This study aimed to investigate the glycemic and insulinemic effects of lunch timing based on a fixed feeding window, and the effects of apple preload on postprandial glucose and insulin responses after nutrient-balanced lunch and the subsequent high-fat dinner in healthy participants. Twenty-six participants completed four randomized, crossover experimental trials: (1) early standardized lunch at 12:00 (12S); (2) apple preload to 12S (12A+S); (3) late standardized lunch at 14:00 (14S); and (4) apple preload to 14S (14A+S); wherein twenty participants’ blood samples were collected for insulin analysis following the lunch trails. In each experimental trial, each participant equipped with a continuous glucose monitor (CGM) was provided with a standardized breakfast and a high-fat dinner to be consumed at 8:00 and 18:00, respectively. The late lunch (14S) resulted in significantly elevated glucose peak, delayed insulin peak time, decreased insulin sensitivity, and increased insulin resistance following the lunch; also decreased glycemic response following the subsequent dinner and larger blood glucose fluctuation over the 24-h period compared with the 12S. The 14A+S significantly reduced the glucose peak, the insulin peak time and the glycemic variability following the lunch, also the 24-h glycemic variability compared with the 14S. The insulin sensitivity was significantly improved in the 12A+S, compared with that of the 12S. In conclusion, the present study found that an extra 2-h inter-meal fasting before and after lunch resulted in elevated glycemic response in both macronutrient-balanced meal and high-fat meal in healthy subjects. The negative impact of a late lunch could be partly reversed by the apple preload, without a trade-off of insulin secretion.

It is well established that cold storage results in increased resistant starch and a reduced glycemic index in carbohydrate food. However, the effects of cold storage on the glycemic response of the second meal of cereals remain unclear. The aim of this study was to compare the postprandial glycemic responses between the paired glutinous and non-glutinous grains, either fresh-cooked or refrigerated, after both the first and second meals. In this randomized crossover trial, eighteen healthy female participants consumed eight test meals, each containing 50 g of carbohydrate, including fresh-cooked non-glutinous and glutinous rice, non-glutinous and glutinous millet, and their refrigerated counterparts (4 °C for 24 h). Postprandial blood glucose and insulin were measured at 240 min and 120 min after breakfast. After a standard lunch, the participants’ blood glucose concentrations were measured within 180 min. The rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) contents of the samples were determined by in vitro enzymatic analysis. Cold-stored non-glutinous rice (CR) and cold-stored non-glutinous millet (CM) had a 24.4% and 29.5% lower incremental area under the curve (iAUC_glu) of glucose within 240 min compared to the control (fresh-cooked rice non-glutinous, FR), respectively (p < 0.05). There were no significant differences between either the cold or hot glutinous grains and FR with respect to postprandial glycemic and insulinemic parameters. After a standard lunch, the fresh-cooked non-glutinous millet (FM) achieved a 39.1% lower iAUC_glu0–180 compared to the FR (p < 0.05). FM had the highest percentage of SDS (64.8%, p < 0.05) among all grain samples. Refrigeration treatment reduced the glycemic excursion only in non-glutinous grains at the first meal, but the FM instead of CM demonstrated a significant second meal effect.

The aim of the study was to explore the impact of both the macronutrient composition and snacking timing on the postprandial glycemic insulinemic responses and food intake. Seventeen healthy female volunteers completed the randomized crossover trials. The volunteers were provided a standard breakfast and lunch at 8:00 and 13:00, respectively, and an ad libitum dinner at 18:00. Provided at either 10:30 (midmorning) or 12:30 (preload), the glycemic effects of the three types of 70 kcal snacks, including chicken breast (mid-C and pre-C), apple (mid-A and pre-A), and macadamia nut (mid-M and pre-M), were compared with the non-snack control (CON), evaluated by continuous glucose monitoring (CGM). The mid-M showed increased insulin resistance after lunch compared with CON, while the pre-M did not. The pre-A stabilized the glycemic response in terms of all variability parameters after lunch, while the mid-A had no significant effect on postprandial glucose control. Both the mid-C and pre-C improved the total area under the glucose curve, all glycemic variability parameters, and the insulin resistance within 2 h after lunch compared with CON. The pre-C attained the lowest energy intake at dinner, while the mid-A and the mid-M resulted in the highest. In conclusion, the chicken breast snack effectively stabilized postprandial glycemic excursion and reduced insulin resistance while the macadamia snack did not, regardless of ingestion time. Only as a preload could the apple snack mitigate the glucose response after the subsequent meal.

Randomised controlled trials involving healthy participants were conducted to investigate the impact of cooking and ingestion patterns on the physiological response and preloading effect of air-dried jujube (AJ). The participants’ postprandial glycaemic and insulinemic responses were tested after ingestion of cooked or uncooked air-dried jujube containing 50 g (as a sole food source) or 15 g (as a preload food prior to a rice meal) of available carbohydrates. Compared with the uncooked AJ, the cooked air-dried jujube (CAJ) induced a 34.5% higher glycaemic peak, 57.1% greater glycaemic variability, and a 159.1% larger negative area under the glycaemic response curve when ingested as the only food in a meal. When eaten as a preload prior to a rice meal, the CAJ reduced the postprandial glycaemic peak by 25.17%. The CAJ preload enhanced insulin production in the 15 min after preloading but did not increase the total amount of postprandial insulin secretion. The result suggests that when taken as preload, the loose matrix of cooked fruits may exhibit glycaemic benefits by eliciting early insulin production and may therefore be conducive to the blood glucose management of a carbohydrate-laden meal.

This study aimed to investigate the effect of the oral processing of vegetables induced by texture modification on acute postprandial glycemic response (GR) and insulin response (IR) when co-ingested and ingested prior to a rice meal. In a randomized crossover trial, 14 healthy female subjects consumed (1) co-ingestion of soft broccoli and rice (SR); (2) co-ingestion of hard broccoli and rice (HR); (3) soft broccoli prior to rice (S+R); (4) hard broccoli prior to rice (H+R); (5) rice (R). Postprandial GR and IR was compared between test meals over a period of 180-min, and the oral processing behaviors were measured for each test food samples. Hard broccoli was observed to have a higher mastication time and chews than soft broccoli. All the broccoli meals resulted in reduced incremental peak glucose (IPG) and an increased incremental area under the insulin curve in 180 min (iAUC_0–180) compared with R. The S+R curbed the IPG by 40% with comparable HOMA-IR AUC_0–180 compared with R, while the H+R elevated the HOMA-IR AUC_0–180 by 62% more than that of R. In conclusion, the soft broccoli intake prior to a rice meal effectively attenuated postprandial GR, without lowering insulin sensitivity as its hard counterpart did.

Objectives: This study aimed to investigate the possible association among texture, oral processing and starch digestive characteristics of hard-cooked (HP) and soft-cooked (SP) potato samples, as well as their acute postprandial glycemic and insulinemic response, when co-ingested with rice in a meal. Methods: HP and SP replaced one-third of rice carbohydrates. Postprandial glycemic and insulinemic responses were measured after test meal ingestion. In vitro experiments evaluated sample physicochemical properties. Results: HP retained more resistant starch (RS) and total phenolics than SP. When co-ingested with rice (HP + R), HP elicited more total chews, higher oral sensory exposure time, slower chewing frequency and longer eating duration. HP + R significantly reduced postprandial glucose iAUC, peak glucose and glycemic excursion. SP + R increased glycemic variability despite reduced iAUCglucose. HP + R also lowered iAUCinsulin, peak insulin and insulin resistance index. The hypoglycemic effect did not extend to the second meal, though composite iAUCglucose over 540 min was reduced. Conclusions: Partially substituting rice with hard-cooked potatoes may help stabilize postprandial glycemic and insulinemic responses, an effect largely attributable to RS retention.