Weight Loss Diet Study: Low Carb vs Low Fat

Weight Loss Diet Study: Low Carbohydrate vs. Low Fat and Insulin Resistance Status

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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Study Overview

• Status: Completed
• Conditions: Obesity; Insulin Resistance
• Intervention / Treatment: Behavioral: Low-Carbohydrate Diet; Behavioral: Low-Fat Diet

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.

• Study Type: Interventional
• Enrollment (Actual): 61
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • California
    • Stanford, California, United States, 94305
      • Stanford University School of Medicine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 50 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

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)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in weight	Weight change was calculated as the 12 month value minus the baseline value	Baseline and 12 months

Secondary Outcome Measures

Outcome Measure	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.	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

Collaborators and Investigators

• Sponsor: Stanford University
• Collaborators: Hass Avocado Board
• Investigators: Principal Investigator: Christopher D Gardner, PhD, Stanford University

Publications and helpful links

General Publications

• 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.

Helpful Links

• Study description and summary of results

Study record dates

Study Major Dates

• Study Start: April 1, 2012
• Primary Completion (Actual): March 1, 2013
• Study Completion (Actual): March 1, 2013

Study Registration Dates

• First Submitted: August 7, 2012
• First Submitted That Met QC Criteria: August 7, 2012
• First Posted (Estimate): August 9, 2012

Study Record Updates

• Last Update Posted (Estimate): February 22, 2023
• Last Update Submitted That Met QC Criteria: February 18, 2023
• Last Verified: February 1, 2023

More Information

Terms related to this study

• Keywords: Insulin Resistance; Adults; Weight loss; Diet; Fatty acid composition
• Additional Relevant MeSH Terms: Glucose Metabolism Disorders; Metabolic Diseases; Body Weight; Hyperinsulinism; Body Weight Changes; Weight Loss; Insulin Resistance
• Other Study ID Numbers: SU-07262012-10669

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No