An interventional study of Standard Carb Diet and Low Carb Diet in Diabetes Mellitus, Type 1, sponsored by Vanderbilt University Medical Center. Completed at 1 site in United States. Open to participants aged 18 Years to 60 Years. Per ClinicalTrials.gov, last updated 2025-10-28.
Sponsored by Vanderbilt University Medical Center · Not applicable, Interventional, and Treatment
The investigators will test the hypothesis that reducing insulin doses using a low carbohydrate diet (LCD) will be associated with with improved insulin sensitivity (Aim 1) and blood vessel health (Aim 2).
Insulin resistance (IR) is consistently found in patients with type 1 diabetes (T1DM) and pathophysiologically links T1DM with atherosclerotic disease. IR and nascent atherosclerosis, as characterized by endothelial dysfunction, are present early in T1DM. Although atherosclerosis leads to cardiovascular disease (CVD)-the predominant cause of death in T1DM-the early cardiometabolic processes driving atherosclerosis are not currently well-characterized. My overarching hypothesis is that IR and endothelial dysfunction in T1DM are, in part, iatrogenic, occurring as a function of nonphysiologic insulin delivery.
Previous research shows IR in T1DM is closely related to iatrogenic hyperinsulinemia. Iatrogenic hyperinsulinemia in T1DM results from injecting insulin into subcutaneous tissue rather than delivering insulin more physiologically into the hepatic portal vein. Hyperinsulinemia, per se, is closely linked with IR and independently predicts CVD in diabetic and nondiabetic populations. Thus, peripheral insulin delivery brings about unintended adverse cardiometabolic consequences in T1DM. The investigators propose a practical intervention to diminish iatrogenic hyperinsulinemia and thereby mitigate CVD risk. The investigators hypothesize that a reduction in iatrogenic hyperinsulinemia brought about by a low carbohydrate diet (LCD) will independently correlate with improved insulin sensitivity (Aim 1) and endothelial function (Aim 2).
In this pilot study, the investigators will mechanistically dissect the contribution of iatrogenic hyperinsulinemia to IR and endothelial dysfunction in 8 adults with T1DM using a crossover study of LCD vs. standard carbohydrate diet (SCD) to experimentally modify hyperinsulinemia. The investigators will quantify insulin sensitivity using hyperinsulinemic, euglycemic clamps and measure endothelium-dependent flow mediated vasodilation using high-resolution ultrasound.
3,754 studies on the registry are indexed under Diabetes Mellitus, Type 1; 600 are open to participants now.
This study's enrollment of 14 is below the median of 40 across 2,820 interventional studies indexed under Diabetes Mellitus, Type 1.
Browse Diabetes Mellitus, Type 1 studies →Vanderbilt University Medical Center is the lead sponsor of 833 studies on the registry; 155 are open to participants now.
Of its 125 completed or terminated interventional studies of FDA-regulated products, 92 (74%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
medications
other:
Additional exclusion criteria for T1DM subjects
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
HbA1c
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
NYHA class (heart failure)
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Other: Standard Carb Diet · Other: Low Carb Diet
Other: Standard Carb Diet · Other: Low Carb Diet
Approximately 50% of caloric intake will come from carbohydrate consumption.
Approximately 25% of caloric intake will come from carbohydrate consumption.
Change in Insulin Sensitivity Assessed as Glucose Infusion Rates
Participants completed both a one-week RCD and a one-week SCD, separated by a three-week washout. After each intervention, we measured insulin sensitivity using a hyperinsulinemic-euglycemic clamp.To express GIR in mg of glucose per kg of fat-free mass per minute (mg/kg FFM/min), we divided the dextrose infusion rate by the fat-free mass determined by DEXA. Insulin sensitivity showed no significant difference between diets. GIR was 8.1 mg/kg FFM/min after the RCD and 8.6 mg/kg FFM/min after the SCD.
Time frame: week 1 and week 5
14 patients were screened for eligibility between November 2021 and March 2024. We recruited adults with type 1 diabetes (age 18-60 years, BMI 18-33 kg/m2, HbA1c 5.9-9.0%) from the Vanderbilt Eskind Diabetes Clinic and community sources in Nashville, TN.
| Milestone | Standard Carb Diet then Low Carb Diet | Low Carb Diet then Standard Carb Diet |
|---|---|---|
| Started | 6 | 6 |
| Completed | 6 | 6 |
| Not completed | 0 | 0 |
| Milestone | Standard Carb Diet then Low Carb Diet | Low Carb Diet then Standard Carb Diet |
|---|---|---|
| Started | 6 | 6 |
| Completed | 6 | 6 |
| Not completed | 0 | 0 |
| Milestone | Standard Carb Diet then Low Carb Diet | Low Carb Diet then Standard Carb Diet |
|---|---|---|
| Started | 6 | 6 |
| Completed | 6 | 6 |
| Not completed | 0 | 0 |
Participants completed both a one-week RCD and a one-week SCD, separated by a three-week washout. After each intervention, we measured insulin sensitivity using a hyperinsulinemic-euglycemic clamp.To express GIR in mg of glucose per kg of fat-free mass per minute (mg/kg FFM/min), we divided the dextrose infusion rate by the fat-free mass determined by DEXA. Insulin sensitivity showed no significant difference between diets. GIR was 8.1 mg/kg FFM/min after the RCD and 8.6 mg/kg FFM/min after the SCD.
| mg/kg FFM/min | Standard Carb Diet | Low Carb Diet |
|---|---|---|
| Change in Insulin Sensitivity Assessed as Glucose Infusion Rates | 8.6 (7.0 to 11.0) | 8.1 (6.7 to 10.1) |
Collected over through study completion, an average of 1 year. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Standard Carb Diet | 0/12 (0%) | 0/12 (0%) | 2/12 (16.7%) |
| Low Carb Diet | 0/12 (0%) | 0/12 (0%) | 1/12 (8.3%) |
| Event | Standard Carb Diet | Low Carb Diet |
|---|---|---|
| HeadacheNervous system disorders | 2/12 | 0/12 |
| ShakinessNervous system disorders | 0/12 | 1/12 |
| Age, Continuous(years) | All Study Participants |
|---|---|
| Median | 33.9 (25.0 to 39.0) |
| Sex: Female, Male(Participants) | All Study Participants |
|---|---|
| Female | 7 |
| Male | 5 |
| Race (NIH/OMB)(Participants) | All Study Participants |
|---|---|
| American Indian or Alaska Native | 0 |
| Asian | 0 |
| Native Hawaiian or Other Pacific Islander | 0 |
| Black or African American | 1 |
| White | 11 |
| More than one race | 0 |
| Unknown or Not Reported | 0 |
| Region of Enrollment(participants) | All Study Participants |
|---|---|
| United States | 12 |
| BMI(kg/m^2) | All Study Participants |
|---|---|
| Median | 26.5 (21.7 to 28.4) |
| Weight(kg) | All Study Participants |
|---|---|
| Median | 75.3 (66.8 to 92.0) |
| Height(m) | All Study Participants |
|---|---|
| Median | 1.75 (1.68 to 1.88) |
| Waist-to-hip ratio(ratio) | All Study Participants |
|---|---|
| Median | 0.83 (0.75 to 0.88) |
7 further baseline measures are reported on the registry.
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: Yes — The datasets generated during and/or analyzed during the current study can be available from the corresponding author upon reasonable request. Data sets can be made available beginning 3 months and ending 5 years following article publication. No applicable resources have yet been generated or analyzed during the current study.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Clinical study report
Ran from Nov 2021 to primary completion in Jun 2024, 30 months.
Results were first posted in Oct 2025, 1 year 4 months after primary completion.
Of 844 non-industry interventional studies with no phase under Diabetes Mellitus, Type 1, half reached primary completion within 19 months of starting (the median), counting those still running; a quarter within 10 and three quarters within 38. This study's 30 months is above that.
Counting every sponsor, half of 949 studies reached it within 18 months; a quarter within 9 and three quarters within 35.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Sep 2025. You cannot join it, but the record below documents what was studied.
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