Who benefits from intermittent fasting, and how much?
People with type 2 diabetes who are overweight or on oral medications may see the biggest improvements. In a randomized controlled trial of 72 adults with type 2 diabetes, 47% of those who followed an intermittent fasting diet achieved diabetes remission (HbA1c below 6.5% off all diabetes drugs for at least 3 months), compared to just 2.8% in the control group [2]. That means nearly half the people in the fasting group were able to stop their diabetes medications entirely, at least temporarily.
Even people who need insulin can benefit. In a 12-week trial of 46 insulin-treated adults, those who fasted three non-consecutive days per week saw their HbA1c drop by an average of 0.7% (from about 7.5% to 6.8%), while the control group saw no change [3]. Importantly, this was achieved while reducing total daily insulin doses by at least 10% in many participants, and no severe hypoglycemia occurred [3].
Weight loss is a consistent bonus. Across studies, people lost an average of 5–6 kg (11–13 lbs) over 3–6 months [2][1]. In one study, weight loss was directly linked to the number of fasting days [4]. Even modest weight loss of this size can improve insulin sensitivity and reduce diabetes complications over time.
What are the risks, and how do you stay safe?
The main risk of intermittent fasting for people with type 2 diabetes is low blood sugar (hypoglycemia), especially if you take insulin or sulfonylurea pills. In the insulin-treated trial, researchers carefully reduced insulin doses on fasting days and monitored glucose continuously, which prevented severe hypoglycemia [3]. Without those adjustments, the risk would be much higher. A review of the evidence emphasizes that safety monitoring is critical, particularly for insulin users [5].
Other side effects are common but usually mild and temporary. In a large trial of 209 adults at risk for diabetes, people in the fasting group reported more fatigue, constipation, and headaches than those on standard care [1]. These effects often improve after the first few weeks as the body adapts.
Not all forms of fasting are equal for blood sugar control. One study found that while Ramadan fasting (daylight hours for a month) improved weight and inflammation markers, it caused a temporary rise in fructosamine (a short-term blood sugar marker), suggesting that glycemic control can worsen during the fast itself [4]. This means the type and timing of fasting matter, and glucose should be checked more often during fasting periods.
How should someone with type 2 diabetes start intermittent fasting?
Start only after consulting your doctor or diabetes educator, who can adjust your medications (especially insulin and sulfonylureas) to prevent lows. The most studied approach in these trials is fasting on 3 non-consecutive days per week, eating only between 8 a.m. and 12 p.m. on those days (a 20-hour fast), and eating normally on other days [1][3]. This pattern improved glucose tolerance more than daily calorie restriction in one study [1].
Expect to check your blood sugar more often, especially on fasting days. Continuous glucose monitors (CGMs) can make this easier and safer [5]. Many people find that their insulin needs drop significantly within the first few weeks, so medication adjustments are often needed quickly.
Results can be substantial but may not last forever. In one study, the blood sugar improvements seen at 6 months were no longer different from the calorie-restriction group by 18 months, suggesting that long-term adherence is key [1]. However, another study found that 44% of people who achieved remission maintained it for at least 12 months [2]. The bottom line: IF can be a powerful tool, but it works best as part of a sustained lifestyle change, not a quick fix.
About These Sources
This answer is built on 5 peer-reviewed studies — published from 2022 to 2025, 1 from 2024 or later, 3 in Q1 journals, collectively cited 178 times — selected as the most relevant from 6 studies that passed quality screening, drawn from 35 papers retrieved from a database of over 500 million.
Sources used in this answer
Intermittent fasting plus early time-restricted eating versus calorie restriction and standard care in adults at risk of type 2 diabetes: a randomized controlled trial
In a randomized controlled trial of 209 adults at risk for type 2 diabetes, intermittent fasting with early time-restricted eating (3 days/week, 20-hour fasts) improved glucose tolerance more than daily calorie restriction at 6 months, but the difference was lost by 18 months; side effects included fatigue, constipation, and headache.
Effect of an Intermittent Calorie-restricted Diet on Type 2 Diabetes Remission: A Randomized Controlled Trial
In a randomized trial of 72 adults with type 2 diabetes, 47% of those on an intermittent fasting diet achieved diabetes remission (HbA1c <6.5% off medications for ≥3 months) vs. 2.8% in controls; 44% maintained remission at 12 months, and medication costs dropped 77%.
Efficacy and Safety of Intermittent Fasting in People With Insulin-Treated Type 2 Diabetes (INTERFAST-2)-A Randomized Controlled Trial.
In a 12-week randomized trial of 46 insulin-treated adults with type 2 diabetes, intermittent fasting (3 non-consecutive days/week) reduced HbA1c by 0.7% and allowed insulin dose reduction without any severe hypoglycemia, confirming safety and feasibility.
Impact of Ramadan intermittent fasting on metabolic and inflammatory profiles in type 2 diabetic patients
In a prospective study of 55 type 2 diabetes patients observing Ramadan fasting, weight, waist circumference, and inflammatory markers (fibrinogen, hs-CRP) improved, but fructosamine (a short-term glucose marker) rose temporarily, indicating transient worsening of glycemic control.
Intermittent fasting in the treatment of type 2 diabetes
A 2025 review of the literature concludes that intermittent fasting improves glycemic control, insulin sensitivity, and weight in type 2 diabetes, but emphasizes safety monitoring, especially for insulin users, due to hypoglycemia risk.