Impairment of glucose tolerance in normal adults following a lowered carbohydrate intake

Carbohydrate Intake and Oral Glucose Tolerance Test Results in the Postpartum Period

CONTEXT

The American Diabetes Association (ADA) recommends a 3-day preparatory diet prior to a diagnostic oral glucose tolerance test (OGTT), a test often recommended in postpartum individuals with a history of gestational diabetes (GDM).

OBJECTIVE

Evaluate the relationship between carbohydrate intake and OGTT glucose in 2 cohorts of postpartum individuals.

METHODS

We performed analyses of postpartum individuals from 2 prospective studies with recent GDM (Balance after Baby Intervention, BABI, n = 177) or risk factors for GDM (Study of Pregnancy Regulation of INsulin and Glucose, SPRING, n = 104) .We measured carbohydrate intake using 24-hour dietary recalls (SPRING) or Food Frequency Questionnaire (BABI) and performed 2-hour 75-g OGTTs. The main outcome measure was 120-minute post-OGTT glucose.

RESULTS

There was no relationship between carbohydrate intake and 120-minute post-OGTT glucose level in either study population (SPRING: β = 0.03, [-5.5, 5.5] mg/dL, P = .99; BABI: β = -3.1, [-9.5, 3.4] mg/dL, P = .35). Adding breastfeeding status to the model did not change results (SPRING β = -0.14, [-5.7, 5.5] mg/dL, P = .95; BABI β = -3.9, [-10.4, 2.7] mg/dL, P = .25). There was, however, an inverse relationship between glycemic index and 120-minute post OGTT glucose (BABI: β = -1.1, [-2.2, -0.03] mg/dL, P = .04).

CONCLUSION

Carbohydrate intake is not associated with post-OGTT glucose levels among postpartum individuals. Dietary preparation prior to the OGTT may not be necessary in this population.

Relationship between carbohydrate intake and oral glucose tolerance test results among pregnant women

AIMS

Evaluate the relationship between self-reported carbohydrate intake and oral glucose tolerance test (OGTT) results in pregnancy.

METHODS

We measured carbohydrate intake using 24-hour dietary recall and performed a 2-hour 75-gram OGTT in 95 pregnant women with risk factors for gestational diabetes (GDM) at a median of 26 weeks' gestation. We tested for associations between carbohydrate intake in the 24 hours preceding the OGTT and 60-minute OGTT glucose, glucose at other timepoints, and glucose area under the curve (AUC) using linear regression, with adjustment for potential confounders.

RESULTS

We observed an inverse linear relationship between carbohydrate intake (median 237 grams [interquartile range: 196, 303]) and 60-minute OGTT glucose. For every 50 gram reduction in carbohydrate intake, there was an 8.9 mg/dl increase in 60-minute OGTT glucose (P < 0.01) in an adjusted model. Lower carbohydrate intake was also associated with higher 30-minute (adjusted β = -6.5 mg/dl, P < 0.01) and 120-minute OGTT glucose (adjusted β = -8.1 mg/dl, P = 0.01) and AUC (adjusted β = -767, P < 0.01).

CONCLUSIONS

Carbohydrate intake in the day preceding an OGTT in pregnancy is associated with post-load glucose values, with lower carbohydrate intake predicting higher glucose levels and higher carbohydrate intake predicting lower glucose levels. Carbohydrate restriction or excess before an OGTT may affect GDM diagnosis.

Comparison of oral glucose tolerance test and ambulatory glycaemic profiles in pregnant women in Uganda with gestational diabetes using the FreeStyle Libre flash glucose monitoring system

BACKGROUND

The diagnosis of hyperglycaemia in sub-Saharan Africa (SSA) is challenging. Blood glucose levels obtained during oral glucose tolerance test (OGTT) may not reflect home glycaemic profiles. We compare OGTT results with home glycaemic profiles obtained using the FreeStyle Libre continuous glucose monitoring device (FSL-CGM).

METHODS

Twenty-eight women (20 with gestational diabetes [GDM], 8 controls) were recruited following OGTT between 24 and 28 weeks of gestation. All women wore the FSL-CGM device for 48-96 h at home in early third trimester, and recorded a meal diary. OGTT was repeated on the final day of FSL-CGM recording. OGTT results were compared with ambulatory glycaemic variables, and repeat OGTT was undertaken whilst wearing FSL-CGM to determine accuracy of the device.

RESULTS

FSL-CGM results were available for 27/28 women with mean data capture 92.8%. There were significant differences in the ambulatory fasting, post-prandial peaks, and mean glucose between controls in whom both primary and secondary OGTT was normal (n = 6) and those with two abnormal OGTTs or "true" GDM (n = 7). There was no difference in ambulatory mean glucose between these controls and the 13 women who had an abnormal primary OGTT and normal repeat OGTT. These participants had significantly lower body mass index (BMI) than the true GDM group (29.0 Vs 36.3 kg/m2, p-value 0.014). Paired OGTT/FSL-CGM readings revealed a Mean Absolute difference (MAD) -0.58 mmol/L and Mean Absolute Relative Difference (MARD) -11.9%. Bland-Altman plot suggests FSL-CGM underestimated blood glucose by approximately 0.78 mmol/L.

CONCLUSION

Diagnosis of GDM on a single OGTT identifies a proportion of women who do not have a significantly higher home glucose levels than controls. This raises questions about factors which may affect the reproducibility of OGTT in this population, including food insecurity and atypical phenotypes of diabetes. More investigation is needed to understand the suitability of the OGTT as a diagnostic test in sub-Saharan Africa.

Retrospective Evaluation of an Online Diabetes Health Coaching Program: A Pilot Study

An estimated one third of American adults have prediabetes; over 30 million have type 2 diabetes mellitus. Health and wellness coaching is an emerging tool for preventing and treating chronic disease. Mastering Diabetes (MD) promotes a low-fat, plant-based, whole-food diet, utilizing online education, day-to-day accountability and support, and video conferencing. This pilot study provides a retrospective view of the effectiveness of MD to treat diabetes. Current and former clients of MD were invited to participate in a survey. On completion of the online consent, subjects were asked a series of questions in a REDCap-based survey: age, gender, enrollment date in MD, changes in weight, HbA1c, medication use, overall health, and current level of adherence to achieved changes. Overall, 253 (8.9%) participants responded to the survey; 80.6% were females, mean age was 56 years. Most of those responding (78.4%, P < .001) reported weight loss; 68.8% (P < .001) reported decreased HbA1c; 52.4% reported decreased medication use; 86.8% reported continued health improvement since having participated in MD; and 83.5% found the online program very helpful. This study demonstrated improvement in HbA1c and weight in participants in an online health and wellness coaching. Study limitations prevent drawing generalizable conclusions; further prospective evaluation is needed.

Very low-carbohydrate versus isocaloric high-carbohydrate diet in dietary obese rats

OBJECTIVE

The effects of a very low-carbohydrate (VLC), high-fat (HF) dietary regimen on metabolic syndrome were compared with those of an isocaloric high-carbohydrate (HC), low-fat (LF) regimen in dietary obese rats.

RESEARCH METHODS AND PROCEDURES

Male Sprague-Dawley rats, made obese by 8 weeks ad libitum consumption of an HF diet, developed features of the metabolic syndrome vs. lean control (C) rats, including greater visceral, subcutaneous, and hepatic fat masses, elevated plasma cholesterol levels, impaired glucose tolerance, and fasting and post-load insulin resistance. Half of the obese rats (VLC) were then fed a popular VLC-HF diet (Weeks 9 and 10 at 5% and Weeks 11 to 14 at 15% carbohydrate), and one-half (HC) were pair-fed an HC-LF diet (Weeks 9 to 14 at 60% carbohydrate).

RESULTS

Energy intakes of pair-fed VLC and HC rats were less than C rats throughout Weeks 9 to 14. Compared with HC rats, VLC rats exhibited impaired insulin and glycemic responses to an intraperitoneal glucose load at Week 10 and lower plasma triacylglycerol levels but retarded loss of hepatic, retroperitoneal, and total body fat at Week 14. VLC, HC, and C rats no longer differed in body weight, plasma cholesterol, glucose tolerance, or fasting insulin resistance at Week 14. Progressive decreases in fasting insulin resistance in obese groups paralleled concomitant reductions in hepatic, retroperitoneal, and total body fat.

DISCUSSION

When energy intake was matched, the VLC-HF diet provided no advantage in weight loss or in improving those components of the metabolic syndrome induced by dietary obesity and may delay loss of hepatic and visceral fat as compared with an HC-LF diet.

Effects of a 4-week 70% high carbohydrate/15% low fat diet on glucose tolerance and on lipid profiles

In order to investigate the effect of high carbohydrate/low fat diet on glucose tolerance and on lipid profiles, we performed a 4-week crossover study. Japanese subjects (30 patients with type 2 diabetes mellitus, 15 subjects with impaired glucose tolerance and 8 subjects with normal glucose tolerance) were allocated either 55% standard carbohydrate/30% fat (sc) or 70% high carbohydrate/15% low fat (hc) diet for four weeks, and evaluated by OGTT and various parameters. Then, the diet was crossed over to another diet, and identical parameters were re-evaluated after four weeks. Area under the glucose concentration-time curve (AUG) or triglyceride did not show significant changes between the two diets. HDL-Cholesterol and body mass index decreased significantly by hc diet. Free fatty acids and homeostasis model assessment insulin resistance index showed a tendency to be decreased by hc diet. AUG hc/sc ratio was inversely correlated with AUG or free fatty acids on standard carbohydrate diet. In conclusion, the present 4-week high carbohydrate/low fat diet may be useful to reduce body weight and insulin resistance. The 4-week high carbohydrate/low fat diet did not affect glucose tolerance as a whole. Although the 4-week high carbohydrate/low fat diet decreased HDL-Chol, it did not increase triglyceride.

The relationship between carbohydrate intake and glucose tolerance in pregnant women

OBJECTIVE

We verified whether a misdiagnosis of gestational diabetes mellitus can result in pregnant women when glucose tolerance has deteriorated after a low-carbohydrate meal, and tried to elucidate the mechanism behind the different outcome of the test.

STUDY DESIGN

Twenty-seven pregnant women were given directions for their evening meal the day before each of two 75-g oral glucose tolerance tests (OGTT). The evening meal was either a low-carbohydrate meal (carbohydrate, 6.7%; Low), or a high-carbohydrate meal (carbohydrate, 85.7%; High).

RESULTS

The OGTT showed that the glucose tolerance was significantly impaired after Low than after High, with a significant increase of fasting plasma non-esterified fatty acids (NEFA) level. Moreover, the insulinogenic index (I-I) after High significantly decreased than that after Low.

CONCLUSIONS

The present data suggests that there is a risk of misdiagnosis of impaired glucose tolerance with only one intake of this extremely low-carbohydrate meal on the evening before testing. The decrease of insulin secretion and the activation of glucose-fatty acid cycle may be considered as the mechanism.

The effect of high carbohydrate diet on glucose tolerance in patients with type 2 diabetes mellitus

The effect of high carbohydrate (hc) diet on glucose tolerance and on lipid profiles in patients with type 2 diabetes mellitus is contradicted. Japanese patients with mild type 2 diabetes mellitus were allocated either 55% standard carbohydrate (sc) or 80% high carbohydrate diets for 1 week, and OGTT and lipid profiles were examined. Then the diet was crossed over for another week, and OGTT and other identical parameters were re-evaluated. High carbohydrate diet improved the area under the glucose concentration-time curve (AUG) in 16/24 patients, and significantly increased and decreased 1,5-anhydroglucitol and homeostasis model assessment insulin resistance (HOMA-R) as a whole, respectively. Fasting plasma glucose (FPG) hc/sc ratio was inversely correlated with HOMA-R on a standard carbohydrate diet. High carbohydrate diet significantly decreased LDL- and HDL-cholesterol, whereas it significantly increased triglyceride. Furthermore, hc/sc ratios of the lipid parameters were inversely correlated with the respective parameters on standard carbohydrate diet. The present study indicates that high carbohydrate diet improved glucose tolerance depending on patients and the improvement in FPG was predicted by HOMA-R on a standard carbohydrate diet. The effect of high carbohydrate diet on glucose tolerance and lipid profiles should be investigated through a long-term study in the future.

Decreased carbohydrate intake is more important than increased fat intake in the glucose intolerance by a low-carbohydrate/high-fat diet

A low-carbohydrate/high-fat evening meal impaired the glucose tolerance of healthy subjects to almost the same extent as the impairment caused by overnight fasting. This suggests that the decreased component (carbohydrate) is more relevant than the increased component (fat) to the impairment of glucose tolerance by a low-carbohydrate/high-fat diet.