June 25, 2020
Question: Can a simple form of dietary restriction, without the use of artificial diets or supplements, rapidly improve glycemic control in diabetics?
Takeaway: This 2019 pilot study found a low-carb, low-calorie diet led to significant weight loss and improvements in glycemic control in diabetic subjects over a 12-week period. These results are consistent with growing evidence indicating diet, unlike standard-of-care methodologies, can reduce the severity of, and even reverse, diabetes.
Growing evidence suggests diabetes is not a lifelong, progressive condition and dietary changes alone can lead to diabetes control and remission (1). As previously discussed on CrossFit.com, low-carbohydrate diets are a specifically promising intervention and have been shown in multiple trials to improve glycemic control, in some cases leading to outright remission (2). Previous research has found a variety of carbohydrate-restricting regimens to be effective, with those involving greater reductions in absolute carbohydrate intake — i.e., a ketogenic diet or a combination of calorie and carbohydrate restriction — leading to greater improvements in glycemic control (3). Most trials involving low-calorie, moderately carb-restricted diets have included artificial diets (e.g., shakes and supplements), which limits their generalizability. This 2019 pilot study specifically tested the impact of a food-based, low-calorie, low-carbohydrate diet on diabetes.
Researchers recruited 33 subjects from primary care practices in Oxfordshire, U.K. All subjects were diabetics with a BMI > 30. Randomization was 2:1, with 21 subjects randomized to the intervention group and 12 to control.
Control subjects maintained usual care (receiving standard dietary advice in line with U.K. guidelines) for 12 weeks. Intervention group subjects were instructed to limit calories to 800-1,000 per day, with less than 26% coming from carbohydrate and a minimum of 60 grams of daily protein (4). To simulate a broadly generalizable program, dietary education and instruction was minimal: four 15-20 minute sessions with a nurse practitioner during weeks two, four, and eight. After following this diet for eight weeks, subjects increased calorie intake to a level that led to weight stability (5).
The intervention group lost an average of 9.5 kilograms over 12 weeks (compared to 2 kilograms in controls). Intervention group subjects improved across a variety of measures of glycemic control including HbA1c (63.2 – 46.9 mmol/mol, 25%), fasting glucose (10.0-7.2 mmol/L, 18%) and fasting insulin (95.1 – 72.9 mmol/L, 23%). All changes were significantly different from both baseline and control; no significant improvements in glycemic control were observed in control group subjects.
Intervention group subjects were on an average of 1.4 anti-diabetes medications and 1.4 antihypertensive medications prior to enrollment. Seven subjects (33%) were able to discontinue at least one medication in each category over 12 weeks. No subjects in the control group discontinued any medication. Notably, subjects in the intervention group cited the desire to reduce or cease medication use as a significant motivating factor for continued compliance. No subjects reported side effects or negative events.
The success of this trial is consistent with a growing body of research indicating non-pharmaceutical, non-surgical interventions can reduce the severity of, or even reverse, diabetes. Given the inability of standard-of-care practices (medication, general dietary advice, surgery) to sustainably reverse diabetes without major side effects, additional research is warranted. Researchers should test the impact of various interventions that improve insulin sensitivity and glycemic control — including carbohydrate restriction and exercise — to broadly and sustainably reverse diabetes.