A review of the effectiveness of low-carbohydrate diets in controlling plasma glucose and resulting in other positive health outcomes in patients with type 2 diabetes mellitus
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Low carbohydrate diets have been studied for many years as nutritional therapy for treating patients with type 2 diabetes mellitus (T2DM). Type 2 diabetes is an inflammatory disease that is defined by high blood glucose and HbA1c, lipid levels, BMI, central adiposity, and cholesterol levels, are some among the many indicators that can signal risk for diabetes or help to diagnose diabetes. These indicators are used in studies to evaluate the effectiveness of the nutritional therapy in producing positive health outcomes. Many medications are available for the treatment of T2DM; however, they have a host of side effects, and nutritional therapy has been shown to at least help reduce the dosage of these medications needed by the patients. There are other forms of nutritional therapy besides low carbohydrate diets, and some controversy remains about low carbohydrate diets that in the long term, replacing carbohydrates with fats and proteins could result in increased cholesterol and lipid levels, creating an increased risk for cardiovascular disease. Although some studies have found that low carbohydrate diets, especially very low carbohydrate ketogenic diets (VLCK), do result in increased cholesterol, it is generally an increase in HDL, which is considered good cholesterol and not harmful. Overall weight loss benefits from reduced central adiposity, BMI, and reduced HbA1c levels outweigh the increase in HDL as a side effect. A few different variations of low carbohydrate diets are compared in this review, such as very low carbohydrate ketogenic diets, moderate carbohydrate calorie restricted diets, and moderate carbohydrate low (MCD) Glycemic Index (GI) diets. Due to the ability to exchange carbohydrates with high GI for carbohydrates with low GI, the MCD with low GI sounds promising for good adherence and positive health outcomes in the long run. Although very low carbohydrate ketogenic diets produce many positive health outcomes, the nutritional therapy must be very well designed and followed up, and care must be taken that fiber and nutrients are maintained in the diet. Adherence is a key part of the success of nutritional therapy and a study design plays a major role in that. Providing behavioral development classes, nutritional information classes, and intermittent classes focused on physical activity and healthy habit formation leads to overall increased positive affect which is better for the patient and thus, for the study as well. The easier the nutritionist or dietician can make the therapy transition for the participant, the more likely they are also to stay and try to stick with it. For example, in the studies where the study coordinator provided some small food provisions at the beginning or throughout the study seemed to be successful because the patients were less likely to fall to making their own choices poorly and being inconsistent. Although there were many diets that resulted in many positive health outcomes, ultimately a well-designed, adherence focused, very low carbohydrate ketogenic diet seemed to be the most effective at decreasing HbA1c and producing other positive health outcomes as well. In the long term however, a VLCKD, may be unsustainable for the patient and the body, given the extreme reduction in important carbohydrates.