Intermittent fasting refers to a dietary approach that involves caloric restriction over various intervals of time.1,2 Intermittent fasting has gained increasing attention among the diabetic community as a way to facilitate weight loss and improve glycemic control.
Different Types of Intermitting Fasting
There are numerous types of intermittent fasting. Here are examples of some popular schedules:
- Time-Restricted Feeding: Eating during a 6- or 8-hour window and fasting during the remaining 18- or 16-hour window every day
- Alternate-Day Fasting: Alternating between an eating and a fasting day; modified versions allow consumption of a 500-kcal meal on a fasting day
- “5:2 Diet”: 5 days of eating followed by 2 days of fasting; consumption of a 500-kcal meal is allowed on a fasting day
Mechanism Behind Intermittent Fasting
Studies on animals and humans suggest that after an extended period of fasting (>8-12 hours), the body starts breaking down fatty acids to produce ketone bodies as an alternative source of energy.2 It is suggested that this process activates complex cellular pathways that decrease oxidative and metabolic stress, reduce blood inflammatory markers and free-radical production, and improve glucose regulation, leading to weight loss and cardiometabolic benefits.2,3
Benefits of Intermitting Fasting on Type 2 Diabetes
Although there is a need for more research on the diabetic population, evidence suggests that intermittent fasting has beneficial effects on weight, glycemic control, and insulin resistance among those who are overweight or obese, suggesting that these benefits may be replicated among those with T2DM.4 An umbrella review of 11 meta-analyses of 130 randomized controlled trials (RCTs) found that intermittent fasting may be an effective weight loss approach for individuals who are overweight or obese and that it has significant beneficial associations with various cardiometabolic outcomes (eg, fat mass, low-density lipoprotein and total cholesterol, triglycerides, fasting plasma glucose, fasting insulin, insulin resistance, and blood pressure).4
For instance, a meta-analysis of 11 RCTs found that intermittent fasting improved weight and insulin sensitivity significantly more than continuous energy restriction among overweight or obese individuals.5 A similar meta-analysis of 9 RCTs found that time-restricted feeding significantly improved fasting glucose and insulin resistance measured by the homeostatic model assessment for insulin resistance.6 One RCT compared intermittent fasting to continuous energy restriction among individuals with T2DM and found that both diets were comparable in their effects on glycemic control (measured by reductions in hemoglobin A1C levels) and weight loss over a 12-month period.7
Potential Risks of Intermittent Fasting
Individuals with T2DM should speak with their health care team before starting intermittent fasting.2 Certain populations (eg, pregnant/lactating women, young children, older adults, individuals with immunosuppression, etc.) should be discouraged from intermittent fasting.
Although intermittent fasting is generally considered safe in those with controlled T2DM, they should be aware of the increased risk of hypoglycemia (low blood sugar), especially if taking certain types of (eg, insulin and sulfonylureas). For those on insulin and/or sulfonylureas, regular monitoring and changes to the medication may be needed when initiating intermittent fasting.7 Other potential risks include dehydration and malnutrition, though avoidable through ensuring sufficient fluid and nutrient intake.1
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