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The Impact of Bariatric Surgery on Nitrogen Balance at Six months Post-surgery

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Abstract

Purpose

Obesity, defined as abnormal or excessive fat accumulation that presents a risk to health, rose from 8.6 to 10.5% in Singapore’s residents. Bariatric surgery, the primary treatment for severe obesity, induces fat and muscle loss. Adequate protein intake is vital for preventing muscle loss. This study examines nitrogen balance in individuals with obesity pre- and post-surgery.

Materials and Methods

Sixteen participants with severe obesity (BMI ≥ 32.5 kg/m2) undergoing bariatric surgery (14 sleeve gastrectomy, 2 Roux-en-Y gastric bypass) and 20 normal-weight controls (BMI < 25 kg/m2) were recruited. Nitrogen balance, calculated from dietary protein intake and urine nitrogen excretion, was assessed. Participants with obesity were re-evaluated 6 months post-surgery. Data were analyzed using parametric methods.

Results

At baseline, controls had a BMI of 20.8 ± 2.1 kg/m2; those with obesity had 40.9 ± 7.3. Daily calorie and protein intake for participants with obesity were not statistically significantly different from controls (calorie intake at 1467 ± 430 vs. 1462 ± 391 kcal, p = 0.9701, protein intake 74.2 ± 28.7 vs. 64.6 ± 18.3 g, p = 0.2289). Post-surgery, BMI, fat-free mass, fat mass, total energy intake, carbohydrate, and protein intake decreased significantly (p < 0.01). Protein oxidation and urine nitrogen excretion did not change after bariatric surgery. However, nitrogen balance significantly reduced from 2.62 ± 5.07 to − 1.69 ± 5.07 g/day (p = 0.025).

Conclusion

Dietary protein intake is inadequate in individuals with obesity at 6 months post-bariatric surgery and contributes to a state of negative nitrogen balance.

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Data Availability

The data that support the findings of this study are available on request from the corresponding author.

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Author information

Authors and Affiliations

  1. Duke-NUS Medical School, Singapore, 169857, Singapore

    Ramalakshmi Gayathri Vinjamuri & Jean-Paul Kovalik

  2. Department of Endocrinology, Singapore General Hospital, Singapore, 169608, Singapore

    Vieon Wu, Phong Ching Lee & Hong Chang Tan

  3. Department of Upper Gastrointestinal and Bariatric Surgery, Singapore General Hospital, Singapore, 169608, Singapore

    Alvin Eng, Jeremy Tan & Eugene Lim

Authors
  1. Ramalakshmi Gayathri Vinjamuri
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  2. Vieon Wu
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  3. Alvin Eng
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  4. Jeremy Tan
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  5. Eugene Lim
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  6. Phong Ching Lee
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  7. Jean-Paul Kovalik
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  8. Hong Chang Tan
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Corresponding author

Correspondence to Hong Chang Tan.

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Ethics Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the IRB at SingHealth and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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Informed consent was obtained from all individual participants included in the study.

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The authors declare no competing interests.

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Key points

• Bariatric surgery resulted in significant loss of fat-free mass.

• Protein oxidation rates did not change following bariatric surgery.

• Dietary protein intake was reduced post-surgery and resulted in a negative nitrogen balance.

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Vinjamuri, R.G., Wu, V., Eng, A. et al. The Impact of Bariatric Surgery on Nitrogen Balance at Six months Post-surgery. OBES SURG (2024). https://doi.org/10.1007/s11695-024-07269-3

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  • DOI: https://doi.org/10.1007/s11695-024-07269-3

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