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Low energy and very low calorie ketogenic diets with <50 g of carbohydrates typically result in beta-hydroxybutyrate (BHB) levels >=0.5 mmol within 1-2 days (a common marker of ketosis). It is not known how quickly, or to what extent, people with severe obesity enter in ketosis versus those that are not obese, or that had bariatric surgery.


Eight subjects with severe obesity adhered to 10-day High Protein, Low-Carb, No Fat dietary intervention consisting of four protein shakes and two protein-rich snacks daily (approximately 140g protein, 28g carb, 0g fat = 650-700 kcal/day). Plasma BHB levels were recorded from fingerstick (KetoMojo) each morning after an approximate 12-hour fast. Subjects journaled date and time of protein shakes, snacks, water, and physical activity. Data are presented as mean+-SD.


Subjects were 35.9+-3.8 years with BMI 50.1+-6.3. The baseline fasting BHB level was 0.13+- 0.05 mg/dL. BHB level at Day 10 was 0.59+-0.35 mg/dl (change of 0.46+-0.35mg/dL). Subjects reached the 0.5 mg/dl threshold by 7.0+-1.3 days. Subjects lost an average of 12.3+-5.1 lbs (4.0%+-0.2% of total body weight). Non-obese, sleeve success and failure subjects for comparison remain in enrollment phase.


Subjects with severe obesity required approximately 7-days to enter ketosis when restricted to predominantly high protein diet. This appears to be significantly longer than established timelines in previous research and may have implications for chronic and pre-operative nutritional approaches in severe obesity. Non-obese, sleeve success and failed weight loss cohorts will be compared to subjects with severe obesity when enrollment completes.