Harnessing Macrophage Lysosomal Lipid Metabolism in Obesity

The goal of this study is to evaluate the role of transcription factor EB (TFEB) in adipose (fat) tissue macrophages (ATM) in regulating adipose tissue and systemic metabolic function in obesity. The investigators will assess the differences in ATM lipid metabolism in people with metabolically abnormal obesity and lean individuals. Both groups will have: * screening visit * imaging (body composition testing - dual-energy x-ray absorptiometry (DEXA) scans, magnetic resonance imaging \[MRI\] and magnetic resonance spectroscopy \[MRS\] scans) * Overnight visit with intravenous infusion (IV), muscle, and fat tissue biopsies Participants with obesity will complete meetings with study team members for a weight loss intervention to achieve a 10% body weight loss.

Inclusion Criteria : * age: ≥18 but ≤70 years * not pregnant or breastfeeding * weight stable and sedentary before enrollment * no use tobacco products, excessive amounts of alcohol, or dietary supplements, or medications known to or suspected to affect glucose and lipid metabolism (aside from certain medications used to treat diabetes in the metabolically abnormal obesity \[MAO\]-Type 2 Diabetes group) * no evidence of significant organ system dysfunction or disease (e.g. chronic severe kidney disease, cancer) * participants must fulfil all of the following group-specific inclusion criteria below: Lean group: * Body mass index (BMI) ≥18.5 but \