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Post-surgical control deficits

Inhibitory control responsible for unsatisfactory weight loss

The researchers investigated the performance of two tasks that assess inhibitory control or response interference control differ between female patients who did not maintain weight after RYGB-surgery and those who successfully maintained their weight loss
The poor responders (vs. good responders) needed significantly more time when conducting a go/no-go task (p=0.03)

Patients who have poor poorer inhibitory lose less weight after RYGB-surgery and it is suggested that cognitive behavioural therapies after surgery could be a “promising behavioural adjuvant to achieve sustainable weight loss in patients undergoing this procedure”. The paper, published in PlosOne, recommends that future studies should examine whether such control deficits in poor responders are “food-specific or not”.

Although Roux-en-Y gastric bypass (RYGB) surgery results in considerable and satisfactory weight loss for many, nevertheless, some patients have poor long-term weight loss after and one suggestion is an impairment of cognitive control that impedes this patient group’s dietary efforts.

Therefore, the researchers from Uppsala University, Uppsala, Sweden investigated the performance of two tasks that assess inhibitory control or response interference control (ie. Go/no-go task and Stroop interference task) differ between female patients who did not maintain weight after RYGB-surgery (poor responders) and those who successfully kept their weight after the procedure (good responders). 

Study

A total of 15 female patients with a good weight-loss response (‘good responders’) and 15 female patients with a poor weight-loss response after RYGB-surgery (‘poor responders’) who underwent primary RYGB-surgery at the University Hospital of Uppsala 1993–2003.

Poor responders were defined as patients with an excessive weight and BMI loss of <50% (between 9–15y after surgery) and BMI>30; good responders as patients with an excessive weight and BMI loss of >75% and BMI<30. Responders were pair-wise matched with poor responders for preoperative BMI (±2 BMI units), preoperative weight (±10 kg) and age (±5 years).

Participants visited the research centre to conduct the tests as described below. Most visits were scheduled in the afternoon in a fasted state, i.e. at least 1.5 hrs after lunch. For logistic reasons, data of two poor responders and two good responders were collected in a sated state.

A go/no-go association task was used to assess the inhibition of pre-potent responses to food items. In this task, words of non-food items (go-trial) or words of food items (no-go-trial) were presented for 500ms. Response interference control was measured using a modified version of a Stroop colour-naming interference task. Participants were presented a series of food-related words printed in different colours. They were instructed to name the colour in which each word was printed as quickly as possible, i.e. to inhibit the pre-potent reading response. The 21-item Three Factor Eating Questionnaire (TFEQ-R21) was used to assess uncontrolled- eating, restraint-eating, and emotional-eating [25], and the 30-item Barratt Impulsivity Scale (BIS-11) to measure total impulsiveness, as well as motor, non-planning and attentional impulsiveness.

Outcomes

In the go/no-go task the average response time to ‘go’ stimuli differed across groups: poor responders were slower than good responders (p=0.03; Fig. 1A). The number of commission errors and omission errors did not differ across groups: poor vs. good responders made 7.5±5.5 vs. 8.1±3.2 commission errors and 0.9±1.6 vs. 1.8±0.9 ommission errors. Stroop task performance also differed across groups: poor responders performed worse than good responders (p=0.002; Fig. 1B).

Figure 1: Performance on go/no-go task and Stroop interference task by patients who showed a poor weight loss response to gastric bypass (RYGB) surgery ~ 12 years after surgery (poor responders, n = 15, black bars) and patients who responded well to RYGB-surgery ~ 12 years after surgery (good responders, n = 15, white bars). (A) Average response time to ‘go’ stimuli (i.e. non-food-related words as opposed to food words as ‘no-go’ stimuli). (B) Performance on the food-related Stroop interference task. All groups were matched for pre-operative weight/BMI, educational status and age *P<0.05 for significant differences between poor and good responders.

Scores on TFEQ-subscales, BIS-11 impulsivity, and BIS-11 subscales were not different between good and poor responders. However, scores for uncontrolled eating (TFEQ) were associated with inferior weight loss (kg) ~12 years after surgery (p=0.025). A similar trend was seen for attentional impulsiveness (BIS-11) and weight loss (p=0.067).

The poor responders (vs. good responders) needed significantly more time when conducting a go/no-go task (p=0.03), but the number of errors did not differ between groups. When conducting a Stroop interference task, poor responders read fewer inks than good responders (p=0.002).

“Our study demonstrates that female patients lacking sustainable weight loss approximately 12 years after RYGB-surgery (‘poor responders’) performed worse on the go/no go task and Stroop task, when compared to patients with a good sustainable weight after RYGB-surgery (‘good responders’),” the authors state. “These results suggest that food cues possess a distracting value for poor responders after the surgery…Taken together, these results suggest that cognitive traits related to eating behaviour may impact surgery-induced weight loss response.”

“Patients with a poor long-term weight loss response after RYGB-surgery performed worse on the go/no-go task and the Stroop task than patients who did successfully maintain weight loss,” the authors conclude. “The results of the present study provide a rationale for hypothesising that post-RYGB surgery therapies targeting cognitive control may represent a promising behavioural adjuvant to achieve sustainable weight loss in patients undergoing this procedure.”

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