Abstract
Type 2 diabetes mellitus (T2DM) is a growing global health concern, prompting exploration of various therapeutic strategies, including dietary interventions. Fasting, characterized by periods of voluntary abstinence from food, has emerged as a promising approach for managing T2DM. This review examines the efficacy of different fasting protocols in improving blood glucose levels and insulin sensitivity in individuals with T2DM, providing current perspectives on their potential as a therapeutic tool.
Introduction
Dietary intervention is a commonly used therapeutic measure for patients with type 2 diabetes mellitus (T2DM), and it is also the simplest, most effective, and most cost-effective intervention[1]. As the prevalence of T2DM continues to rise, so does the exploration of nutritional therapies, such as fasting, to improve glycemic control and overall metabolic health[2]. Prolonged caloric restriction can lead to poor patient compliance[1]. Intermittent fasting (IF), as a new dietary intervention, differs from the traditional calorie restriction (CR)[1]. This review synthesizes the current evidence on the effects of various fasting protocols on blood glucose management and insulin sensitivity in individuals with T2DM.
Fasting Protocols for T2DM Management
- Time-Restricted Eating (TRE):
- TRE involves limiting eating to a specific window of time each day, typically ranging from 4 to 10 hours[1].
- Studies show that TRE can significantly improve glycemia and insulin resistance in patients with T2DM[1]. TRE divides the day into periods of fasting and periods of eating, and the length of fasting is usually 14–16 h[1]. For example, in an eight-hour plan, an individual might eat from 10 a.m. to 6 p.m. and then not again until the next day at 10 a.m.[3].
- An increase in fasting duration improves fasting glucose values in patients with T2DM[1].
- Alternate-Day Fasting (ADF):
- ADF involves alternating between days of normal eating and days of either complete fasting (zero-calorie ADF) or severe calorie restriction (consuming 0–25% of daily caloric needs)[1].
- If you have type 1 or 2 diabetes, you can do alternate day fasting under the close supervision of your doctor[3].
- Twice-Per-Week Fasting (TWF):
- TWF is a modified version of ADF that involves fasting for two days per week, which can be consecutive or non-consecutive[1].
- The SUCRA results showed that patients with T2DM on TWF had the best combined effect in improving fasting glucose and insulin resistance compared to other IF regimens, and therefore it has the greatest potential to be the optimal IF regimen[1]. TWF requires people to follow a very low-calorie diet for only two days of the week, and the rest of the week they do not have to adhere to a strict restriction of calorie intake, which is a significant improvement over other restrictive dietary behaviors[1].
- For patients with inter-type 2 diabetes, twice-per-week fasting intervention has a good effect and can be used as a reference for choosing an intermittent fasting regimen. However, more clinical trials are needed to verify this at a later stage[1].
- Periodic Fasting (PF) and Fasting-Mimicking Diets (FMD):
- PF involves prolonged periods of severe calorie restriction or water-only fasting, ranging from 48 hours to one week, usually every two weeks[1].
- FMD is a specially formulated, calorie-restricted, five-day nutritional program[1].
Efficacy of Fasting Protocols on Blood Glucose and Insulin Sensitivity
- Glycemic Control:
- Intermittent fasting may reverse type 2 diabetes[5].
- Intermittent fasting therapy, as a new dietary intervention mode, has certain advantages in the treatment of T2DM, especially TWF[1].
- The SUCRA results showed that in addition to TWF, TRE also significantly improves glycemia in patients with T2DM[1]. An increase in fasting duration improves fasting glucose values in patients with T2DM[1].
- Insulin Sensitivity:
- Published research assessing the effect of fasting in T1DM has demonstrated positive outcomes, including a reduced need for exogenous insulin, stabilization of glycemia, a reduction in body weight and body mass index (BMI), and lower total carbohydrate intake[2].
- The present results show that TWF has a better overall effect on improving insulin sensitivity and therefore can be a preferred option for dietary intervention in patients with T2DM[1].
- TRE has also shown better results in improving insulin sensitivity[1].
Practical Considerations and Guidelines
- Medical Supervision: Fasting can be safely undertaken in patients with diabetes when done under the supervision of the patient’s healthcare provider, and with appropriate personal glucose monitoring[4]. Your doctor may adjust your medication schedule and dosages and give you instructions on how frequently to check your blood sugar[3].
- Individualized Approach: Clinicians or dietitians can help patients with T2DM understand and co-develop an appropriate IF program[1].
- Gradual Increase: Patients are advised to gradually increase the duration and frequency of fasting over a period of several months and should consult a dietitian about the applicability and limitations of their use of dietary interventions before proceeding with IF treatment in order to tailor the optimal IF intervention for each individual[1].
- Lifestyle Integration: For individual patients, a pattern of fasting that is most easily integrated into their lifestyle should be chosen to reap the benefits of long-term fasting[1].
Limitations and Adverse Effects
- Adverse Effects: Adverse effects were only mentioned in one study. This may be due to impaired mitochondrial fatty acid oxidative energy supply as a result of the reduction of free L-carnitine during fasting, and it was hypothesized that the addition of L-carnitine analogues during fasting may reduce the incidence of adverse effects[1].
- Risk of Hypoglycemia: Fasting has the potential to minimize the risk of hypoglycemia in T1DM[2]. However, caution is needed.
Conclusion
Fasting protocols, particularly TRE and TWF, show promise as therapeutic interventions for managing blood glucose levels and improving insulin sensitivity in individuals with T2DM. Intermittent fasting therapy, as a new dietary intervention mode, has certain advantages in the treatment of T2DM, especially TWF[1]. However, given the limitations of current studies, clinical staff should formulate the optimal dietary program in accordance with the patients’ actual conditions and dietary habits to improve treatment compliance[1]. With proper medical supervision, individualized planning, and attention to potential adverse effects, fasting can be a valuable tool in the management of T2DM. In future studies, the time window and caloric range should be further refined to provide an effective, non-drug intervention for the clinical treatment of T2DM patients[1].
Citations:
[1] https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2024.1325894/full
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC10459496/
[3] https://www.webmd.com/diabetes/fasting-diabetes
[4] https://pmc.ncbi.nlm.nih.gov/articles/PMC6521152/
[5] https://www.endocrine.org/news-and-advocacy/news-room/2022/intermittent-fasting-may-reverse-type-2-diabetes
[6] https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2820237
