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| Name | Class |
|---|---|
| Hass Avocado Board | OTHER |
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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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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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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Low-Carbohydrate Diet first, then Low-Fat Diet (IR) | Active Comparator | Participants who were more insulin resistant based on the median AUC for insulin concentrations measured from OGTT prior to randomization. |
|
| Low-Fat Diet first, then Low-Carbohydrate Diet (IS) | Active Comparator | Participants who were more insulin sensitive based on the median AUC for insulin concentrations measured from OGTT prior to randomization. |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Low-Carbohydrate Diet | Behavioral | 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. |
| Measure | Description | Time Frame |
|---|---|---|
| Change in weight | Weight change was calculated as the 12 month value minus the baseline value | Baseline and 12 months |
| Measure | Description | Time Frame |
|---|---|---|
| Change in Fasting Insulin | Fasting insulin change was calculated as the 12 month value minus the baseline value | Baseline and 12 months |
| Change in insulin AUC | Insulin area under the curve (AUC) change was calculated as the 12 month value minus the baseline value. |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Christopher D Gardner, PhD | Stanford University | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Stanford University School of Medicine | Stanford | California | 94305 | United States |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 26638192 | Background | Gardner CD, Offringa LC, Hartle JC, Kapphahn K, Cherin R. Weight loss on low-fat vs. low-carbohydrate diets by insulin resistance status among overweight adults and adults with obesity: A randomized pilot trial. Obesity (Silver Spring). 2016 Jan;24(1):79-86. doi: 10.1002/oby.21331. Epub 2015 Dec 6. |
| Label | URL |
|---|---|
| Study description and summary of results | View source |
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| ID | Term |
|---|---|
| D009765 | Obesity |
| D007333 | Insulin Resistance |
| D015431 | Weight Loss |
| ID | Term |
|---|---|
| D050177 | Overweight |
| D044343 | Overnutrition |
| D009748 | Nutrition Disorders |
| D009750 | Nutritional and Metabolic Diseases |
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| ID | Term |
|---|---|
| D050528 | Diet, Carbohydrate-Restricted |
| D018752 | Diet, Fat-Restricted |
| ID | Term |
|---|---|
| D004035 | Diet Therapy |
| D044623 | Nutrition Therapy |
| D013812 | Therapeutics |
| D004032 | Diet |
| D009747 |
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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.
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|
| Low-Fat Diet | Behavioral | 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. |
|
| Baseline and 12 months |
| Change in Fasting Glucose | Fasting glucose change was calculated as the 12 month value minus the baseline value. | Baseline and 12 months |
| Change in LDL-Cholesterol | LDL-cholesterol change was calculated as the 12 month value minus the baseline value. | Baseline and 12 months |
| Change in HDL-Cholesterol | HDL-cholesterol change was calculated as the 12 month value minus the baseline value. | Baseline and 12 months |
| Change in Triglycerides | Triglycerides change was calculated as the 12 month value minus the baseline value. | Baseline and 12 months |
| Change in systolic and diastolic blood pressure | Blood pressure change was calculated as the 12 month value minus the baseline value. | Baseline and 12 months |
| Plasma fatty acid composition at baseline | Comparison of the plasma fatty acid composition between insulin sensitive and resistant participants at baseline. | Baseline |
| Correlations between insulin markers and plasma fatty acid composition at baseline. | Baseline |
| Interaction between insulin status and diet on 6-month changes in the plasma fatty acid composition. | 6 months |
| Comparison of plasma fatty acid composition changes in participants on low fat and low carbohydrate diets after 6 months. | Baseline and 6 months |
| Correlations between changes in insulin markers, dietary components, and plasma fatty acid composition after 6 months. | 6 months |
| D001835 |
| Body Weight |
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
| D006946 | Hyperinsulinism |
| D044882 | Glucose Metabolism Disorders |
| D008659 | Metabolic Diseases |
| D001836 | Body Weight Changes |
| Nutritional Physiological Phenomena |
| D000066888 | Diet, Food, and Nutrition |
| D010829 | Physiological Phenomena |