Aim: Bariatric surgery induces significant weight loss, increases insulin sensitivity, and reduces mortality, but the underlying mechanisms are not clear. It was hypothesized that Roux‐en‐Y gastric bypass (RYGB) surgery improves metabolic profile along with weight loss. The objective of this pilot study was to evaluate changes in serum metabolites and fatty acids (FA) at 2 weeks and 6 months after RYGB.Materials and Methods: Serum samples were collected pre‐surgery, at 2 weeks and 6 months post‐surgery from 20 patients undergoing RYGB surgery. Serum non‐esterified free FA (NEFA) were measured. Serum metabolites and FA were measured using nuclear magnetic resonance spectroscopy and improved direct fatty acid methyl ester synthesis and the gas chromatography/mass spectrometry method, respectively, in subjects who completed follow‐up at 6 months (n = 8).Results: Mean (standard deviation) percent total weight loss was 6.70% (1.7) and 24.91% (6.63) at 2 weeks (n = 15) and 6 months (n = 8) post‐surgery, respectively. NEFA were significantly reduced at 6 months post‐surgery (P = 0.001, n = 8). Serum branched chain amino acids, 2‐aminobutyrate, butyrate, 2‐hydroxybutyrate, 3‐hydroxybutyrate, acetone, 2‐methylglutarate, and 2‐oxoisocaproate were significantly reduced, while serum alanine, glycine, pyruvate, and taurine were significantly elevated at 6 months post‐surgery compared with pre‐surgery (n = 8, P < 0.05). Also, serum FA C10:0, C13:0, C14:0, C15:0, and C18:0 increased significantly (n = 8, P < 0.05) by 6 months post‐surgery.Conclusions: Changes in serum metabolites and FA at 6 months post‐RYGB surgery in this pilot study with limited number of participants are suggestive of metabolic improvement; larger studies are warranted for confirmation.

Background: The effects of time-restricted eating (TRE) with exercise on body composition in adults are not clear. Objective: This meta-analysis aimed to assess the effects of TRE when followed in combination with various forms of exercise, including aerobic, resistance, and combined aerobic and resistance [concurrent] training on body composition. Methods: Studies published up to May 2023 were searched in EBSCOhost (MEDLINE, CINAHL, SPORTSDISCUS), PubMed, and SCOPUS databases. Fifteen studies, including 338 participants, that evaluated TRE vs. unrestricted eating in individuals performing exercise were analyzed. A random-effects model was used to calculate the weighted mean effect sizes (ES) with 95% confidence intervals (95% CI’s). Results: According to the pooled results, TRE had a small but significant reduction of fat mass (FM) kg with an effect size of −0.20 (95% CI = −0.28 to −0.13, p < 0.001) and on body fat percent (BF%) with an effect size of −0.23 (95% CI = −0.35 to −0.11, p < 0.001). The prediction interval ranged from −0.48 to 0.08 for FM and from −0.64 to 0.18 for BF%, respectively. TRE did not significantly alter fat-free mass (FFM) kg compared to control (p = 0.07). Furthermore, age, body mass index (BMI), exercise type, study duration, and energy intake did not have a significant impact on the variation in effect sizes according to the subgroup analyses (p > 0.05). Conclusion: TRE with exercise may reduce fat mass compared to an unrestricted eating window exercise-matched control while preserving FFM. However, more studies are needed.