How Metabolism Affects Weight Loss and Gain

Summary

This study examines why some individuals with obesity have difficulty losing weight, whereas some lean individuals struggle to gain weight. The investigators will measure how the human body uses energy during a fasting period and after consumption of a specially designed, low-protein meal. By comparing these responses, the investigators aim to identify different "metabolic phenotypes" that affect weight control. Findings from this research may lead to more personalized treatments for managing weight. Participation in this study involves simple tests and basic body measurements.

Eligibility

Inclusion Criteria:

* Group 1 (Lean): BMI 18.5-22.0 kg/m², reporting difficulty gaining weight
* Group 2 (Obese): BMI \>30 kg/m², reporting difficulty losing weight
* Healthy status as determined by medical history, physical examination, and laboratory tests
* Stable weight (less than 5% fluctuation) over the past 6 months

Exclusion Criteria:

* Prediabetes (HbA1c \>5.6% or fasting blood glucose \>100 mg/dL) or diabetes mellitus
* Conditions affecting appetite or energy expenditure (e.g., Cushing's syndrome, uncontrolled hyper-/hypothyroidism)
* Gastrointestinal disorders that impact nutrient absorption (e.g., inflammatory bowel disease, malabsorption syndromes, ulcers)
* Psychiatric conditions influencing eating behavior (e.g., active depression, anorexia nervosa, bulimia nervosa, borderline personality disorder)
* Acute, unstable cardiovascular disease requiring hospitalization within the last 6 months (e.g., stent placement)
* Cancer that required treatment in the past 5 years
* Chronic kidney disease (Stage IV or higher, per NKF criteria)
* Active infectious disease (e.g., HIV, hepatitis)
* Current nicotine use or nicotine use within the last month prior to screening
* Illicit drug use (e.g., amphetamines, cocaine, heroin, marijuana)
* Regular high-intensity physical activity (≥1 hour/day)
* Non-MRI-compatible metallic implants (e.g., artificial joints, metal plates)
* Pregnancy or breastfeeding
* Use of weight-loss medications
* Clinically significant claustrophobia
* Any other condition not mentioned above that, in the opinion of the investigator, could interfere with study participation or compromise patient safety

Conditions2

Browse More Trials