Type 2 diabetes (T2D) is a significant and growing global health concern. The number of people living with diabetes worldwide nearly quadrupled since 1980, with an estimated 422 million cases in 2014. In the USA, the Centers for Disease Control reports that 30.3 million adults presently live with diabetes, a leading cause of death. While treatments for T2D have improved, the condition and related issues like being overweight remain major public health challenges. Dr. Sarah Hallberg, a physician and researcher, has been a vocal advocate for using carbohydrate restriction, particularly ketogenic diets, to manage and potentially reverse T2D. This article examines the Sarah Hallberg diet approach, its scientific basis, and evidence supporting its effectiveness.
Understanding the Sarah Hallberg Diet
The Sarah Hallberg diet is rooted in the principle that reducing carbohydrate intake can significantly improve glycemic control in individuals with T2D. Hallberg advocates for a low-carbohydrate, high-fat (LCHF) dietary approach, often emphasizing nutritional ketosis. Nutritional ketosis, achieved by consuming moderate protein and greatly reduced carbohydrate, results in similarly increased serum beta-hydroxybutyrate (BHB) concentrations as observed during very low energy diets (VLCD), which signifies a shift to using fat as the body’s primary fuel source. Hallberg defines a very-low-carbohydrate or ketogenic diet as less than 50 g of carbohydrates per day, or fewer than 10% of calories consumed. A low-carbohydrate diet is 51-130 g of carbohydrates per day, or 25% or fewer calories consumed; anything above 25% calories consumed is not a low-carbohydrate diet. A well-formulated ketogenic diet, she continues, consists of 5%-10% carbohydrates (or less than 50 g), 15%-20% protein, and 70%-80% fat.
Hallberg often advises patients to avoid "GPS": grains, potatoes, and sugar. She emphasizes the importance of including non-starchy vegetables, nuts, and seeds in moderation.
The Scientific Basis
Hallberg's approach is based on the understanding that carbohydrates have the most significant impact on blood sugar levels. By restricting carbohydrate intake, blood sugar levels can be lowered, reducing the need for medication and potentially reversing the disease's progression. This thinking changed as she studied the war on fat in America. She focused on what happens to food when the fat is removed, discovering that taste is also eliminated. This leads people to eat sweets and carbs. This finding is critical to Type 2 diabetes, because most believe fat should be avoided when fighting the disease. The chronic nature of diabetes care presents an additional challenge requiring sustained behavioral change that is difficult to support with traditional medical care including infrequent provider contact. Adherence to lifestyle changes may be poor in the absence of support from providers and peers.
Glycemic control can be achieved quickly with carbohydrate restriction via very low energy diets (400-800 kcal day−1; VLCD). However, VLCD are necessarily temporary and outcomes often revert when patients resume former dietary patterns. Benefit may accrue from decreased circulating glucose and insulin, ketone signaling, or eventual weight loss.
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Hallberg's Work and Virta Health
Dr. Hallberg is the medical director for Virta Health, a company that provides a technology-enabled, remote-care clinic. Virta's mission is to reverse 100 million cases of Type 2 diabetes without medication by 2025. The intervention utilizes continuous care through intensive, digitally enabled support including telemedicine access to a medical provider (physician or nurse practitioner), health coaching, nutrition and behavior change education and individualized care plans, biometric feedback, and peer support via an online community.
Hallberg also created the Medically Supervised Weight Loss Program at Indiana University Health Arnett and serves as its Medical Director. She is an adjunct Clinical Professor of Medicine at Indiana University School of Medicine.
Evidence Supporting the Approach
Multiple studies support the effectiveness of low-carbohydrate diets, including those promoting nutritional ketosis, in managing and reversing T2D.
Clinical Trial Evidence
Improvement in Glycemic Control: Carbohydrate restriction markedly improves glycemic control in patients with type 2 diabetes (T2D) but necessitates prompt medication changes. In an earlier study, researchers followed 10 inpatients with diabetes in a metabolic ward for 3 weeks. Their mean age was 51 years, and their mean body mass index was 40.3 kg/m2. The patients were fed a standard diet for 7 days, then a low-carbohydrate diet (21 g per day) for 14 days (Ann Intern Med 2005; 142[6]:403-11). After 2 weeks of the low-carbohydrate diet, their mean fasting blood glucose dropped from 7.5 to 6.3 mmol/L, and their mean hemoglobin A1c (HbA1c) fell from 7.3% to 6.8%. Another study randomized patients to a low-carbohydrate ketogenic diet (less than 20 g per day with no calorie restriction) or to a low-glycemic index diet (55% carbohydrate restriction of 500 kcal from baseline) over the course of 24 weeks (Nutr Metab [Lond]. 2008 Dec 19. doi:10.1186/1743-7075-5-36). Between baseline and week 24, the mean HbA1c fell from 8.8% to 7.3% in the very-low-carbohydrate diet group, and from 8.3% to 7.8% in the low-glycemic diet group, for a between-group comparison P value of .03. In addition, 95% of patients in the low-carbohydrate diet group were able to reduce or eliminate the number of medications they were taking, compared with 62% of patients in the low-glycemic diet group (P less than .01).
Weight Loss: In a longer-term trial, researchers evaluated the impact of a ketogenic diet in 64 obese patients with diabetes over the course of 56 weeks (Moll Cell Biochem. 2007;302[1-2]:249-56). The body weight, body mass index, and levels of blood glucose, total cholesterol, LDL cholesterol, triglycerides, and urea showed a significant decrease from week 1 to week 56 (P less than .0001), while the level of HDL cholesterol increased significantly (P less than .0001).
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Medication Reduction: In the overall cohort, the 10-year Atherosclerotic Cardiovascular Disease risk score improved by 12%; almost all markers for cardiovascular disease improved at 1 year. “We were giving these patients appropriate support, which I think is key,” Dr. Hallberg said. “No matter what you do, you have to have a high-touch intervention, and supply that through technology. We do better than medication adherence. Putting patients on a carbohydrate-restricted diet with the appropriate support works for sustainability.” In one study, 95% of patients in the low-carbohydrate diet group were able to reduce or eliminate the number of medications they were taking, compared with 62% of patients in the low-glycemic diet group (P less than .01).
Virta Health Study: We conducted an open-label, non-randomized, controlled, before-and-after 1-year study of this continuous care intervention (CCI) and usual care (UC). Primary outcomes were glycosylated hemoglobin (HbA1c), weight, and medication use. 349 adults with T2D enrolled: CCI: n = 262 [mean (SD); 54 (8) years, 116.5 (25.9) kg, 40.4 (8.8) kg m2, 92% obese, 88% prescribed T2D medication]; UC: n = 87 (52 (10) years, 105.6 (22.15) kg, 36.72 (7.26) kg m2, 82% obese, 87% prescribed T2D medication]. 218 participants (83%) remained enrolled in the CCI at 1 year. Intention-to-treat analysis of the CCI (mean ± SE) revealed HbA1c declined from 59.6 ± 1.0 to 45.2 ± 0.8 mmol mol−1 (7.6 ± 0.09% to 6.3 ± 0.07%, P < 1.0 × 10−16), weight declined 13.8 ± 0.71 kg (P < 1.0 × 10−16), and T2D medication prescription other than metformin declined from 56.9 ± 3.1% to 29.7 ± 3.0% (P < 1.0 × 10−16). Insulin therapy was reduced or eliminated in 94% of users; sulfonylureas were entirely eliminated in the CCI. No adverse events were attributed to the CCI. Additional CCI 1-year effects were HOMA-IR − 55% (P = 3.2 × 10−5), hsCRP − 39% (P < 1.0 × 10−16), triglycerides − 24% (P < 1.0 × 10−16), HDL-cholesterol + 18% (P < 1.0 × 10−16), and LDL-cholesterol + 10% (P = 5.1 × 10−5); serum creatinine and liver enzymes (ALT, AST, and ALP) declined (P ≤ 0.0001), and apolipoprotein B was unchanged (P = 0.37). After 1 year, patients in the CCI, on average, lowered HbA1c from 7.6 to 6.3%, lost 12% of their body weight, and reduced diabetes medicine use. 94% of patients who were prescribed insulin reduced or stopped their insulin use, and sulfonylureas were eliminated in all patients. Participants in the UC group had no changes to HbA1c, weight or diabetes medicine use over the year. These changes in CCI participants happened safely while dyslipidemia and markers of inflammation and liver function improved.
Hallberg's Indiana Type 2 Diabetes Reversal Study
Dr. Hallberg and colleagues are currently in year 4 of the 5-year Indiana Type 2 Diabetes Reversal Study, a prospective, nonrandomized, controlled trial of carbohydrate restriction in 465 patients, making it the largest and longest study of its kind. Of the 465 patients, 387 are in the continuous-care arm, which consists of a diet from Virta Health based on principles of nutritional ketosis, and 87 patients in a usual care arm who are followed for 2 years. The trial includes patients who have been prescribed insulin and who have been diagnosed with diabetes for an average of 8 years.
At the meeting, Dr. Hallberg presented preliminary results based on 2 years of data collection. The retention rate was 83% at 1 year and 74% at 2 years. In the treatment arm, the researchers observed that the level of beta hydroxybutyrate, or evidence of ketogenesis, was the same at 2 years as it had been at 1 year. “So, people were still following the diet, as well as being engaged,” she said.
At the end of 2 years, the mean HbA1c reduction was 0.9, the mean reduction for the Homeostatic Model Assessment of Insulin Resistance was 32%, and 55% of completers experienced reversal of their diabetes. Overall, 91% of insulin users reduced or eliminated their use of insulin, and the average weight loss was 10% of baseline weight.
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Even patients who did not experience a reversal of their diabetes were conferred a benefit. They had an average reduction of 1.2 in HbA1c level, to 7%; their average weight loss was 9.8%; 45% of patients eliminated their diabetes prescriptions; 81% reduced or eliminated their use of insulin; there was an average reduction of 27% in triglyceride levels; and they had a 17% reduction in their 10-year risk score for atherosclerotic cardiovascular disease.
Considerations and Potential Benefits
While the Sarah Hallberg diet and similar low-carbohydrate approaches have shown promise, it's essential to consider certain factors:
Medical Supervision: Blood sugar in patients with T2D can improve quickly when patients eat significantly fewer dietary carbohydrates. However, this demands careful medicine management by doctors, and patients need support and frequent contact with health providers to sustain this way of living. Carbohydrate restriction markedly improves glycemic control in patients with type 2 diabetes (T2D) but necessitates prompt medication changes.
Individualization: Participants were provided individualized nutrition recommendations that allowed them to achieve and sustain nutritional ketosis with a goal of 0.5-3.0 mmol L−1 blood BHB. Behavior change strategies were utilized by the remote care team and tailored to the needs of each participant to help achieve glycemic control. Other aspects of the diet were individually prescribed to ensure safety, effectiveness, and satisfaction, including consumption of 3-5 servings of non-starchy vegetables and adequate mineral and fluid intake for the ketogenic state.
Sustainability: The chronic nature of diabetes care presents an additional challenge requiring sustained behavioral change that is difficult to support with traditional medical care including infrequent provider contact. Adherence to lifestyle changes may be poor in the absence of support from providers and peers.
Potential Benefits: This nutritional therapy may help patients achieve sustainable glycemic control without prescribed energy restriction. Benefit may accrue from decreased circulating glucose and insulin, ketone signaling, or eventual weight loss.