by the Scientific Team of Fondazione Valter Longo
Type 2 diabetes is an increasingly common chronic condition, characterized by high levels of sugar in the blood (blood glucose). It stems from impaired insulin action. Insulin is the hormone produced by the pancreas that regulates glucose levels. The condition is often associated with overweight or obesity and, if not properly managed, can increase the risk of cardiovascular and metabolic complications. For this reason, intervening on lifestyle and diet is essential to improve metabolic control and prevent complications.
This context frames a recent randomized clinical trial (in which participants were randomly assigned to different groups, making the results more reliable) that compared two nutritional strategies: traditional calorie restriction, and the same diet combined with time-restricted eating.
The study involved 99 adults with type 2 diabetes and obesity, between the ages of 21 and 60, and followed them for 12 weeks. Participants were divided into two groups: one followed a calorie-restricted diet, meaning a reduction in daily calories compared to their needs; the other followed the same diet, but with a 12-hour overnight fast (for example, from 8:00 p.m. to 8:00 a.m. the next morning). Both groups received a personalized meal plan and were regularly monitored by experienced nutritionists.
In addition, both groups had similar levels of physical activity, making the comparison between the two strategies more reliable.
Both groups showed improvements, but with interesting differences. Those who also followed the 12-hour overnight fast achieved more pronounced benefits. In particular, the study observed: greater weight loss; better blood glucose control, with a more marked reduction in HbA1c (a blood test that reflects average blood glucose over the previous 2–3 months); a greater reduction in body fat; and a more significant decrease in waist circumference, which is an indicator of cardiovascular risk.
In terms of safety, both dietary protocols were well tolerated by participants. There were no episodes of hypoglycemia (an excessive drop in blood sugar), and only a few participants reported mild symptoms, such as headache.
Overall, these data suggest that incorporating a 12-hour overnight fast into a controlled nutritional program may help improve blood glucose control and support weight loss in people with type 2 diabetes.
It is also a relatively simple approach to follow, one that can easily fit into daily life and could potentially improve adherence to the meal plan.
It is important to stress that this type of intervention must always be personalized and carried out under the supervision of qualified professionals, especially in the presence of conditions such as diabetes. Furthermore, longer studies will be needed to confirm these results over time and assess their long-term effects.
M Abdel Fattah S, M Abbassi M, Abd Elshafy S, A Hegazy M, F Farid S. The impact of intermittent fasting during weight reduction in people living with type 2 diabetes mellitus: a randomized clinical trial. Eur J Clin Nutr. 2026 Mar;80(3):299-306. doi: 10.1038/s41430-025-01693-z. Epub 2026 Jan 7. PMID: 41501473; PMCID: PMC13008765.