Eating all meals within a ten-hour window may improve glucose control and insulin sensitivity in overweight people with type 2 diabetes, a new clinical trial reports. 

Besides improving glucose control and insulin sensitivity, the ten-hour eating window caused weight loss while reducing cardiovascular disease risk factors, including triglycerides, total cholesterol, and low-density lipoprotein (LDL) cholesterol levels. 

The study, “Time-restricted feeding improves blood glucose and insulin sensitivity in overweight patients with type 2 diabetes: a randomised controlled trial,” was published in Nutrition and Metabolism. 

Time-restricted feeding (TRF) is an eating pattern that requires individuals to eat all their meals within a four to twelve-hour eating window daily. It does not require calorie counting or changing the type or quality of food people eat. 

Animal studies show that TRF prevents obesity, lowers inflammation, improves glucose control, and reverse the effects of ageing. While time-restricted feeding studies in humans are few, existing studies in overweight people show that it aids fat loss and lowers blood pressure. 

Type 2 diabetes, often a complication of obesity, is an important global health issue that costs health care systems worldwide $827 billion annually. Although TRF is known to cause weight loss in otherwise healthy but overweight individuals, its effects in people with type 2 diabetes who use glucose-lowering medication are unknown.  

Scientists in China now sought to determine the effects of a ten-hour TRF pattern in overweight people with type 2 diabetes. They specifically wanted to find out if TRF could improve glucose control, insulin sensitivity, markers of cardiovascular diseases (e.g., triglycerides, total cholesterol), reduce medication use and cause weight loss. 

Participants in the study were recruited from diabetes clinics by placing adverts around the Zhu Xianyi Hospital of Tianjin Medical University in China. They were then randomly assigned to a 10-hour TRF or control group for 12 weeks. 

The TRF group ate all their meals between 8 am and 6 pm and drank only black tea or water outside their eating window. The control group maintained their regular eating pattern, which was spread over a 15-hour window. 

Participants had blood tests at the start and end of the study to measure fasting glucose, insulin, HbA1c, triglycerides, total cholesterol, low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol. Their insulin, body weight, and body mass index (BMI) were also measured at the start and end of the study. 

A total of 120 adults were enrolled and evenly randomised to the TRF group and control group. The mean age of the participants was 48 years and 46% were female. The participants had lived with type 2 diabetes for a mean of five years. 

At the start of the study, participants in the TRF ate an average of 1,872 kcal daily, but by week 12, they reduced their energy intake to 1,345 kcal daily. Participants in the control group reduced their energy intake by only 76 kcal daily over the 12 weeks. Participants in the TRF group did not experience any adverse effects such as headaches, thirst or diarrhoea.

Compared with the control group, the TRF group significantly reduced their HbA1c (-0.66% vs. -1.54%), fasting blood glucose (-0.78% vs. -1.47%), body weight (0.83kg vs. -2.98kg), BMI (0.42 kg/m² vs. -1.64 kg/m²⁾ and insulin resistance (-0.12 vs -0.51). 

Similarly, the TRF group significantly improved the markers of cardiovascular diseases compared with the control group; triglycerides (-0.23 mmol/L vs. 0.13 mmol/L), total cholesterol (-0.32 mmol/L vs. -0.15 mmol/L), and LDL-cholesterol levels (-0.42 mmol/L vs -0.21 mmol/L) were significantly lower in the TRF group compared with the controls. However, TRF did not affect HDL-cholesterol levels, which remained similar in both groups. 

Medication use and dosage dropped significantly in the TRF group compared with the control group (-0.66 vs. -0.21). Quality of life, measured with the SF-12 health questionnaire, also significantly improved in the TRF group. 

“Our study showed that 10-h TRF reduced body weight and blood glucose and improved insulin sensitivity in overweight patients with type 2 diabetes. These results occurred without deliberate attempts to increase physical activity and change the quality or quantity of diet,” the researchers wrote. 

“Importantly, we also found significant improvement in CVD risk markers (triglycerides, total cholesterol and LDL cholesterol) without the use of statins or fibrates. Additionally, when all the above indicators were significantly controlled, after the TRF intervention, the dosage of hypoglycaemic (glucose-lowering) drugs in the experimental group of participants was significantly reduced, and their perception of physical functions and daily activities were improved,” they added. 

A limitation of the study was that the participants had a low starting BMI, which may limit the generalisability of the results. 

However, “the good compliance, high level of adherence to TRF, and low dropout rate in our study indicate that the 10-h window for TRF may be feasible for patients with type 2 diabetes to follow,” they concluded. 

Should you practice time-restricted feeding with type 2 diabetes?

Although plenty of evidence for its benefits in animal models exists, the proof of TRF’s benefits in healthy humans is limited (but encouraging). And according to the researchers, this is the first clinical study of TRF in people with type 2 diabetes taking medication, so more evidence is needed especially if you fall into this category.

If you have type 2 diabetes, DO NOT start TRF without getting advice from your doctor. Your doctor may need to adjust your medication and advice if it is the correct strategy for you.  If you’re healthy, seek advice from a registered dietitian/nutritionist. TRF is not suitable for people with eating disorders like anorexia, bulimia or binge-eating disorder.