The effect of prolonged fasting on postprandial glucose, insulin, and free fatty acid responses in type 2 diabetes and overweight healthy participants

Abstract

Background: Omitting breakfast, and hence extending the duration of the overnight fast, has been shown to induce hyperglycaemia after subsequent meals in type 2 diabetes (T2D), possibly due to prolonged elevation of free fatty acids (FFA). However, the duration of this effect is unknown. This study aims to investigate the effect of prolonged fasting over 48 hours, in overweight/obese adults who are either healthy or diagnosed with T2D. Methods: This randomised cross-over study included overweight/obese adults, healthy or diagnosed with T2D, aged 40-60 years. The study was of 6-day duration: two 48-hour treatments (Breakfast versus No Breakfast) separated by two wash-out days. Postprandial venous glucose, insulin, and FFAs concentrations were assessed. Interstitial glucose was recorded over 6 days using continuous glucose monitoring (CGM). Results: 16 participants (n=8 T2D, n=8 overweight/obese) completed the study. No Breakfast did not result in a higher glucose area under the curve (AUC) after the subsequent lunch meal among T2D, but did in overweight/obese healthy individuals (p=0.339, p=0.0033; respectively). This was associated with a prolonged elevation in FFA concentrations and delayed postprandial insulin responses. However, in T2D, No Breakfast resulted in a decreased glucose AUC over 12 hours, compared to Breakfast (p=0.0041). For both cohorts, CGM data showed no difference between Breakfast versus No Breakfast over 48 hours. Conclusion: Breakfast omission increases postprandial hyperglycaemia after the subsequent lunch meal. This is in association with a prolonged elevation of FFAs, which has been found to reduce glucose oxidation and increase insulin resistance. However, these effects were only transient. Omitting breakfast decreased overall postprandial glycaemic response, relative to breakfast consumption, in T2D. Thus, omitting breakfast may have short-term benefits for glycaemic control and facilitate a reduction in HbA1c. Further research is needed to determine the long-term effects of habitual breakfast omission.