Why the 5:2 diet isn’t for every diabetic: An expert’s warning

According to Dr Rajiv Kovil, Head of Diabetology and weight-loss expert at Zandra Healthcare and co-founder of the Rang De Neela Initiative, intermittent fasting may benefit some people with type 2 diabetes; however, it is not appropriate for everyone and should never be undertaken without medical guidance.

Can intermittent fasting help control blood sugar?

Research suggests that intermittent fasting and time-restricted eating can improve blood sugar control in selected people with type 2 diabetes. Studies have shown improvements in insulin sensitivity, modest reductions in HbA1c levels, weight loss, and lower fasting glucose levels.

“Intermittent fasting can be safe for selected people with type 2 diabetes when done under medical supervision,” Dr Kovil says. “The safety depends on the medications used, baseline glucose control, and how well the person understands glucose monitoring.”

However, fasting can backfire if people continue their usual medication doses during fasting periods. This can lead to hypoglycaemia, rebound hyperglycaemia, dehydration, or wide fluctuations in blood sugar levels. In people with poorly controlled diabetes, fasting may also increase the risk of ketosis or worsen metabolic instability.

In poorly controlled diabetes, fasting may trigger ketosis or worsen glycaemic variability (Image: Freepik)

Why medication adjustments matter

Fasting significantly affects how diabetes medications work in the body. Dr Kovil explains that insulin and drugs that can cause hypoglycemia often require dose reductions or temporary discontinuation during fasting periods.

For intermittent energy restriction, individuals with good glycaemic control may need to discontinue hypoglycaemia-causing drugs on fasting days, whereas those with higher HbA1c levels often require insulin dose reductions rather than complete discontinuation. In time-restricted eating, rapid-acting insulin doses are usually reduced, and other medications are adjusted based on glucose trends.

Without these changes, the risk of dangerous hypoglycaemia increases. “Frequent glucose monitoring, hydration, and structured meal planning are essential when diabetics try fasting,” he notes.

Who should avoid intermittent fasting?

While intermittent fasting may benefit some individuals, it is not suitable for everyone. Dr Kovil cautions that people with type 1 diabetes should avoid fasting due to unpredictable insulin needs and the risk of diabetic ketoacidosis. Pregnant or breastfeeding women with diabetes should also not fast because of increased nutritional demands.

People with hypoglycaemia unawareness, active infections, acute illness, eating disorders, advanced kidney disease, or frailty—especially in older adults—are considered high-risk. In such cases, structured nutrition plans are safer than fasting-based approaches.

So, intermittent fasting is not a one-size-fits-all solution for diabetes. While it can improve blood glucose control and weight in carefully selected patients, it carries significant risks if performed without medical supervision.

“Intermittent fasting is a therapeutic tool, not a universal recommendation,” Dr Kovil says, while concluding, “When individualised and monitored, it can help. When done blindly, it can be harmful.”