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Intermittent Fasting for Type 2 Diabetes Remission: What the Evidence Says

A 2023 trial found 47% remission with an intermittent calorie-restricted diet. Dr. Sayantan Banerjee explains 16:8, 5:2 and fasting safely with diabetes medicines.

TYPE 2 DIABETES REMISSION

Dr. Sayantan Banerjee

10/31/20268 min read

Intermittent fasting has gone from a niche idea to one of the most searched diet terms in the world. For people with type 2 diabetes, the question is practical. Can it help bring glucose down, and can it lead to remission? And is it safe when you are taking diabetes medicines?

The short version is that intermittent fasting can work very well for some people with type 2 diabetes, mainly because it helps them eat less and lose weight. It isn't magic, and it can be risky with certain medicines. This article goes through what the trials show, the different types of fasting, and how to try it safely.

What intermittent fasting means

Intermittent fasting is an umbrella term for eating patterns that alternate periods of eating with periods of not eating, or eating very little. The main types are:

Time-restricted eating. You eat all your food within a set window each day, for example 8 or 10 hours, and fast for the rest. The well-known 16:8 pattern means a 16-hour fast and an 8-hour eating window.
The 5:2 diet. You eat normally on five days a week and have around 500 to 800 calories on two non-consecutive days.
Alternate-day fasting. You alternate normal eating days with fasting or very low calorie days.
Intermittent calorie restriction. Periods of very low calorie intake, often several days in a row, separated by longer periods of normal eating.

What these share is that they reduce total food intake without asking you to count every calorie every day. Many people find that easier to stick to.

Why it might help in type 2 diabetes

The main reason is simple. Most people eat less overall when they fast intermittently, and they lose weight. As I explain in my article on how much weight you need to lose, weight loss reduces fat in the liver and pancreas, which is the core of remission.

There may be extra benefits too, though the evidence is less certain. Fasting periods lower insulin levels for longer each day. The body switches to using more fat for fuel. Some studies suggest that eating earlier in the day, when insulin sensitivity tends to be higher, may help glucose control more than eating late at night.

It is important not to overstate these extras. In trials that matched total calories, intermittent fasting usually performed about the same as normal calorie restriction. Its main advantage is that some people find it easier to keep up.

What the trials show

A trial from China, published in the Journal of Clinical Endocrinology & Metabolism in 2023, is the most direct test of intermittent fasting for remission so far. It included 72 people aged 38 to 72 who had had type 2 diabetes for 1 to 11 years, with BMIs between about 19 and 30. Many were taking diabetes medicines, and some were on insulin.

The intervention group followed an intermittent calorie-restricted diet, built on repeated short cycles of very low calorie days followed by normal eating, for three months, under close supervision. Medicines were adjusted and stopped by the team.

After three months of the diet and three months of follow-up, 47% of the intervention group were in remission, against about 3% of the control group. At 12 months, 44% were still in remission. Average weight loss was about 6 kg, which is far less than in DiRECT. Medication costs in the intervention group were about 77% lower.

This is encouraging, especially for people with lower BMIs. But it was a small, single-centre trial, and the diet was supervised carefully. We need larger studies before treating these numbers as typical.

Other trials have looked at glucose control rather than remission. A 12-month Australian trial published in 2018 compared the 5:2 approach with continuous calorie restriction in people with type 2 diabetes. HbA1c fell by a similar amount in both groups, and weight loss was similar. A 2023 US trial from the University of Illinois Chicago found that eight-hour time-restricted eating led to more weight loss over six months than calorie counting in people with type 2 diabetes, with similar improvements in HbA1c.

In people with obesity but without diabetes, a large Chinese trial published in the New England Journal of Medicine in 2022 found that adding time-restricted eating to calorie restriction didn't produce extra weight loss over 12 months. That supports the idea that the main effect of fasting is on how much you eat.

Taken together, the message is consistent. Intermittent fasting works about as well as other calorie-reduction approaches, and it suits some people much better.

The safety issue: your medicines

This is the most important part of this article. Fasting while taking certain diabetes medicines can be dangerous.

Insulin — Examples: All types; Main fasting risk: Low blood sugar (hypoglycaemia); What to do: Doses usually need reducing on fasting days. Only fast with your team's plan.
Sulfonylureas — Examples: Gliclazide, glipizide, glimepiride; Main fasting risk: Low blood sugar; What to do: Often reduced or stopped on fasting days. Ask first.
SGLT2 inhibitors — Examples: Dapagliflozin, empagliflozin, canagliflozin; Main fasting risk: Ketoacidosis, dehydration; What to do: Often paused on very low calorie days. Ask first.
Metformin — Examples: Metformin, metformin SR or XR; Main fasting risk: Low risk of hypos on its own; stomach upset; What to do: Usually continued; timing may change.
GLP-1 medicines — Examples: Semaglutide, dulaglutide, liraglutide, tirzepatide; Main fasting risk: Low risk on their own; nausea, dehydration; What to do: Usually continued. Take care with fluids.
DPP-4 inhibitors — Examples: Sitagliptin, linagliptin; Main fasting risk: Low risk on their own; What to do: Usually continued.
Blood pressure tablets — Examples: Various; Main fasting risk: Dizziness as blood pressure falls; What to do: May need reducing as weight falls.

This table is a general guide only. Your own plan must come from your doctor, pharmacist or diabetes nurse.

Signs of low blood sugar include shaking, sweating, a racing heart, confusion and sudden hunger. If you take insulin or a sulfonylurea, check your glucose more often when you start fasting, and know how to treat a hypo with fast-acting glucose.

Who shouldn't fast without specialist advice

Intermittent fasting is not suitable for everyone. Talk to a specialist first, or avoid it, if you:

are pregnant, breastfeeding or trying to conceive
have a history of eating disorders
have had frequent or severe hypos
have advanced kidney disease
are frail, elderly or underweight
have type 1 diabetes
take several glucose-lowering medicines, including insulin

Choosing a pattern

There is no single best type of fasting. Choose the one that fits your life.

Time-restricted eating suits people who don't mind skipping breakfast or a late snack, and who like the same routine every day. A 10-hour window, for example 9 am to 7 pm, is a good start. Some people later move to 8 hours.

The 5:2 approach suits people who prefer to eat normally most days and can manage two lower-calorie days. Fasting days work best on busy workdays, not weekends.

Alternate-day fasting is harder for most people and has more dropout in trials. It is best kept for those who have tried other patterns and like the structure.

Whichever you choose, food quality still matters. Fasting followed by large portions of refined carbs and sugary drinks won't help much. Build meals around vegetables, protein, whole grains and healthy fats.

What a fasting day can look like

It often helps to see a pattern written out. These examples are for people who have already agreed a plan with their doctor.

A 10-hour time-restricted day, eating between 9 am and 7 pm:

9 am: two eggs with spinach and tomatoes, a slice of wholegrain toast, tea or coffee.
1 pm: a large salad with chicken, chickpeas or salmon, olive oil dressing, and a piece of fruit.
4 pm: plain Greek yogurt or a small handful of nuts if hungry.
6.30 pm: grilled fish or tofu with roasted vegetables and a small portion of brown rice or new potatoes.
7 pm to 9 am: water, herbal tea, black tea or coffee only.
After dinner: a 10 to 15 minute walk.

A 5:2 lower-calorie day, around 600 calories:

Breakfast: skipped, or black coffee or tea.
Lunch: a bowl of vegetable and lentil soup.
Dinner: a palm-sized portion of chicken or fish with a large plate of steamed or roasted non-starchy vegetables.
Through the day: water, sparkling water, tea and coffee without sugar.

On normal days in the 5:2 pattern, eat sensible portions of the same kinds of foods. The aim isn't to make up for the lower day.

Notice what these days have in common. Protein at each meal, lots of vegetables, few refined carbohydrates, and no sugary drinks. The fasting structure helps, but the food choices do much of the work.

If you use a glucose monitor, compare your readings on fasting and normal days. Many people find their morning readings fall over the first few weeks as liver fat comes down. If you see readings below 4 mmol/L (72 mg/dL), or feel shaky or confused, treat the hypo and contact your team before fasting again.

A safe way to start

Talk to your doctor or diabetes nurse. Bring a list of your medicines and ask how they should change on fasting days.
Start gently. Try a 12-hour overnight fast for a week, for example 7 pm to 7 am. Then move to 10 hours of eating and 14 of fasting.
Keep hydrated. Water, tea and black coffee are fine for most people. Fasting can make you dehydrated, especially with SGLT2 inhibitors.
Check your glucose. If you have a meter or monitor, check more often in the first few weeks, especially in the mornings.
Make the first meal count. Break your fast with protein and vegetables, not sugar or refined carbs.
Track your weight and HbA1c. Weigh yourself weekly and recheck HbA1c after three months.
Stop if you feel unwell. Dizziness, frequent hypos or binge eating are signs the pattern isn't right for you.

Fasting for religious reasons

Many people with type 2 diabetes fast during Ramadan or for other religious reasons. These fasts are often longer, and may involve no water during daylight hours, which raises extra risks. Diabetes organisations, including the International Diabetes Federation and Diabetes UK, publish specific guidance for Ramadan fasting. If you plan to fast, see your doctor several weeks beforehand to adjust your medicines.

Common mistakes

Overeating in the eating window. Fasting only works if total intake falls. If you find yourself eating much more in your window, fasting may not suit you.

Skipping protein. Long fasts with low-protein meals can mean more muscle loss. Aim for a good portion of protein at each meal.

Ignoring sleep. Late-night eating windows can cut into sleep, which affects glucose and appetite the next day.

Expecting fasting to work without weight loss. If your weight doesn't change, your glucose is unlikely to change much either.

How my book can help

Strategic intermittent fasting is one of the four strategies in The Type II Diabetes Remission Strategy, alongside everyday nutrition, progressive exercise and daily habits. The book explains how to combine them safely within a 16-week programme, and stresses talking to your doctor first if you take insulin or sulfonylureas. See the book page.

Frequently asked questions

Can intermittent fasting reverse type 2 diabetes? It can lead to remission in some people, mainly through weight loss. In one 2023 trial, 47% of participants reached remission, though it was small and closely supervised.

Is 16:8 fasting safe for diabetics? For many people, yes, but not if you take insulin or a sulfonylurea without a plan from your doctor.

What is the best fasting schedule for type 2 diabetes? The one you can keep up. Time-restricted eating and 5:2 both have trial evidence.

Will fasting raise my morning blood sugar? Some people see higher fasting readings at first, due to the dawn phenomenon. This often settles as weight falls.

Can I drink coffee while fasting? Black coffee and plain tea are usually fine.

Should I fast if I'm on metformin? Usually yes, with your doctor's agreement. Metformin alone rarely causes hypos.