Bariatric surgery may prevent diabetes onset in obese, nondiabetic Asians

Bariatric surgery is beneficial to nondiabetic Asian patients with obesity, delivering sustained weight loss in addition to normalizing sugar levels and insulin resistance within 1–3 years of the procedure, as reported in a Singapore study.

“The last two decades has seen an epidemic of type 2 diabetes (T2D) in Asia. Even at lower body mass index (BMI), Asians are more likely to develop T2D at younger age due to greater prevalence of the metabolically obese phenotype demonstrated by healthy weight but increased abdominal adiposity,” the investigators noted. [Lancet 2006;368:1681-1688; JAMA 2009;301:2129-2140; Lancet 2010;375:408-418]

“Being diagnosed with T2D at a younger age predisposes patients to a greater lifetime risk of cardiorenal complications and malignancy in later life,” they added. “[Bariatric surgery] is a promising modality to prevent or delay the onset of T2D in obese nondiabetic patients.”

The study included 133 patients who underwent bariatric surgery with either sleeve gastrectomy (SG) or laparoscopic Roux-en-Y gastric bypass (LRYGB) between 2009 and 2014. Of the patients, 36.1 percent were Chinese, 33.1 percent Malays, and 21.1 percent Indians. The mean preoperative BMI was 41.7 kg/m², while the mean preoperative HbA1C was 5.66 percent, with fasting glucose of 5.20 mmol/L and C-peptide levels of 958.2 pmol/L. Twenty-nine (21.8 percent) patients had impaired fasting glycaemia.

After the surgery, the mean BMI decreased to 29.9 kg/m² in the first year and then slightly increased to 31.0 kg/m² in the third year. The total weight loss percentage of 27.9 percent at year 1 was maintained at 27.1 percent at year 3. Likewise, fat mass decreased from 47.4 kg at baseline to 27.8 kg and then slightly increased to 33.9 kg after 1 and 3 years, respectively. [Surg Obes Relat Dis 2019;doi:10.1016/j.soard.2019.11.017]

In terms of glycaemic profiles, the mean HbA1C was 5.11 percent at 6 months, 5.08 percent at 1 year and 5.24 percent at 3 years. Glucose levels in all patients who remained on follow-up were kept below 6.0 percent. Additionally, C-peptide levels showed a steady decline after surgery (482 pmol/L at 1 year and 515 pmol/L at 3 years).

Meanwhile, serum fasting insulin levels decreased from 28.36 mU/L at baseline to 6.29 and 6.93 mU/L at the 1- and 3-year follow-up, respectively. Homeostasis model assessment of insulin resistance notably improved from severe insulin resistant state of >5.00 (mean, 7.13) preoperatively to normal ranges of <3.00 (mean, 1.55) at 3 years.

“Given that Asians have more abdominal adiposity as previously discussed and that abdominal adiposity predisposes one to insulin resistance, the effect on insulin resistance reversal may be more pronounced in nondiabetic Asians after bariatric surgery as the extent of insulin resistance may be greater at lower BMIs in Asians compared with Caucasians,” the investigators explained. [JAMA 2009;301:2129-2140; J Clin Invest 2006;116:1793-1801]

“Further studies will have to [be] performed to assess if Caucasians and patients of other ethnic groups will see similar improvements in insulin resistance after bariatric surgery,” they added.

The most important limitation of the study was the relatively high number of patients who were lost to follow-up (57.1 percent and 86.5 percent of the cohort at 1 and 3 years postsurgery, respectively).

Nevertheless, “we observed that nondiabetic obese individuals who are adherent to their follow-up routines after surgery may benefit from delay or prevention of diabetes onset as none of them had been diagnosed with impaired fasting glucose or T2D up to 3 years after surgery,” the investigators said.