Counting Hours, Not Carbs: The Intermittent Fasting Approach to Controlling Diabetes
Intermittent fasting is shown to regulate blood sugar and promote weight loss
Intermittent Fasting is an increasingly popular dietary approach that has surpassed the ketogenic (high-fat) diet as the "most popular" diet in the United States. Around 10% of Americans between the ages of 18-80 reported adhering to some form of intermittent fasting. Broadly speaking, it involves cycling between periods of fasting and eating, such as time-restricted eating (only eating within a defined window each day) or alternate-day fasting. Intermittent fasting has been associated with weight/fat loss, improved cholesterol and insulin sensitivity, blood sugar control, and reduced inflammation.
After metabolic testing revealed pre-diabetes alongside high triglyceride levels, and with a longstanding desire to achieve a healthier weight, I committed to adopting the diet in the summer of 2019. Since then, I've shed over 35lbs, and my triglyceride levels have dropped from 352 in March 2019 to 93 now, representing an almost 75% reduction. Furthermore, HbA1c1 levels were lowered by more than 5%. Skipping breakfast, I start eating only at 12 noon and "stop" eating by 6PM. While I manage this schedule successfully on most nights, resisting a late-night snack while streaming a show has proven to be quite challenging. Starting my day with black coffee and winding down with sparkling water at night has been reasonably effective in subduing my hunger pangs.
Effect of Intermittent Fasting on my triglyceride levels
Effect of Intermittent Fasting on my HbA1c levels
Unfortunately, intermittent fasting does not equate to unrestricted calorie consumption, a detail I occasionally tend to overlook. It's crucial to not only limit calories but also maintain a balanced ratio of protein, fats, and carbohydrates.
Time-Restricted or Calorie-Restricted?
This review paper cites multiple studies demonstrating that intermittent fasting is effective at reducing body weight, fasting glucose, fasting insulin, insulin resistance, leptin levels, and increasing fat-burning adiponectin levels in type 2 diabetes patients. For example, a JAMA randomized clinical trial by Varady et al. compared an 8-hour time-restricted diet with a calorie-restricted diet in 75 adults with Type 2 diabetes and obesity. After 6 months, the time-restricted eating group lost around 10 pounds on average, nearly twice as much as the calorie-restricted group (6 pounds). Both groups saw about a 1 point drop in HbA1c levels, from around 8% to 7%. This suggests that time-restricted eating may be an effective alternative strategy to calorie-restricted diet for lowering body weight and HbA1c levels in Type 2 diabetes patients. Another randomized controlled trial investigated intermittent fasting over 12 weeks in 46 people with insulin-treated Type 2 diabetes. The intermittent fasting group showed a significant reduction in HbA1c compared to the control group. 8 participants in the fasting group achieved the composite endpoint of ≥2% weight loss, ≥10% insulin dose reduction, and HbA1c reduction, compared to none in the control group. An ongoing pilot clinical trial at University of Illinois, Chicagois planning to explore if intermittent fasting is safe for patients with Type 1 diabetes. This ongoing pilot study is examining how time-restricted eating compares to calorie counting in 60 participants with type 1 diabetes. The aim is to assess if time-restricted eating is safe and effective for improving glycemic control in type 1 diabetes patients. Results are expected in February 2025. Clearly, there is ample evidence that intermittent fasting regimens lead to weight loss, improved glycemic control (reduced HbA1c), decreased insulin resistance, and potentially diabetes remission in both Type 1 and Type 2 diabetes patients.
How Does Fasting Reduce HbA1c Levels?
There has been considerable research in understanding the exact pathways through which fasting reduces HbA1c levels. Intermittent fasting leads to the activation of AMP-activated protein kinase (AMPK), which increases fat oxidation (the process by which the body breaks down fats (triglycerides) into smaller molecules, such as free fatty acids and glycerol, which is then be used as a source of energy) and glucose uptake in muscle cells. Glucose uptake in skeletal muscle and fatty acid oxidation are both critical metabolic processes that provide energy for the body, help maintain glucose homeostasis, and contribute to overall metabolic health. Dysregulation of these pathways leads to the development of metabolic diseases such as diabetes.
During fasting, the body shifts from glucose utilization to leveraging of fatty acids and ketone bodies as primary energy sources. This metabolic shift reduces the reliance on glucose, thereby lowering blood glucose levels and subsequently HbA1c. The body's increased reliance on "breaking down of fats" over "creation of fats" also contributes to this effect. Intermittent fasting also results in weight loss and a reduction in visceral fat (fat that wraps around organs in your belly that are deep inside). This decrease in body fat leads to improvements in insulin resistance and lower HbA1c levels. The reduction in body weight is associated with less strain on the body's ability to manage glucose, which directly impacts HbA1c levels. Finally, intermittent fasting can result in shifts within the gut microbiome, including an increase in the variety of different types of microorganisms present. For example, the anaerobic bacteria family Lachnospiraceae has been observed to flourish during fasting periods. This increase in microbial diversity is considered beneficial, as higher diversity is associated with improved metabolic health and reduced risk of diseases. In summary, these pathways collectively contribute to the reduction of HbA1c levels through various metabolic, hormonal, and physiological changes induced by intermittent fasting.
Recently, a study presented at the American Heart Association conference in March 2024, found that people who followed an 8-hour time-restricted eating pattern had a 91% higher risk of dying from cardiovascular disease compared to those who ate over a 12-16 hour period. The study involved over 20,000 adults in the U.S. and followed them for an average of 8 years. The study suffers from several limitations, including lack of a peer review, and participants' self-reported data about their eating patterns, which can be inaccurate. The study did not provide details about the participants' underlying health conditions, physical activity levels, BMIs, and other important factors that influence cardiovascular risk. Furthermore, it did not examine what participants were eating during their 8-hour eating window, whether they were consuming healthy, balanced meals or unhealthy, processed foods. Experts have emphasized the need for more rigorous, long-term research to better understand the potential risks and benefits of intermittent fasting, especially regarding its impact on cardiovascular health. The study, while raising important questions, has significant limitations that prevent making firm conclusions at this stage.
Takeaway: Emerging evidence (and my personal experience) suggests that intermittent fasting regimens lead to weight loss, improved glycemic control with reduced HbA1c levels, decreased insulin resistance, and potentially diabetes remission in both Type 1 and Type 2 diabetes patients. Optimal outcomes are observed when fasting is complemented by calorie restriction.
HbA1c, or glycated hemoglobin, measures the average amount of glucose attached to hemoglobin, the oxygen-carrying protein in red blood cells. Higher HbA1c levels (6.5% or higher) are associated with an increased risk of diabetes complications like nerve damage, kidney disease, and vision loss.