Complex Effects of Dietary Manipulation on Metabolic Function, Inflammation and Health

Study Overview
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Brief Summary
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The purpose of this research study is to 1) understand how some, but not all people with obesity develop obesity related conditions such as type 2 diabetes and cardiovascular disease, and 2) compare the effects of 3 popular weight loss diets (Mediterranean, low-carbohydrate, or a very-low-fat plant-based diet) in people with obesity.

Detailed Description
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Obesity is associated with a constellation of cardiometabolic abnormalities (including insulin resistance, elevated blood pressure and dyslipidemia) that are risk factors for diabetes and cardiovascular disease. However, not all people experience the typical complications associated with obesity. Approximately 25% of obese people are protected from the adverse metabolic effects of excess fat accumulation and are considered metabolically-normal, based on their normal response to insulin. The mechanisms responsible for the development of insulin resistance and cardiometabolic complications in some, but not all, obese persons are unknown. In people that do develop the typical complications associated with obesity weight loss has profound therapeutic effects. Currently, there are three distinctly different types of diets that have demonstrated considerable benefits in improving cardiometabolic health in both lean and obese people: 1) a Mediterranean diet, 2) a low-carbohydrate, ketogenic diet, and 3) a plant-based, very-low-fat diet. However, there is considerable inter-individual variability in body weight loss among people in response to any given diet, and it is not known why some people lose more weight with one diet than another. The mechanisms responsible for the different weight and metabolic responses to specific types of diets and the independent effects of weight loss and dietary macronutrient composition on cardiometabolic health are unclear. The overarching goal of this project is therefore to fill these gaps in knowledge by conducting a careful cross-sectional characterization of metabolically normal lean, metabolically normal obese and metabolically abnormal obese individuals to compare body composition, body fat distribution, the plasma metabolome, systemic and adipose tissue inflammation and immune system function, adipose tissue and muscle biological function, the gut microbiome, the brain's structure, cognitive function and central reward mechanisms, and taste sensation between groups. . Metabolically abnormal obese participants will then be randomized to follow a Mediterranean, a low-carbohydrate ketogenic or a plant-based, very-low-fat diet to examine the different effects of these diets on the above outcomes with the purpose to determine the beneficial or potentially harmful effects of these different diets.

Official Title
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Complex Effects of Dietary Manipulation on Metabolic Function, Inflammation and Health

Conditions
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Obesity, Insulin Resistance

Intervention / Treatment
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* Other: Metabolically abnormal obese - Mediterranean diet
* Other: Metabolically abnormal obese - Low carbohydrate ketogenic diet
* Other: Metabolically abnormal obese - Plant-based, very-low-fat diet


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Metabolically normal lean subjects must have a BMI ≥18.5 and ≤24.9 kg/m2; Obese subjects must have a BMI ≥30.0 and ≤50.0 kg/m2 Metabolically normal lean and obese subjects must have intrahepatic triglyceride (IHTG) content ≤5%; plasma triglyceride (TG) concentration <150 mg/dl; fasting plasma glucose concentration <100 mg/dl, 2-hr oral glucose tolerance plasma glucose concentration <140 mg/dl, and hemoglobin A1C ≤5.6% Metabolically abnormal obese subjects must have intrahepatic triglyceride (IHTG) content ≥5.6%; HbA1C ≥5.7%, or fasting plasma glucose concentration ≥100 mg/dl, or 2-hr oral glucose tolerance test (OGTT) plasma glucose concentration ≥140 mg/dl. Exclusion Criteria: Medical, surgical, or biological menopause Previous bariatric surgery where the gastrointestinal tract is reconstructed such as Roux-en-Y, sleeve gastrectomy and biliopancreatic diversion surgeries Laparoscopic adjustable gastric band (lab band) surgery within the last 3 years Structured exercise ≥250 min per week (e.g., brisk walking) Unstable weight (>4% change during the last 2 months before entering the study) Significant organ system dysfunction (e.g., diabetes requiring medications, severe pulmonary, kidney or cardiovascular disease) Polycystic ovary syndrome Cancer or cancer that has been in remission for <5 years Major psychiatric illness Conditions that render subject unable to complete all testing procedures (e.g., severe ambulatory impairments, limb amputations, or metal implants that interfere with imaging procedures; coagulation disorders) Use of medications that are known to affect the study outcome measures (e.g., steroids, non-statin lipid-lowering medications) or increase the risk of study procedures (e.g., anticoagulants) and that cannot be temporarily discontinued for this study Use of antibiotics in last 60 days Smoke cigarettes > 10 cigarettes/week Use marijuana >2 x/week, or use of illegal drugs Men who consume >21 units (e.g. glass of wine or bottle of beer) of alcohol per week and women who consume >14 units of alcohol per week Pregnant or lactating women Vegans, vegetarians, those with lactose intolerance and/or severe aversions/sensitivities to eggs, fish, nuts, wheat and soy, and/or any individuals with food allergies that induce an anaphylactic response Persons who are not able to grant voluntary informed consent Persons who are unable or unwilling to follow the study protocol or who, for any reason, the research team considers not an appropriate candidate for this study, including non-compliance with screening appointments or study visits

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Metabolically normal lean - Baseline testing only<br>Metabolically normal lean - Lean individuals that have good glucose (sugar) control, normal plasma triglyceride (fat) levels and a low liver fat content. Dietary intervention - None. | |
| No Intervention: Metabolically normal obese - Baseline testing only<br>Metabolically normal obese - Persons with obesity that have good glucose (sugar) control, normal plasma triglyceride (fat) levels and a low liver fat content. Dietary intervention - None. | |
| Experimental: Metabolically abnormal obese - Mediterranean diet<br>Metabolically abnormal obese - Persons with obesity with glucose levels higher than recommended and a moderate to high amount of fat in the liver. Dietary intervention - A nutritionally balanced diet that includes fruits, vegetables, fish, beans, whole grains, and olive oil with approximately 50% of daily calories coming from complex carbohydrates, 30% of calories from fat, and 20% of calories from protein. | Other: Metabolically abnormal obese - Mediterranean diet<br>* The effect of consuming a Mediterranean diet will be examined over 3 different phases: (i) weight maintenance for 4 to 8 weeks, with all meals provided; (ii) controlled 7-10% weight loss with caloric intake reduced by 25% to achieve the desired amount of weight loss in about 4 to 5 months with all meals provided; and (iii) Independent weight loss for about 4 months. During the independent weight loss phase of the study subjects will be asked to continue to consume a Mediterranean diet but will prepare all their food at home. No food will be provided during this portion of the study.<br>|
| Experimental: Metabolically abnormal obese - Low carbohydrate ketogenic diet<br>Metabolically abnormal obese - Persons with obesity with glucose levels higher than recommended and a moderate to high amount of fat in the liver. Dietary intervention - A very-low-carbohydrate, adequate protein, high-fat diet containing 20 grams of carbohydrate or less per day (about 5% of calories), derived mainly from vegetables. | Other: Metabolically abnormal obese - Low carbohydrate ketogenic diet<br>* The effect of consuming a low-carbohydrate, ketogenic diet will be examined over 3 different phases: (i) weight maintenance for 4 to 8 weeks, with all meals provided; (ii) controlled 7-10% weight loss with caloric intake reduced by 25% to achieve the desired amount of weight loss in about 4 to 5 months with all meals provided; and (iii) Independent weight loss for about 4 months. During the independent weight loss phase of the study subjects will be asked to continue to consume a low carbohydrate ketogenic diet but will prepare all their food at home. No food will be provided during this portion of the study.<br>|
| Experimental: Metabolically abnormal obese - Plant-based very-low-fat diet<br>Metabolically abnormal obese - Persons with obesity with glucose levels higher than recommended and a moderate to high amount of fat in the liver. Dietary intervention - A plant-based diet high in complex carbohydrates and low in fat, protein, and sodium, with approximately 70% of daily calories from carbohydrates, 15% from fat, and 15% from protein. | Other: Metabolically abnormal obese - Plant-based, very-low-fat diet<br>* The effect of consuming a plant-based, very-low-fat diet will be examined over 3 different phases: (i) weight maintenance for 4 to 8 weeks, with all meals provided; (ii) controlled 7-10% weight loss with caloric intake reduced by 25% to achieve the desired amount of weight loss in about 4 to 5 months with all meals provided; and (iii) Independent weight loss for about 4 months. During the independent weight loss phase of the study subjects will be asked to continue to consume a plant-based, very-low-fat diet but will prepare all their food at home. No food will be provided during this portion of the study.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Insulin sensitivity | Whole-body insulin sensitivity will be assessed by using the hyperinsulinemic-euglycemic clamp procedure | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in insulin sensitivity | Whole-body insulin sensitivity will be assessed by using the hyperinsulinemic-euglycemic clamp procedure | Before and after 4 to 8-weeks of weight maintenance and after 7-10% weight loss ( 6-7 months) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 24-hour glucose concentrations | Glucose concentrations will be evaluated from frequent blood samples over a 24 h period | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in 24-hour glucose concentrations | Glucose concentrations will be evaluated from frequent blood samples over a 24 h period | Before and after 4 to 8-weeks of weight maintenance and after 7-10% weight loss ( 6-7 months) | 
| 24-hour hormone concentrations | Plasma hormone concentrations will be evaluated from frequent blood sampling over a 24 h period | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in 24-hour hormone concentrations | Plasma hormone concentrations will be evaluated from frequent blood sampling over a 24 h period | Before and after 4 to 8-weeks of weight maintenance and after 7-10% weight loss ( 6-7 months) | 
| 24-hour cytokine concentrations | Plasma cytokine concentrations will be evaluated from frequent blood sampling over a 24 h period | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| β-cell function | β-cell function will be assessed from a modified oral glucose tolerance test | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in β-cell function | β-cell function will be assessed from a modified oral glucose tolerance test | Before and after 7-10% weight loss ( 6-7 months) and independent weight loss (12 months) in metabolically abnormal obese individuals only. | 
| Insulin clearance | Insulin clearance will be assessed from a modified oral glucose tolerance test and hyperinsulinemic-euglycemic clamp procedure | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Insulin clearance | Insulin clearance will be assessed from a modified oral glucose tolerance test and hyperinsulinemic-euglycemic clamp procedure | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only. | 
| Fat mass and fat free mass | Fat mass and fat free mass will be assessed using dual-energy x-ray absorptiometry (DXA) | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in fat mass and fat free mass | Fat mass and fat free mass will be assessed using dual-energy x-ray absorptiometry (DXA) | Before and after 4 to 8-weeks of weight maintenance, after 7-10% weight loss ( 6-7 months) and after independent weight loss (12 months) | 
| Exosome-mediated intercellular signaling | Signaling between cells and organs will be examined by isolating exosomes (small extracellular vesicles) from blood and adipose tissue | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in exosome-mediated intercellular signaling | Signaling between cells and organs will be examined by isolating exosomes (small extracellular vesicles) from blood and adipose tissue | Before and after 4 to 8-weeks of weight maintenance, after 7-10% weight loss ( 6-7 months) and after independent weight loss (12 months) | 
| Abdominal adipose tissue volumes | Abdominal subcutaneous and intra-abdominal adipose tissue volumes will be assessed by magnetic resonance imagining (MRI) | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in abdominal adipose tissue volumes | Abdominal subcutaneous and intra-abdominal adipose tissue volumes will be assessed by magnetic resonance imagining (MRI) | Before and after 4 to 8-weeks of weight maintenance, after 7-10% weight loss ( 6-7 months) and after independent weight loss (12 months) | 
| Leg adipose tissue volumes | Thigh and calf adipose tissue volumes will be assessed by magnetic resonance imagining (MRI) | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in leg adipose tissue volumes | Thigh and calf adipose tissue volumes will be assessed by magnetic resonance imagining (MRI) | Before and after 4 to 8-weeks of weight maintenance, after 7-10% weight loss ( 6-7 months) and after independent weight loss (12 months) | 
| Intra-hepatic triglyceride content | Intra-hepatic triglyceride content will be assessed by magnetic resonance techniques | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in intra-hepatic triglyceride content | Intra-hepatic triglyceride content will be assessed by magnetic resonance techniques | Before and after 4 to 8-weeks of weight maintenance, after 7-10% weight loss ( 6-7 months) and after independent weight loss (12 months) | 
| Gut microbiome | Gut microbiota, meta-transcriptome (bacterial RNA sequencing to determine what proteins can be made by the microbiota) and the meta-metabolome (metabolites made by the microbiota) will be assessed | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in gut microbiome | Gut microbiota, meta-transcriptome (bacterial RNA sequencing to determine what proteins can be made by the microbiota) and the meta-metabolome (metabolites made by the microbiota) will be assessed | Before and during 4 to 8-weeks of weight maintenance, 7-10% weight loss ( 6-7 months) and independent weight loss (12 months) | 
| Plasma lipid profile | Fasting plasma lipid profile will be assessed by nuclear magnetic resonance (NMR) techniques | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in plasma lipid profile | Fasting plasma lipid profile will be assessed by nuclear magnetic resonance (NMR) techniques | Before and after 4 to 8-weeks of weight maintenance, after 7-10% weight loss ( 6-7 months) and after independent weight loss (12 months) | 
| Aerobic fitness | Maximal oxygen consumption will be assessed using indirect calorimetry during a graded exercise test to volitional fatigue | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in aerobic fitness | Maximal oxygen consumption will be assessed using indirect calorimetry during a graded exercise test to volitional fatigue | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals randomized to the plant-based very-low-fat diet only | 
| Carotid artery intima media thickness | Carotid artery intima media thickness will be assessed by ultrasound imaging | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in carotid artery intima media thickness | Carotid artery intima media thickness will be assessed by ultrasound imaging | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Cardiac structure and function | Ultrasound techniques will be used to assess cardiac structure and function | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in cardiac structure and function | Ultrasound techniques will be used to assess cardiac structure and function | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Endothelial function | Endothelial function will be assessed using a non-invasive device (EndoPat 2000) in response to reactive hyperemia. | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in endothelial function | Endothelial function will be assessed using a non-invasive device (EndoPat 2000) in response to reactive hyperemia. | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Arterial stiffness | Arterial stiffness will be assessed using a non-invasive device (SphygmoCor) | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in arterial stiffness | Arterial stiffness will be assessed using a non-invasive device (SphygmoCor) | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Physical activity | Physical activity will be assessed using tri-axial accelerometry | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in physical activity | Physical activity will be assessed using tri-axial accelerometry | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Sleep efficiency | Sleep efficiency will be assessed using tri-axial accelerometry | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in sleep efficiency | Sleep efficiency will be assessed using tri-axial accelerometry | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Rate of incorporation of 2H2O into lipids | Metabolic pathways relating to lipid (fat) synthesis in the liver and adipose tissue (fat) will be assessed by heavy water (2H2O) ingestion followed by fat biopsies and blood sampling | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in the rate of incorporation of 2H2O into lipids | Metabolic pathways relating to lipid (fat) synthesis in the liver and adipose tissue (fat) will be assessed by heavy water (2H2O) ingestion followed by fat biopsies and blood sampling | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Rate of incorporation of 2H2O into proteins | Metabolic pathways relating to protein synthesis in the muscle and adipose tissue will be assessed by heavy water (2H2O) ingestion followed by skeletal muscle and and adipose tissue biopsies and blood sampling | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in the rate of incorporation of 2H2O into proteins | Metabolic pathways relating to protein synthesis in the muscle and adipose tissue will be assessed by heavy water (2H2O) ingestion followed by skeletal muscle and and adipose tissue biopsies and blood sampling | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Taste intensity | Subjects will be evaluated by using the NIH toolbox Taste Intensity Test | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in taste intensity | Subjects will be evaluated by using the NIH toolbox Taste Intensity Test | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Sweet taste palatability | Sweet palatability will be assessed using the general Labeled Magnitude Scale | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in sweet taste palatability | Sweet palatability will be assessed using the general Labeled Magnitude Scale | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Immune function | Immune cell populations within plasma and adipose tissue will be profiled using multi-color fluorescence activated cell sorting (FACS) techniques. | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in immune function | Immune cell populations within plasma and adipose tissue will be profiled using multi-color fluorescence activated cell sorting (FACS) techniques. | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Food consumption-induced changes in brain blood flow | Food consumption-induced changes in brain blood flow will be assessed by blood-oxygen dependent (BOLD) and arterial spin labeling using functional magnetic resonance imaging (fMRI) techniques | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in food consumption-induced changes in brain blood flow | Food consumption-induced changes in brain blood flow will be assessed by blood-oxygen dependent (BOLD) and arterial spin labeling using functional magnetic resonance imaging (fMRI) techniques | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Transcriptome in blood, muscle and adipose tissue | The transcriptome (all RNA that are responsible for making proteins from DNA templates) will be evaluated by using RNA sequencing techniques | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in transcriptome in blood, muscle and adipose tissue | The transcriptome (all RNA that are responsible for making proteins from DNA templates) will be evaluated by using RNA sequencing techniques | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Epigenome in blood, muscle and adipose tissue | The epigenome (chemical modifications of DNA that signal genes to be on or off) will be evaluated by using Illumina Infinium HumanMethylation450 BeadChip assays. | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). | 
| Change in epigenome in blood, muscle and adipose tissue | The epigenome (chemical modifications of DNA that signal genes to be on or off) will be evaluated by using Illumina Infinium HumanMethylation450 BeadChip assays. | Before and after 7-10% weight loss ( 6-7 months) in metabolically abnormal obese individuals only | 
| Dopamine receptor binding potential | Dopamine receptor binding potential will be assessed by Positron Emission Tomography (PET) using [11C]raclopride in the fasted and fed states | Baseline in fasted and fed states in metabolically abnormal obese participants only. | 
| Subcutaneous abdominal adipose tissue oxygen tension | Oxygen tension will be assessed in subcutaneous abdominal adipose tissue in the abdomen using oxygen-sensitive fiber-optic probes (OxyLiteTM, Oxford Optronix, Ltd) | Baseline only (cross-sectional comparison of metabolically normal lean, metabolically normal obese and metabolically abnormal obese subjects). |