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Weight Loss Diet Study: Low Carb vs Low Fat

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ClinicalTrials.gov Identifier: NCT01661426
Recruitment Status : Completed
First Posted : August 9, 2012
Last Update Posted : August 10, 2020
Sponsor:
Collaborator:
Hass Avocado Board
Information provided by (Responsible Party):
Christopher Gardner, Stanford University

Brief Summary:

The traditional weight loss diet recommended by health professionals has been a low-fat, high-carbohydrate, calorie restricted diet. This recommendation has been challenged by a number of alternative dietary strategies, particularly low-carbohydrate diets. In several recent weight loss studies insulin resistant adults had more success with low- vs. high-carbohydrate diets, in contrast to insulin sensitive adults who had either more success or comparable success with the low-fat diets. The investigators enrolled 61 people with a wide range of insulin sensitivity/resistance. After determining their insulin resistance status, the investigators will split them in the middle and randomly assign them to one of four groups for six months: (1) Low-Carbohydrate/Insulin Resistant (LC/IR); (2) Low-Carbohydrate/Insulin Sensitive (LC/IS); (3) Low-Fat/Insulin Resistant (LF/IR); and (4) Low-Fat/Insulin Sensitive (LF/IS) (15 people/group). After 6 months the participants will switch diet for the following 6 months, i.e. those randomized to the Low-Carbohydrate diet will switch to the Low-Fat diet and vice-versa. The primary outcome of this study is to determine whether weight loss success can be increased if one follows the dietary approach appropriately matched to their insulin resistance status. Secondary outcomes include fasting insulin, glucose, lipids, and fatty acid composition.

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Condition or disease Intervention/treatment Phase
Obesity Insulin Resistance Behavioral: Low-Carbohydrate Diet Behavioral: Low-Fat Diet Not Applicable

Detailed Description:

The investigators hope to learn whether matching the weight loss diet to one's insulin resistance status will increase weight loss the success. The relevance of these findings is highlighted by the fact that the national recommendations for weight loss are to follow a high-carbohydrate, low-fat diet. This would imply that about half the population has been given the wrong advice in regards to the most successful dietary pattern for weight loss.

Plasma fatty acid composition patterns have been shown to be associated with both insulin resistance and/or carbohydrate intake. As secondary analyses, the investigators will explore: (1) differences in plasma fatty acid composition between insulin sensitive and resistant participants at baseline; (2) the correlations between insulin markers and plasma fatty acid composition at baseline; (3) the interaction between insulin status and diet on 6-month changes in the plasma fatty acid composition; (4) plasma fatty acid composition changes in participants on low fat and low carbohydrate diets after 6 months; and (5) the correlations between changes in insulin markers, dietary components, and plasma fatty acid composition after 6 months.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 61 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Intervention Model Description: The study employed a 2 x 2 crossover design: LF vs. LC diets and more IR vs. more IS. Study participants were classified as more IR or more IS based on the median AUC for insulin concentrations measured from an oral glucose tolerance test (OGTT) prior to randomization. Participants above the median were considered more IR and those below the median were considered more IS. A random number generator was used to stratify the randomization to LF vs. LC by insulin resistance status and gender. Participants followed their assigned diet for 6 months and then switched to the opposite diet for another 6 months.
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary Purpose: Prevention
Official Title: Weight Loss Diet Study: Low Carbohydrate vs. Low Fat and Insulin Resistance Status
Study Start Date : April 2012
Actual Primary Completion Date : March 2013
Actual Study Completion Date : March 2013

Resource links provided by the National Library of Medicine


Arm Intervention/treatment
Active Comparator: Low-Carbohydrate Diet first, then Low-Fat Diet (IR)
Participants who were more insulin resistant based on the median AUC for insulin concentrations measured from OGTT prior to randomization.
Behavioral: Low-Carbohydrate Diet
Counseling/instruction on how to follow a healthy low-carbohydrate diet for 6 months. One evening class/week for 8 weeks (8 total classes). Then one class every other week for 8 weeks (4 total classes). Then one class every four weeks for 8 weeks (2 total classes): 14 evening classes, total.

Behavioral: Low-Fat Diet
Counseling/instruction on how to follow a healthy low-fat diet for 6 months. One evening class/week for 8 weeks (8 total classes). Then one class every other week for 8 weeks (4 total classes). Then one class every four weeks for 8 weeks (2 total classes): 14 evening classes, total.

Active Comparator: Low-Fat Diet first, then Low-Carbohydrate Diet (IS)
Participants who were more insulin sensitive based on the median AUC for insulin concentrations measured from OGTT prior to randomization.
Behavioral: Low-Carbohydrate Diet
Counseling/instruction on how to follow a healthy low-carbohydrate diet for 6 months. One evening class/week for 8 weeks (8 total classes). Then one class every other week for 8 weeks (4 total classes). Then one class every four weeks for 8 weeks (2 total classes): 14 evening classes, total.

Behavioral: Low-Fat Diet
Counseling/instruction on how to follow a healthy low-fat diet for 6 months. One evening class/week for 8 weeks (8 total classes). Then one class every other week for 8 weeks (4 total classes). Then one class every four weeks for 8 weeks (2 total classes): 14 evening classes, total.




Primary Outcome Measures :
  1. Change in weight [ Time Frame: Baseline and 12 months ]
    Weight change was calculated as the 12 month value minus the baseline value


Secondary Outcome Measures :
  1. Change in Fasting Insulin [ Time Frame: Baseline and 12 months ]
    Fasting insulin change was calculated as the 12 month value minus the baseline value

  2. Change in insulin AUC [ Time Frame: Baseline and 12 months ]
    Insulin area under the curve (AUC) change was calculated as the 12 month value minus the baseline value.

  3. Change in Fasting Glucose [ Time Frame: Baseline and 12 months ]
    Fasting glucose change was calculated as the 12 month value minus the baseline value.

  4. Change in LDL-Cholesterol [ Time Frame: Baseline and 12 months ]
    LDL-cholesterol change was calculated as the 12 month value minus the baseline value.

  5. Change in HDL-Cholesterol [ Time Frame: Baseline and 12 months ]
    HDL-cholesterol change was calculated as the 12 month value minus the baseline value.

  6. Change in Triglycerides [ Time Frame: Baseline and 12 months ]
    Triglycerides change was calculated as the 12 month value minus the baseline value.

  7. Change in systolic and diastolic blood pressure [ Time Frame: Baseline and 12 months ]
    Blood pressure change was calculated as the 12 month value minus the baseline value.

  8. Plasma fatty acid composition at baseline [ Time Frame: Baseline ]
    Comparison of the plasma fatty acid composition between insulin sensitive and resistant participants at baseline.

  9. Correlations between insulin markers and plasma fatty acid composition at baseline. [ Time Frame: Baseline ]
  10. Interaction between insulin status and diet on 6-month changes in the plasma fatty acid composition. [ Time Frame: 6 months ]
  11. Comparison of plasma fatty acid composition changes in participants on low fat and low carbohydrate diets after 6 months. [ Time Frame: Baseline and 6 months ]
  12. Correlations between changes in insulin markers, dietary components, and plasma fatty acid composition after 6 months. [ Time Frame: 6 months ]


Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Age: > or = 18 years of age
  • Women: Pre-menopausal (self-report) and <50 years of age
  • Men: <50 years of age
  • Race/Ethnicity: All
  • BMI (body mass index): 28-40 kg/m2 (need to lose >10% body weight to achieve healthy BMI)
  • Body weight stable for the last two months, and not actively on a weight loss plan
  • No plans to move from the area over the next 14 months
  • Available and able to participate in the evaluations and intervention for the study period
  • Willing to accept random assignment
  • To enhance study generalizability, people on medications not noted below as specific exclusions can participate if they have been stable on such medications for at least three months
  • Ability and willingness to give written informed consent
  • No known active psychiatric illness

Exclusion Criteria:

  • Pregnant, lactating, within 6 months post-partum, or planning to become pregnant in the next 12 months; no menstruation for the previous 12 months
  • Diabetes (type 1 and 2) or history of gestational diabetes or on hypoglycemic medications for any other indication
  • Prevalent diseases: Malabsorption, renal or liver disease, active neoplasms, recent myocardial infarction, hypertension (except for those stable on hypertensive medications) (<6 months) (patient self-report and, if available, review of labs from primary care provider)
  • Smokers (because of effect on weight and lipids)
  • History of serious arrhythmias, or cerebrovascular disease
  • Uncontrolled hyper- or hypothyroidism (TSH not within normal limits)
  • Medications: Lipid lowering, diabetes medications, and those known to affect weight/energy expenditure
  • Excessive alcohol intake (self-reported, >3 drinks/day)

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT01661426


Locations
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United States, California
Stanford University School of Medicine
Stanford, California, United States, 94305
Sponsors and Collaborators
Stanford University
Hass Avocado Board
Investigators
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Principal Investigator: Christopher D Gardner, PhD Stanford University
Additional Information:
Publications:
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Responsible Party: Christopher Gardner, Associate Professor of Medicine, Stanford University
ClinicalTrials.gov Identifier: NCT01661426    
Other Study ID Numbers: SU-07262012-10669
First Posted: August 9, 2012    Key Record Dates
Last Update Posted: August 10, 2020
Last Verified: August 2020
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: No

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Studies a U.S. FDA-regulated Drug Product: No
Studies a U.S. FDA-regulated Device Product: No
Keywords provided by Christopher Gardner, Stanford University:
Adults
Weight loss
Diet
Insulin Resistance
Fatty acid composition
Additional relevant MeSH terms:
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Insulin Resistance
Weight Loss
Body Weight Changes
Body Weight
Hyperinsulinism
Glucose Metabolism Disorders
Metabolic Diseases