and thus risk of cardiovascular disease. Consuming a ketogenic diet with a high intake of saturated fat has been found to increase LDL cholesterol, however this effect can be mitigated by favoring polyunsaturated or monounsaturated fats instead. While the above findings provide a preliminary understanding of the effects of the ketogenic diet, more research is needed to further elucidate the effectiveness and safety of the diet for treating obesity and type 2 diabetes.