Short-term Gain, Long-term Pain? Rate of Weight Loss and Weight Regain following Primary Bariatric Surgery

Cameron Sowter, A/Prof Nicholas Williams

Introduction

Obesity is a worsening public health issue; over two-thirds of Australians are classified as overweight or obese (1,2). Every five-point increase in body mass index above 25 is associated with a 20% increase in all-cause mortality (3). Bariatric surgery remains the most efficacious intervention for obesity. Postoperative
weight regain is expected, however, excess weight regain commonly occurs (4,5,6). Predictive factors for weight regain are debated in literature with age, sex, presence of comorbidities and the percentage of weight loss at various post-operative intervals up to 12 months proposed (7-11).

Aim/Purpose

To investigate whether initial velocity of weight loss is associated with weight regain.

Method/Description

Participants were recruited from a major centre in regional NSW. Retrospective weight data, recorded on a standardised calibrated scale, obtained at baseline (pre operative), months 1, 3, 6 and 12 post-operatively, and annually from 2 to 5 years was used. Weight regain criteria was defined as the percentage of total weight loss (TWL) from nadir, the minimum weight obtained post-operative. Positive or negative TWL10, TWL15 and TWL20 were assigned using the following formula ((total body weight at follow-up – total body weight at nadir) / total body weight at nadir) *100. Initial velocity of weight loss (IVWL) numerical data points were calculated as the percentage of TWL per month, during the months specified. For example, if a patient lost 10% of their initial total weight between month 1 and month 6 post-operatively, their IVWL for months 1 to 6 is -2% per month.

Results

1631 participants were included. Mean participant age was 43.5 (SD 11.2),  79.8% of participants were female and the average pre-operative BMI was 43.0 (SD 7.4). Across the 5 year period 403, 219 and 112 participants were positive for weight regain at TWL10, TWL15 and TWL20 respectively. The rate of weight loss in months 6 to 12 for both TWL15 and TWL20 weight regain criteria were the only statistically significant associations (p<0.05).

Discussion

Rates of weight regain in our population were lower from current publications with 24.7% (n=403) of participants regaining 10% of TWL from nadir, and just 6.9% (n=112) regaining 20% of TWL from nadir. Investigation of association between the three weight regain criteria, weight data time points and IVWL revealed few statistically significant associations, however the IVWL between months 6 to 12 held a significant association with both TWL15 and TWL20. For every unit of increase in IVWL per month across months 6 to12, the odds ratio (OR) of weight regain of TWL15 decreased by 15.6%, and the OR of weight regain of TWL20 decreased by 19.8%. This association highlights the importance of sustained weight loss across months 6 to 12 post-operative, and is an important predictor of weight regain. Clinical implications of findings are clear. Patients with a low rate of weight loss across this time period can be identified early for close monitoring, and potentially counselling on weight loss, as well as additional appointments with a bariatric nurse or dietician to ensure positive weight loss outcomes long-term. Percentage of weight loss in the first 3 postoperative months has previously been associated with maximal weight loss (12,13), while other studies have shown the rate of weight loss across months 3 to 6 postoperative to be a strong predictor of long-term weight loss maintenance, with one study suggesting weight loss at 1 month postoperative may even be predictive (8,12,13).

Conclusions

The initial velocity of weight loss within the first 12 post-operative months reflect varied associations with long-term weight regain. While there was no association with weight loss in months 1 to 3 or 3 to 6, sustained weight loss across months 6 to 12 are associated with avoiding weight regain long-term. Patients with slow weight loss within this period may be identified for additional support to avoid long-term weight regain.

References

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