Introduction:β-aminoisobutyric acid (BAIBA) is a suggested cytokine secreted from skeletal muscles that regulates insulin sensitivity, pancreatic function, and fat oxidation. However, no studies to date have examined if a low-calorie diet (LCD) or LCD + with interval exercise (LCD + INT) differentially raises BAIBA. The purpose was to examine if LCD or LCD + INT raises circulating BAIBA in relation to cardiometabolic health.Methods:For this,twenty-three women with obesity were randomized to either 2-weeks of LCD (n= 12, 48.4 ± 2.5 y, 37.84 ± 1.5 kg/m2; ∼1200 kcal/day) or LCD + INT (n= 11, 47.6 ± 4.3 y, 37.9 ± 2.3 kg/m2; ∼60 min/d of INT alternating 3 min of 90% and 50% HRpeak), with matched energy availability. Fasting BAIBA and adipokines along with glucose, insulin, C-peptide, and FFA after every 30 min up to 120 min were obtained during a 75 g OGTT to estimate total area under the curve (tAUC), insulin sensitivity (SIIS), pancreatic function [disposition index (DI)], and hepatic insulin clearance (HIC). Fuel use (indirect calorimetry) was tested at 0, 60, and 120 min of the OGTT along with fitness (VO2peak) and body composition (BodPod).Results:Both treatments lowered body weight (p< 0.001) and leptin (p< 0.001) but raised BAIBA (p =0.007) and insulin sensitivity (p= 0.02). LCD + INT increased VO2peak (p= 0.02) and REE tAUC120min(p =0.02) while LCD and LCD + INT decreased carbohydrate oxidation (CHOox) tAUC120min(p< 0.001). Increased BAIBA associated with reduced weight (r= −0.67,p< 0.001), leptin (r= −0.66,p= 0.001), CHOoxtAUC120min(r= −0.44,p= 0.03) and DImuscle120min(r= −0.45,p= 0.03), but elevated HIC120min(r= 0.47,p= 0.02).Discussion:Concluding, LCD and LCD + INT increased BAIBA in relation to reduced body weight and pancreatic function in women with obesity. This suggests energy deficit is a key factor regulating circulating BAIBA.