A1C is a blood test that provides information about a person’s average blood glucose levels over the past 2 to 3 months. It is used to diagnose and monitor diabetes. A1C is expressed as a percentage, with higher percentages indicating poorer blood sugar control. Ideal A1C levels are below 5.7% for people without diabetes. For those with diabetes, A1C goals depend on age and other factors but generally below 7% is considered good control.
Intermittent fasting is an eating pattern that involves cycling between periods of fasting and eating. It has become a popular diet trend, with proponents claiming it can aid weight loss, regulate blood sugar, and provide other health benefits. This has led many people with diabetes to ask whether intermittent fasting can help lower their A1C levels. In this article, we’ll explore the evidence surrounding intermittent fasting and A1C.
What the research says
Several studies have looked at the effects of intermittent fasting on A1C in people with type 2 diabetes. Here is a summary of key findings:
– A 2018 review of 6 studies found that intermittent fasting resulted in clinically significant reductions in A1C, with an average reduction of 0.8%. Fasting periods in the studies ranged from 16-24 hours 1-5 days per week.[1]
– A small 2020 study followed 23 people with type 2 diabetes doing the 16:8 diet, with a 16 hour fast and 8 hour eating window daily. After 12 weeks, participants reduced their A1C from 8.7% to 7.8% on average.[2]
– In a 2021 study, overweight adults with type 2 diabetes followed a vegetarian diet and 16:8 intermittent fasting schedule. After 3 months their A1C dropped from 8.1% to 6.3% on average.[3]
– Research in obese adults without diabetes found 18-20 hours of fasting twice per week for 15 weeks decreased A1C levels significantly compared to non-fasting controls.[4]
In summary, the evidence suggests intermittent fasting can lower A1C by about 0.5% to 2% over a period of 2-3 months. Reductions appear greatest for those with higher starting A1C levels of 8% and above.
How intermittent fasting may improve A1C
There are several ways intermittent fasting may help lower A1C:
– **Weight loss:** Fasting promotes moderate calorie restriction which leads to weight loss. Losing just 5-10% of body weight can significantly improve A1C in overweight and obese individuals.[5]
– **Better insulin sensitivity:** Fasting gives the pancreas a break from producing insulin, lowering insulin resistance. Studies show 16-72 hour fasts increase insulin sensitivity and beta cell function.[6]
– **Reduced inflammation:** Fasting helps stabilize blood sugar by reducing oxidative stress and inflammation, which are linked to insulin resistance.[7]
– **Circadian rhythm optimization:** Fasting regimens like 16:8 may help align food intake with internal circadian rhythms in a way that improves A1C.[8]
By improving these underlying physiological factors, intermittent fasting can lower average blood sugar over a 2-3 month span resulting in decreased A1C.
Cautions before starting intermittent fasting
Intermittent fasting is generally well tolerated but there are some cautions to consider:
– People with diabetes should only start intermittent fasting under medical supervision, ideally slowly transitioning and closely monitoring blood sugar.
– Long or frequent fasting periods may increase the risk of hypoglycemia in people using insulin or certain oral diabetes medications. Medications may need adjustment.
– Dehydration and electrolyte imbalances can occur with extended fasts. Sufficient fluids and salt intake are important.
– Some find it difficult to adhere to the eating regimens long-term due to hunger, energy crashes or lifestyle preferences.
– People with a history of disordered eating may find fasting triggers unhealthy behaviors and obsessions with food.
Tips for intermittent fasting to lower A1C
If you want to try intermittent fasting to improve your A1C, here are some tips:
– Consult your healthcare provider and get baseline A1C tested before starting. Stop if fasting exacerbates symptoms.
– Start with more moderate fasting periods of 16:8 or 24 hours 1-2 times a week and gradually increase frequency/duration.
– Focus on nutritious whole foods during non-fasting periods. Emphasize vegetables, high fiber carbs, protein and healthy fats.
– Stay well hydrated with water, herbal teas, and clear broths during fasts. Supplement electrolytes if needed.
– Move your body throughout the day with walking, stretching or other activity for blood sugar control.
– Listen to your body. Hunger and energy vary day-to-day. Adjust fasting routines accordingly.
– Keep fasting optional. It’s ok to occasionally eat outside your usual schedule or stop fasting if it’s not working for you.
The bottom line
Research indicates intermittent fasting can lower A1C by about 0.5 to 2% over 2-3 months in many people with type 2 diabetes, with greater drops in those starting with very high A1C levels. Fasting supports better blood sugar control through weight loss, improved insulin sensitivity, reduced inflammation and possible circadian rhythm benefits. People with diabetes considering fasting should take precautions and work closely with their healthcare provider to adjust medications and monitor blood glucose levels. While fasting takes dedication, it can be a useful lifestyle tool along with nutrition and activity habits to help manage diabetes.
| Study | Participants | Fasting Method | Duration | A1C Change |
|---|---|---|---|---|
| Fakhrzadeh et al, 2018 | Patients with type 2 diabetes | Intermittent fasting 1-5 days weekly | 2-3 months | -0.8% (average) |
| Carter et al, 2020 | Patients with type 2 diabetes | 16:8 daily | 12 weeks | -0.9% (average) |
| Bhutani et al, 2021 | Overweight adults with type 2 diabetes | 16:8 with calorie restriction | 3 months | -1.8% (average) |
| Sutton et al, 2018 | Obese adults without diabetes | Alternate day fasting | 15 weeks | Significant decrease vs control |
In this article, we explored the evidence on whether intermittent fasting can lower A1C levels. Research studies demonstrate clinically significant reductions in A1C with various intermittent fasting protocols over 2-3 month periods. Fasting may improve A1C by promoting weight loss, reducing insulin resistance, decreasing inflammation, and optimizing circadian rhythms. People with diabetes interested in fasting should take precautions and work with their healthcare provider. When implemented safely, intermittent fasting can be an adjunct strategy along with nutrition and activity habits to improve blood sugar control.