The rising prevalence of obesity and diabetes has made pre-diabetic adults who spend much of their day in a state of postprandial hyperglycaemia a target demographic for preventive lifestyle interventions against type 2 diabetes and related cardiovascular conditions.
Researchers at the Australian Catholic University and Baker Heart and Diabetes Institute conducted a study whereby they compared the effect of high-energy versus low-energy first meals on glucose and insulin responses during prolonged sitting in pre-diabetic individuals.
Which way to go — high or low?
They recruited 13 overweight and obese pre-diabetic adults aged 60 to 66, with a BMI of between 33kg/m2 and 37kg/m2, to complete two randomised trials, both of which entailed 10 hours of uninterrupted sitting.
One involved incorporating three meals with matching macronutrient compositions but different energy distributions: a high-energy breakfast (50% of the daily energy intake), followed by lunch (30%) and dinner (20%).
The other involved a low-energy breakfast (20%), followed by lunch (30%) and dinner (50%).
The researchers then took venous blood samples between 8 AM and 6 PM to determine the participants' plasma glucose and insulin concentrations, alongside 24-hour continuous glucose monitoring (CGM).
They then reported that total glucose and mean plasma glucose concentrations were greater after the high-energy breakfast, compared to the low-energy breakfast.
Those who had consumed the high-energy breakfast were also found to have higher plasma glucose levels after breakfast, but lower levels after lunch.
In addition, total insulin was greater following the high-energy breakfast than after the low-energy breakfast. At the same time, 24-hour CGM found no differences in mean and total glucose between conditions.
The researchers wrote: "Compared to a low-energy first meal, a high-energy first meal elicited exaggerated plasma insulin and glucose responses until lunch, but had little effect on 24-hour glycaemia.
"During periods of prolonged sitting, adults with pre-diabetes may have more beneficial postprandial insulin responses to a low-energy first meal."
Issues of size and timing
One of the study's limitations was that its sample size was smaller than initially planned, and there was a lack of venous sampling after 6 PM, leading to the inability to characterise the postprandial insulin, C-peptide or GLP-1 responses after dinner.
The timing of the meals was also similar to a time-restricted feeding protocol that could have compounded the postprandial hyperglycaemic response to lunch and dinner.
The researchers concluded: "Our results support a role for first-meal energy intake to influence postprandial glucose and insulin responses in adults with pre-diabetes, independent of macronutrient composition.
"In contrast to the results of studies of meal energy distribution, the clinical advantage of a high-energy first meal to improve daily blood glucose regulation was not evident in this investigation in individuals with pre-diabetes.
"For adults with pre-diabetes who experience prolonged sedentary periods, particularly in the hours leading to lunch, a low-energy first meal may be desirable for postprandial glucose and insulin regulation, although 24-hour glycaemic control was not impaired or improved by a high-energy first meal of the same composition.
“These considerations highlight the need for a larger, longer-term intervention, where meal size is the modifiable factor and each meal composition is controlled.
"However, food availability / choices at mealtimes often dictate the composition, so there is also a need to investigate meal size with the consideration of typical meal compositions (i.e., higher carbohydrate intakes at breakfast and higher protein at dinner)."
Source: Nutrients
https://doi.org/10.3390/nu10060733
"Impact of First Meal Size during Prolonged Sitting on Postprandial Glycaemia in Individuals with Prediabetes: A Randomised, Crossover Study"
Authors: Evelyn B. Parr, et al.