Tirzepatide Impact Assessment Study

Overview

This study examines how two different weight-loss strategies affect heart and metabolic health, as well as changes at the molecular level in the body. One group includes adults who are starting a GLP-1 receptor agonist medication (i.e., semaglutide or tirzepatide) prescribed by their own doctor for weight loss. The other group includes adults who will participate in a structured lifestyle program combining a reduced-calorie diet with increased physical activity. Both groups complete assessments at the start of the study and again after three months. At each visit, participants have their weight, body composition, blood pressure, and resting metabolic rate measured. A blood draw is collected to evaluate cholesterol, blood sugar, insulin, appetite hormones, and liver and kidney function markers, and to analyze gene activity (RNA sequencing) and metabolites, which are small molecules that reflect how the body is using energy and nutrients. Participants also complete online questionnaires about diet, disordered eating, stress, mental health, and quality of life. Those in the lifestyle group attend three individual nutrition and physical activity counseling sessions over the course of the study. The main goals of the study are (1) to determine whether GLP-1 receptor agonist medication or lifestyle changes produce greater improvements in heart and metabolic health markers over three months; (2) to examine if GLP-1 receptor agonist medication or lifestyle changes produce greater improvement in disordered eating, stress, mental health, and quality of life; (3) to investigate if GLP-1 receptor agonist medication or lifestyle changes produce greater improvement in appetite-related hormones (i.e., ghrelin, GLP-1, insulin, leptin, and peptide YY); and (4) to explore whether the two approaches cause different changes in gene expression and metabolic profiles. This is a pilot study conducted at Texas Tech University's Nutrition and Metabolic Health Initiative clinic in Lubbock, Texas. Who can participate: Adults aged 18 years and older with a BMI of 27.5 or higher who are either starting semaglutide or tirzepatide therapy for weight management or who are seeking weight management without the use of weight-loss medications. Who cannot participate: Individuals who are pregnant or lactating, have a pacemaker or internal medical device, have certain serious medical conditions (such as active cancer, uncontrolled hypertension, or severe kidney disease), have type 1 diabetes, or use insulin for type 2 diabetes.

This prospective non-randomized comparative pilot study is conducted at the Nutrition and Metabolic Health Initiative (NMHI) clinic at Texas Tech University in Lubbock, Texas. The study includes two arms: a GLP-1 receptor agonist (GLP-1 RA) arm and a lifestyle (LS) comparator arm. GLP-1 RA arm participants are recruited from obesity medicine and aesthetics clinics in Lubbock, Texas, and enrolled within 0 to 3 days of initiating semaglutide or tirzepatide as prescribed by their own medical provider. LS comparator arm participants are recruited from the community via flyers, community events, hospital intranet postings, and university listservs; they will receive a structured behavioral intervention at no cost. Each arm follows a two-visit assessment schedule at baseline and at three months. In-person visits include anthropometric measurement, bioelectrical impedance analysis for body composition, resting metabolic rate assessment via MedGem indirect calorimetry, blood pressure measurement (average of two readings after a five-minute rest), and venipuncture for biological sample collection. Blood is drawn into serum-separating tubes and an EDTA tube. Serum is processed for lipid panels, basal metabolic panels, hepatic and renal function markers including alanine aminotransferase, aspartate aminotransferase, total bilirubin, and creatinine, as well as appetite-related hormones including ghrelin, GLP-1, insulin, leptin, and peptide YY. The EDTA tube is processed for whole-blood RNA sequencing and untargeted metabolomics. Participants also wear a Garmin device for two weeks following the baseline visit to monitor sleep, heart rate, and oxygen saturation. Online questionnaires are completed via Qualtrics prior to each in-person visit. LS comparator participants receive three individual lifestyle education sessions across the study period: at baseline, at one month, and at two months. Sessions may be completed in person or via a HIPAA-secured video platform and last approximately 30 to 45 minutes each. Each participant's total energy expenditure (TEE) is estimated by multiplying measured resting metabolic rate by a physical activity factor. Participants are instructed to follow a 500 kilocalorie daily deficit from TEE and to accumulate 150 to 300 minutes of moderate-intensity physical activity per week. Meal plans are based on the Academy of Nutrition and Dietetics Nutrition Care Manual. Dietary and physical activity adherence is monitored using MyFitnessPal or a food journal, with records reviewed at each session. Given the pilot nature of this study, the primary emphasis is on effect size estimation and variance characterization to inform future adequately powered trials rather than definitive hypothesis testing. For example, with 12 participants in the GLP-1 receptor agonist arm and 15 participants in the LS comparator arm, the study is powered to detect only large between-group differences in cardiometabolic outcomes. Transcriptomic and metabolomic findings should be interpreted as hypothesis-generating. IRB approval was obtained prior to study initiation (IRB Number: IRB2024-370).