Low-carb breakfast tames glucose spikes in type 2 diabetes

By Susha Cheriyedath, M.Sc.Reviewed by Benedette Cuffari, M.Sc.Jun 6 2023

In a recent study published in The American Journal of Clinical Nutrition, researchers report that a low-carbohydrate (LC) diet led to a 74% reduction in postprandial glucose and lower glycemic variability in type 2 diabetics compared to those fed a standard low-fat breakfast. 

Study: Impact of a Low-Carbohydrate Compared with Low-Fat Breakfast on Blood Glucose Control in Type 2 Diabetes: A Randomized Trial. Image Credit: Patrycja St / Shutterstock.com

Background

Glycemic variability and postprandial increases in blood glucose are independent risk factors for heart disease and mortality in people with type 2 diabetes (T2D). Likewise, daily fluctuations in blood glucose levels, including hyper- and hypoglycemia, can increase the risk of diabetes complications.

Heart disease is a significant cause of morbidity and mortality in T2D patients; therefore, strategies to lower postprandial glucose variations and glycemic variability are crucial. Although a diet low in carbohydrates is considered a potent dietary strategy for better glucose control, poor dietary adherence can limit the benefits of this type of diet.   

The consumption of carbohydrates causes a rapid increase in blood glucose levels in individuals with T2D, especially in the morning. Therefore, one potential and straightforward solution could be to reduce the carbohydrate content of just one meal a day, such as breakfast, in people with diabetes without modifying the macronutrient composition of other meals.

About the study

The present study involved a 12-week, two-site, parallel-arm randomized control trial (RCT) during the coronavirus disease 2019 (COVID-19) pandemic. The objective of this study was to determine whether a breakfast low in carbohydrates can improve glucose control in individuals with T2D as compared to a low-fat breakfast.

The eligibility criteria included T2D diagnosed by a physician, age between 20 and 79 years, current HbA1c of less than 69 mmol/L or 8.5%, blood pressure less than 160/99 mmHg, and a body mass index (BMI) greater than 25 kg/m².

Smokers, individuals using exogenous insulin, those who were on more than two glucose-lowering medications, those receiving treatment for autoimmune or inflammatory diseases, cancer, and liver or kidney disorders, people who were on corticosteroids, hormone replacement therapy (HRT), or anti-inflammatory medications those with allergies or some dietary restrictions, as well as those who were unable to follow the diet prescription were excluded from the trial.

Study procedures were explained to the participants, and digital consent was obtained by the research team members through video conference or telephone due to restrictions imposed by the pandemic. The primary outcome of the study was changes in HbA1c levels.

Data related to self-reported anthropometrics, glucose monitoring, and dietary information of the participants were gathered. The participants also completed the Godin Leisure-Time Exercise Questionnaire to report physical activity.

Study findings

Of the 246 participants who were pre-screened for the study, 127 individuals with T2D satisfied the inclusion criteria. After randomization, 60 individuals were assigned to the LC breakfast group and 61 to the low-fat breakfast group.

The mean age of the participants was 64 years, HbA1c was 7.0, and BMI was 32.3 kg/m², with 53% of the participants being women. While carbohydrate intake was significantly lower in the LC breakfast group, no significant between-group differences were observed in daily fat or protein intake.

After 12 weeks of consuming an LC breakfast, HbA1c decreased by about 0.3%; however, the between-group HbA1c difference was only slightly significant. No significant differences were observed between LC and low-fat groups in terms of BMI, weight, or waist circumference. Additionally, no significant between-group differences in physical activity or hunger and satiety were observed during the study period.

In the LC group, total self-reported daily energy was -242 kcal, and carbohydrate intake was -73 g. Both values were lower as compared to the low-fat group; however, their significance was not clear. Parameters such as glycemic variability, mean and maximum glucose, standard deviation, time above range, and area under the curve were significantly lower as compared to the low-fat group.

Conclusions

There is extensive evidence to suggest that carbohydrate restriction improves glycemic control in individuals with T2D. Although the primary outcome of the current study was not significantly different between the two groups, many other glucose monitoring metrics were better in the LC breakfast group as compared to the low-fat breakfast group during the monitoring periods. Longer and more controlled studies may help lead to significant HbA1c reductions in the LC group as compared to the low-fat group.

The current study also demonstrated high compliance with breakfast interventions, despite being a remote study with minimal supervision. High feasibility of the LC breakfast over the 12-week study period was also observed, thus indicating that moderate carbohydrate restrictions are easier for individuals to comply with as compared to severe carbohydrate restrictions.

Overall, the study findings suggest that consuming an LC breakfast could be a simple and more effective dietary strategy that helps reduce overall carbohydrate and energy intake and improve multiple glucose monitoring variables in individuals with T2D as compared to consuming a low-fat breakfast.