Substrate Metabolism Laboratory

“The Substrate Metabolism Laboratory conducts research centered around diet and exercise, attempting to discover how these factors affect the risk and prevalence of metabolic diseases such as Type 2 diabetes. The health benefits for exercising are well-known, but what is still unclear are the actual mechanisms of diet and exercise that produce healthier lives. By studying and understanding these mechanisms, we will be able to target specific training programs or medications designed to reduce the risk of disease.”
Dr. Jeff Horowitz, Director and Professor of Movement Science

Substrate Metabolism Laboratory


CCRB 1210
401 Washtenaw Ave.
Ann Arbor, MI 48109-2214
(734) 647-3354
(734) 936-1925



Exercise and Fat Cells Study

PURPOSE: The purpose of this study is to measure changes in the cellular composition of adipose tissue after one session of endurance exercise.

ELIGIBLE: This study is limited to healthy men and women, 18-40 years old, who are either a normal weight or overweight (Body Mass Index [BMI] 20-25 or 27-35 kg/m2). We are recruiting people who exercise regularly (i.e. at least 3 days/week of aerobic/cardiovascular exercise for 30-60min/session at moderate and vigorous intensities).  Participants must be weight stable (± 5 lbs. in the past 1 month), must not be taking any medications that affect your metabolism, must not have any evidence or history of cardiovascular or metabolic disease, and must not use tobacco or e-cigarettes.  Female participants must not be pregnant, actively breastfeeding, or menopausal. No racial or ethnic group will be excluded.

PRELIMINARY TESTING: Before participating in the study trial, you will be asked to take part in some tests to determine if you are eligible for the study.  After an overnight fast, you will come to the Substrate Metabolism Laboratory (SML) at the University of Michigan where we will measure your height, weight, body composition, resting metabolic rate, and blood pressure. You will perform an exercise fitness test on a treadmill, and we will measure your insulin sensitivity.  You will also complete a brief physical activity questionnaire and a cardiovascular disease risk questionnaire as part of the preliminary testing.

EXPERIMENTAL TRIAL: If you are eligible, and decide to participate, you will take part in two experimental trials during which we will collect blood and fat tissue samples.  

  • Before each experimental trial (“Pre-trial Visit”). You will be instructed to perform your last regular exercise session 2 days before each experimental  trial. The evening before each experimental trial, you will need report to the SML for a Pre-trial Visit.  Before the “control” experimental trial (non-exercise), you will rest in the lab for one hour. For the “exercise” experimental trial, you will exercise on a treadmill for 1 hour at a moderate intensity.  Following these one hour interventions, you will eat a standardized dinner at a specific time and then will be required to fast overnight.
  • During each experimental trial. The following morning after each pre-trial visit, you will arrive at the Substrate Metabolism Laboratory and will rest quietly for approximately 30 min.  After resting, we will collect a blood sample and take a small sample of fat tissue from your abdomen with a needle. You will then be provided with snacks and discharged.  

COMPENSATION: You will receive $150 for completion of the entire study ($75 for the completion of each experimental trial.  If you do not complete the study you will be compensated at a rate of $10 per hour that you have participated in the study (time in the laboratory). This includes the time to complete the Oral Glucose Tolerance Test, but does not include the time spent completing the other preliminary tests.

To sign up to screen for this study, select “Exercise and Fat Cells Study” on our general screening questionnaire.


Exercise and Overeating Study

PURPOSE: The primary purpose of this study is to examine the effects of 1-week of overeating on important clinical metabolic health outcomes (e.g., glucose tolerance, blood lipid profile, and blood pressure) and factors regulating the structure and metabolic function of fat tissue. This study will determine how regular exercise during this overeating period impacts these responses.

To learn more about this study, and to sign up to be a potential subject for it, read the full description on the Substrate Metabolism Laboratory Studies page.

High Intensity Interval Training (HIIT) Study

PURPOSE: Our overall objectives are to:

  1. Assess mechanisms underlying HIIT-induced improvements in insulin resistance at the whole-body, tissue, and cellular levels; 
  2. Systematically compare different HIIT regimens to help identify effective “doses” of HIIT that may be optimal for improving metabolic health in obese adults; and
  3. Assess the ability/willingness of obese subjects to adhere to a long-term HIIT program.

Findings from these studies will greatly expand our understanding about the effects of HIIT on metabolic health, and will provide valuable information for development of programs aimed at maximizing key metabolic benefits of exercise.

To learn more about this study, and to sign up to be a potential subject for it, read the full description on the Substrate Metabolism Laboratory Studies page.

Protection Against Insulin Resistance (PAIR) Study

PURPOSE: Insulin resistance is a major contributor to the development of several obesity-related diseases. Despite the common link between obesity and insulin resistance, as many as one-third of obese adults appear to be “protected” against insulin resistance. Our preliminary findings indicate that insulin resistance can vary considerably even in a population of obese adults who are very similar in terms of the magnitude and distribution of their adiposity. The overall goal of this project is to identify factors that “protect” some obese adults from becoming insulin resistant. Identifying mechanisms that help protect some obese adults from developing insulin resistance could lead to novel, targeted therapeutic and/or preventative strategies for obese adults who are insulin resistant.

To learn more about this study, and to sign up to be a potential subject for it, read the full description on the Substrate Metabolism Laboratory Studies page.

Iron and Metabolic Health Study

Iron and Metabolic Health Study


Would you like to participate in a study that would improve our understanding of the relationship between iron in the body and insulin resistance?


We are looking for men and women who are:

  • Age 18-40 years
  • Overweight or obese (classified with a Body Mass Index of 27-40 kg/m2)
  • Weight Stable (+/- 6 pounds for past 6 months)
  • Non-tobacco or e-cigarette users
  • Not taking medications or supplements known to affect metabolism or inflammation
  • Relatively healthy with no evidence/history of metabolic diseases or anemia

General blood donation eligibility requirements must be met to participate.  Individuals who have donated blood within the past 12 months will be excluded.  

Women must have regularly occurring menses and be premenopausal.  Pregnant or actively lactating women will be excluded.



Initial Screening – Before participating in the study, you will undergo a physical screening that will include a health history, a food frequency, and a physical activity questionnaire.  We will also obtain your height/weight and take a small sample of blood to measure your hemoglobin concentration. This appointment will take about 1 hour and will take place at the Substrate Metabolism Laboratory (SML) located in the Central Campus Recreation Building (CCRB) at the University of Michigan.  

If you are deemed eligible based on the results of the initial screening, you will be enrolled into our study. The study consists of four (4) distinct phases:

  1. Body Composition Assessment: We will measure your body composition using Dual Energy X-ray Absorptiometry (DEXA scan). Women will provide a urine sample for a urine pregnancy test prior to the DEXA scan.  This visit will take about 30 minutes and will take place at the Michigan Clinical Research Unit (MCRU) located in the Michigan Medicine Cardiovascular Center (CVC).
  2. Baseline Trial:  We want to assess your current level of health.  During this trial we will measure: body weight, resting blood pressure, fat metabolism, insulin sensitivity, and blood lipid profile. These tests will involve blood sampling and we will obtain a small piece of fat from your stomach. You will be required to stay in the hospital for approximately 8 hours.  At this appointment, the study team will provide you with a scale to weigh yourself at home on a daily basis.

NOTE: You will be required to maintain your weight from the baseline trial until the completion of the post-blood donation trial.  If your body weight changes ±4.5 pounds from your baseline trial weight, our research dietitian will provide strategies to help you return to the weight that you measured at your baseline trial.

  1. Blood Donation: You will donate blood about 1 week after your baseline trial at a blood donation center of your choice.  Between 24- and 72-hours following the blood donation, you will return to the SML so we can measure your hemoglobin concentration.  
  2. Post-blood Donation Trial: We will perform all of the same tests that we did at baseline testing described above in order to see how your health has changed after the blood donation.  

PARTICIPATION INCENTIVES: You will receive a total of $300 upon completion of the entire study.  You will not receive compensation for the initial screening, body composition test, or blood donation.  If you do not complete the entire study, you will be compensated at a rate of $10 for each hour spent in the hospital for the study trials.  

To sign up to screen for this study, select “Iron and Metabolic Health Study” on our general screening questionnaire.