Table 2 Experimental study of GCK-related hyperglycemia

Klupa et al.¹⁴

An observational cross-over study of 2 days of high, followed by 2 days of low-carbohydrate intake with a 1-day washout period

10 adults (4 females) with GCK-related hyperglycemia

Mean age 37.4 (range 19–54) years

(diabetes, N = 7), 30.0 (19–52) years

(prediabetes, N = 3)

Mean baseline HbA1c 7.3 (6.1–8.4)%

(diabetes), 6.0 (5.9–6.1)% (prediabetes)

-Mean blood glucose level (MBG)

-Percentage of time above target postprandial blood glucose level defined as 7.8 mmol/L

When the 3 patients with prediabetes were excluded, the remaining 7 patients had higher MBG during exposure to the high-carbohydrate diet than while on the

low-carbohydrate diet (difference of 0.76 mmol/L, P = 0.02)

They also had spent less time above the target postprandial blood glucose level (difference of 11.7%, P = 0.02)

-Lacked a control or comparison group

-Did not control for carryover effects

● Short washout period

● Did not control for potential order effects

● All participants began with high- carbohydrate diet

-Diet and daily caloric intake were not standardized

-In analysis, groups were divided into diabetes and prediabetes-based on FBG. This resulted in overlap of HbA1c between groups and individuals with HbA1c values that are defined as prediabetes analyzed in the diabetes group. With study design limitations, short duration, and separate analysis of prediabetes from diabetes, which was not a predefined exclusion, no recommendation can be made on dietary treatment for GCK-related hyperglycemia.