Decreased energy density and changes in food selection following Roux-en-Y gastric bypass

Area of Science:

• Bariatric Surgery
• Nutritional Science
• Metabolic Health

Background:

• Obesity is a major health concern requiring effective weight management strategies.
• Roux-en-Y gastric bypass (RYGB) is a common bariatric procedure for significant weight loss.
• Understanding post-surgical dietary changes is crucial for long-term success.

Purpose of the Study:

• To investigate the hypothesis that dietary energy density (DED) decreases after RYGB.
• To assess changes in energy intake (EI) and food weight (FW) following the procedure.
• To explore the relationship between DED changes and percentage weight loss (%WL).

Main Methods:

• A cohort of 43 patients (31 female, 12 male) with a mean BMI of 44.3 kg/m² underwent RYGB.
• Dietary assessments (EI, FW, food choice) were conducted preoperatively and at 6 weeks, 1 year, and 2 years post-surgery.
• DED was calculated as EI divided by FW (kcal/g).

Main Results:

• Significant weight loss was observed at all follow-up points (%WL: 13.5% at 6 weeks, 30.7% at 1 year, 31.8% at 2 years).
• EI decreased significantly post-surgery (P<0.001), while FW showed initial reduction but returned towards baseline by 2 years.
• DED consistently decreased from baseline (1.07 kcal/g) to 0.78 kcal/g at 6 weeks, 0.90 kcal/g at 1 year, and 0.96 kcal/g at 2 years (P<0.001 for all).

Conclusions:

• RYGB leads to a sustained reduction in DED and EI over two years.
• No significant correlation was found between DED reduction and %WL.
• Post-RYGB dietary modifications, including reduced DED, appear nutritionally beneficial despite varying FW and lack of direct correlation with weight loss.